U.S. patent application number 11/899313 was filed with the patent office on 2008-01-03 for system for standard positioning service and precise positioning service cooperative operation.
Invention is credited to Michael P. Dentinger, Ken Spratlin.
Application Number | 20080001813 11/899313 |
Document ID | / |
Family ID | 34710630 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080001813 |
Kind Code |
A1 |
Dentinger; Michael P. ; et
al. |
January 3, 2008 |
System for standard positioning service and precise positioning
service cooperative operation
Abstract
A system for standard positioning service (SPS) and precise
positioning service (PPS) cooperative operation is disclosed. In
one embodiment, a PPS receiver is utilized to process a PPS data
portion of a positioning signal. In addition, an SPS receiver is
utilized to process an SPS data portion of the positioning signal.
Furthermore, the PPS receiver and the SPS receiver are
communicatively coupled such that the PPS data portion from the PPS
receiver is cross-validated with the SPS data portion from the SPS
receiver thereby corroborating the accuracy of the positioning
signal.
Inventors: |
Dentinger; Michael P.; (Los
Altos, CA) ; Spratlin; Ken; (Boulder, CO) |
Correspondence
Address: |
Wagner Blecher LLP
123 Westridge Drive
Watsonville
CA
95076
US
|
Family ID: |
34710630 |
Appl. No.: |
11/899313 |
Filed: |
September 4, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10745829 |
Dec 24, 2003 |
7283090 |
|
|
11899313 |
Sep 4, 2007 |
|
|
|
Current U.S.
Class: |
342/357.41 |
Current CPC
Class: |
G01S 5/0072 20130101;
G01S 19/25 20130101; G01S 19/32 20130101; G01S 19/215 20130101;
G01S 19/18 20130101; G01S 19/20 20130101 |
Class at
Publication: |
342/357.06 |
International
Class: |
G01S 1/02 20060101
G01S001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2004 |
US |
PCT/US04/40954 |
Claims
1. A system for standard positioning service (SPS) and precise
positioning service (PPS) cooperative operation comprising: a PPS
receiver to process a PPS data portion of a positioning signal; and
an SPS receiver to process an SPS data portion of the positioning
signal, wherein the PPS receiver and the SPS receiver are
communicatively coupled such that the PPS data portion from the PPS
receiver is cross-validated with the SPS data portion from the SPS
receiver thereby corroborating the accuracy of the positioning
signal.
2. The system of claim 1 wherein the SPS data portion of the
positioning signal is CA code on an L1 band.
3. The system of claim 1 wherein the PPS data portion of the
positioning signal is P code or encoded Y code on the L1 band or an
L2 band.
4. The system of claim 1 wherein during the cross-validating of the
PPS data portion with the SPS data portion, the PPS data portion is
selected as the correct data portion if the cross-validation does
not result in a corroboration of the accuracy of the positioning
signal.
5. The system of claim 1 wherein the PPS receiver includes a KDP
(key data processor) adapted to receive a CV (crypto variable) from
an external keying device, the KDP operable for generating Crypto
Variable Anti Spoofing (Cvas) and selective availability (SA)
correction information.
6. The system of claim 1 wherein the PPS receiver and the SPS
receiver each have a distinct antennae for receiving the
positioning signal.
7. The system of claim 1 wherein the PPS receiver and the SPS
receiver utilize the same antenna for receiving the positioning
signal.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of and claims the benefit
of co-pending U.S. patent application Ser. No. 10/745,829 filed on
Dec. 24, 2003 entitled "system for standard positioning service and
precise positioning service cooperative operation" by Michael P.
Detinger et al., which is assigned to the assignee of the present
invention, and is hereby incorporated by reference in their
entirety herein.
TECHNICAL FIELD
[0002] The present invention relates generally to positioning and
navigation systems. More specifically, the present invention
pertains to a system for implementing a precise positioning service
global positioning receiver in cooperation with a standard position
service global positioning receiver.
BACKGROUND ART
[0003] The aviation industry relies upon numerous navigation aids
in order safely to take off, navigate enroute, and land aircraft.
Such navigation aids (naviads) include, for example, the instrument
landing system (ILS), very high frequency omni-directional range
(VOR) system, and the like. The survey industry also relied upon
numerous location aids in order to ensure the most precise
measurements are being performed. The Navstar Global Positioning
System, hereafter referred to simply as GPS, is increasingly being
accepted as an alternative to traditional navigation and survey
aids. In addition to civilian applications, GPS is being used
extensively by the United States Department of Defense (DOD) to
provide military users with highly accurate position, velocity, and
time information.
[0004] GPS is a space based radio positioning network for providing
users equipped with suitable receiver's highly accurate position,
velocity, and time (PVT) information. Developed by the United
States Department of Defense (DOD), the space based portion of GPS
comprises a constellation of GPS satellites in non-geosynchronous
12-hour orbits around the earth.
[0005] Prior art FIG. 1 shows the constellation 100 of GPS
satellites 101 in orbit. The GPS satellites 101 are located in six
orbital planes 102 with four of the GPS satellites 101 in each
plane, plus a number of "on orbit" spare satellites (not shown) for
redundancy. The orbital planes 102 of the GPS satellites 101 have
an inclination of 55 degrees relative to the equator and an
altitude of approximately 20,200 km (10,900 miles) and typically
complete an orbit in approximately 12 hours. The positions of GPS
satellites 101 are such that a minimum of five of the GPS
satellites 101 are normally observable (above the horizon) by a
user anywhere on earth at any given time.
[0006] GPS position determination is based upon a concept referred
to as time of arrival (TOA) ranging. Each of the orbiting GPS
satellites 101 broadcasts spread spectrum microwave signals encoded
with positioning data and satellite ephemeris information. The
signals are broadcast on two frequencies, L1 at 1575.42 MHz and L2
at 1227.60 MHz, modulated using bi-phase shift keying techniques.
Essentially, the signals are broadcast at precisely known times and
at precisely known intervals. The signals are encoded with their
precise time of transmission. A user receives the signals with a
GPS receiver designed to time the signals and to demodulate the
satellite orbital data contained in the signals. Using the orbital
data, the GPS receiver determines the time between transmission of
the signal by the satellite and reception by the receiver.
Multiplying this by the speed of light gives what is termed the
pseudo range measurement of that satellite. If the GPS receiver
clock were perfect, this would be the range measurement for that
satellite, but the imperfection of the clock causes it to differ by
the time offset between actual time and receiver time. Thus, the
measurement is called a pseudo range, rather than a range. However,
the time offset is common to the pseudo range measurements of all
the satellites. By determining the pseudo ranges of four or more
satellites, the GPS receiver is able to determine its location in
three dimensions, as well the time offset. Thus, a user equipped
with a proper GPS receiver is able to determine his PVT with great
accuracy, and use this information to navigate safely and
accurately from point to point, among other uses.
[0007] In addition to the well-known civilian applications
discussed above, GPS is being used extensively by the DOD (e.g.,
Air Force, navy, army, etc.). The increased accuracy of GPS based
navigation and position determination enables the more efficient
utilization of military assets. For example, GPS based PVT enable
the more coordinated maneuvering of platforms (e.g., ships,
aircraft, land vehicles, etc.), more accurate assessment of
opposing force deployments, the more accurate delivery of unguided,
or "dumb" weapons, and the accurate guidance and targeting of
precision guided "smart" weapons.
[0008] One of the most rapidly increasing civilian and military
applications of GPS is the employment of GPS receivers directly in
the field for both survey and location applications. Such GPS
receivers are broken into two basic categories, standard
positioning service (SPS) receivers and precise, or protected
positioning service (PPS) receivers. SPS receivers are utilized in
the civilian GPS market while PPS receivers are utilized in the DOD
environment. In general, SPS receivers do not contain cryptographic
data and are therefore not as accurate as PPS receivers.
[0009] DOD GPS applications require the most accurate PVT possible.
These applications also need to be secure from jamming spoofing and
other types of countermeasures. As is well known, PPS is a high
accuracy (e.g., published specifications to 6 meters 1DRMS
horizontal, or 16 meters CEP) service used by DOD authorized users
(e.g., the military). PPS is based upon processing P code signals
modulated on both the L1 frequency and the L2 frequency. When
encrypted, as in times of war, the P code becomes the Y code,
necessitating the use of special crypto keys available only to DOD
authorized users using specialized GPS receiver equipment.
[0010] Prior Art FIG. 2 shows a typical prior art PPS receiver
system 200. System 200 shows the specialized encryption receiver
components utilized in generating the encoded Y code signal. As is
well known in the art, a replica of the Y code signal must be
generated by a GPS receiver in order to achieve a lock on the Y
code signal transmitted from the respective GPS satellites. System
200 depicts the components required to generate the Y code signal
replica.
[0011] As shown in FIG. 2, system 200 includes a P code generator
201 coupled to a Y code generator 202 via line 204. Y code
generator 202 is coupled to a KDP 208 (key data processor) via line
207. KDP 208 is also coupled to a CV 205 (crypto-variable) keying
device and a computer system 211 via line 206 and line 209.
[0012] System 200 functions by generating a Y code replica for use
by an incorporating GPS receiver in locking onto a transmitted Y
code signal from a GPS satellite. As is well known, a Y code is
generated by properly encrypting the P code. P code generator 201
generates a replica P code and couples this P code to Y code
generator 202 via line 204. Y code generator 202 encrypts this P
code using a CVas (crypto variable anti spoof) key received from
KDP 208 via line 207. Y code generator 202 generates the Y code 210
by encrypting the P code using the CVas key provided by KDP 208.
The Y code 210 is coupled to a DSP 220 where it is used to process
Y code signals received from the GPS satellites via antenna 222 and
RF front end 221. The resulting positioning information is
subsequently coupled to the computer system 211 via line 223. KDP
208 also couples SA corrections to computer system 211 via line 209
which allows the computer system 211 to cancel out the PVT errors
due to selective availability (SA).
[0013] The KDP 208 functions by generating the CVas key used by Y
code generator 202. As is known by those skilled in the art, KDP
208 generates the CVas by using a CV (crypto-variable) key 205. The
KDP 208 thus generates the CVas key from the CV key 205. Thus,
system 200 enables the incorporating GPS receiver to decode and
process the encrypted Y code signals from the GPS
constellation.
[0014] Only users equipped with GPS receivers which incorporate Y
code hardware (e.g., KDP 208, and Y code generator 202) and which
have current CV keys are able to process the Y code signals.
Consequently, access to the CV keys are very tightly controlled. In
addition, the design of the encrypting hardware of KDPs (e.g., KDP
208) is very tightly controlled. This high level of control greatly
increases the cost of fielding and maintaining an inventory of PPS
receivers.
[0015] In addition, current KDPs are typically implemented as chip
sets of three or more discreet integrated circuits. Accordingly,
the KDP accounts for a significant portion of the cost of the PPS
receiver. The multi chip KDP implementation also increases the
complexity of a PPS receiver, its ability to be tested, and the
like. These are all disadvantages when the objective is to use
highly accurate and cost effective PPS receivers in the military,
especially in the case of disposable PPS receivers for use with
PGMs.
[0016] Due to the complexity and associated cost of the PPS
receiver, the technology of the PPS receiver is years behind that
of the civilian SPS receiver. Therefore, most advances with GPS
based technology occurs on the civilian SPS side of the GPS market.
Due to the dissimilar advances in GPS technology, the SPS receiver
is more technologically (e.g., software and hardware) advanced that
that of the PPS receiver. That is, the SPS receiver may contain
newer technology, require less power to function, and be able to
operate more advanced software than that of the PPS receiver.
[0017] Thus, what is needed is a system for SPS and PPS cooperative
operation. What is also needed is a system for SPS and PPS
cooperative operation which allows the better applications of the
civilian SPS receiver to operate in the more accurate DOD
environment of the PPS receiver. What is further required is a
system which provides these advantages without compromising
accuracy, integrity, or security.
DISCLOSURE OF THE INVENTION
[0018] Embodiments of the present invention provide a system for
SPS and PPS cooperative operation. Embodiments of the present
invention also provide a system for SPS and PPS cooperative
operation which allows the better applications of the civilian SPS
receiver to operate in the more accurate DOD environment of the PPS
receiver. Embodiments of the present invention further provide a
system which provides these advantages without compromising
accuracy, integrity, or security.
[0019] In one embodiment, a system for standard positioning service
(SPS) and precise positioning service (PPS) cooperative operation
is disclosed. In one embodiment, a PPS receiver is utilized to
process a PPS data portion of a positioning signal. In addition, an
SPS receiver is utilized to process an SPS data portion of the
positioning signal. Furthermore, the PPS receiver and the SPS
receiver are communicatively coupled such that the PPS data portion
from the PPS receiver is cross-validated with the SPS data portion
from the SPS receiver thereby corroborating the accuracy of the
positioning signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings, which are incorporated in and
form a part of this specification, illustrate embodiments of the
invention and, together with the description, serve to explain the
principles of the invention:
[0021] Prior Art FIG. 1 shows a constellation of GPS satellites in
orbit.
[0022] Prior Art FIG. 2 shows a prior art PPS system.
[0023] FIG. 3 shows a flow chart of a method for SPS and PPS
cooperative operation in accordance with one embodiment of the
present invention.
[0024] FIG. 4 illustrates one embodiment of the levels of possible
SPS and PPS cooperative operation in accordance with one embodiment
of the present invention.
[0025] FIG. 5 is a flow chart of a method for standard positioning
service and precise positioning service cooperative operation in
accordance with one embodiment of the present invention.
[0026] FIG. 6 shows a computer system in accordance with one
embodiment of the present invention.
[0027] FIG. 7A is a block diagram of a system for standard
positioning service and precise positioning service cooperative
operation having a separate antennae configuration in accordance
with one embodiment of the present invention.
[0028] FIG. 7B is a block diagram of a system for standard
positioning service and precise positioning service cooperative
operation having a shared antenna configuration in accordance with
an embodiment of the present invention.
[0029] FIG. 8A is a block diagram of a system for standard
positioning service and precise positioning service cooperative
operation having a separate antennae configuration and a controller
in accordance with one embodiment of the present invention.
[0030] FIG. 8B is a block diagram of a system for standard
positioning service and precise positioning service cooperative
operation having a shared antenna configuration and a controller in
accordance with an embodiment of the present invention.
[0031] FIG. 9 is a block diagram of a system for standard
positioning service and precise positioning service cooperative
operation having a shared antenna configuration and a personal
computer memory card interface architecture (PCMCIA) configuration
in accordance with one embodiment of the present invention.
[0032] FIG. 10 is a block diagram of a system for standard
positioning service and precise positioning service cooperative
operation having a survey configuration in accordance with one
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0033] Reference will now be made in detail to the preferred
embodiments of the invention. While the invention will be described
in conjunction with the preferred embodiments, it will be
understood that they are not intended to limit the invention to
these embodiments. On the contrary, the invention is intended to
cover alternatives, modifications and equivalents, which may be
included within the spirit and scope of the invention as defined by
the appended claims. Furthermore, in the following detailed
description of the present invention, numerous specific details are
set forth in order to provide a thorough understanding of the
present invention. However, the present invention may be practiced
without these specific details. In other instances, well-known
methods, procedures, components, and circuits have not been
described in detail so as not to unnecessarily obscure aspects of
the present invention.
[0034] Some portions of the detailed descriptions which follow are
presented in terms of procedures, logic blocks, processing, and
other symbolic representations of operations on data bits within a
computer memory. These descriptions and representations are the
means used by those skilled in the data processing arts to most
effectively convey the substance of their work to others skilled in
the art. A procedure, logic block, process, step, etc., is here,
and generally, conceived to be a self-consistent sequence of steps
or instructions leading to a desired result. The steps are those
requiring physical manipulations of physical quantities. Usually,
though not necessarily, these quantities take the form of
electrical or magnetic signals capable of being stored,
transferred, combined, compared, and otherwise manipulated in a
computer system. It has proven convenient at times, principally for
reasons of common usage, to refer to these signals as bits, values,
elements, symbols, characters, terms, numbers, or the like.
[0035] It should be borne in mind, however, that all of these and
similar terms are to be associated with the appropriate physical
quantities and are merely convenient labels applied to these
quantities. Unless specifically stated otherwise as apparent from
the following discussions, it is appreciated that throughout the
present invention, discussions utilizing terms such as "receiving"
or "processing" or "decrypting" or "encrypting" or "decoding" or
"encoding" or "acquiring" or the like, refer to the action and
processes of a computer system, or similar electronic computing
device, that manipulates and transforms data represented as
physical (electronic) quantities within the computer system's
registers and memories into other data similarly represented as
physical quantities within the computer system memories or
registers or other such information storage, transmission or
display devices.
[0036] Referring now to FIG. 3, a flowchart 300 of the method for
standard positioning service (SPS) and precise positioning service
(PPS) cooperative operation is shown in accordance with one
embodiment of the present invention. In general, embodiments of the
present invention allow a user to utilize the more advanced aspects
of a civilian (SPS) GPS receiver while maintaining the accuracy of
the DOD (PPS) GPS receiver. Specifically, due to the advances in
the civilian GPS receiver market, many aspects of GPS capabilities
(e.g., land survey, aviation, location, interactive maps, two
antenna blade control systems for machine control, differential
capable systems that utilize multiple differential sources such as
Coast Guard, L-band, radio link, and the like) are available in a
better format in an SPS receiver than in a PPS receiver. However,
in some cases the positioning signals accessible to an SPS receiver
may be malfunctioning, jammed, spoofed, or the like. Therefore, by
allowing the PPS receiver (which is capable of both seeing more GPS
devices as well as operating in a cryptographic mode) to be
cross-validated with the SPS data portion from the SPS receiver,
information may be provided about the validity of the positioning
signal received to the SPS receiver. For example, the raw data
received by the SPS and PPS receivers may be compared to ensure
that both receivers are receiving the same information. In addition
to seeing more GPS devices, the PPS receiver also maintains a
higher anti-jamming/interference suppression, and anti-spoofing
capability than that of the SPS receiver. Furthermore, as described
herein, the PPS receiver has full access to the L2 band and
protected data, while the SPS receiver may access only the L1 band.
The use of GPS as the format for providing the positioning signal
is merely for purposes of brevity and clarity. The present
invention is well suited for utilization with any device or network
which provides a positioning signal (e.g., GLONASS, WAAS, or the
like).
[0037] In one embodiment, cross-validation may be used to ensure
that the SPS receiver is not being spoofed. For example, a
non-friendly positioning signal (e.g., spoofing signal,
purposely-wrong signal, or malfunctioning device signal) may be
being broadcast. This signal may be able to correctly mimic the CA
code to throw the accuracy of the SPS receiver off. In a worse
case, the non-friendly signal may completely stop the SPS receiver
from acquiring its position at all. However, a PPS receiver having
a higher security classification than the SPS receiver may be able
to utilize its cryptographic capabilities, better positioning
signal reception, and the P (or Y) code to correctly locate itself.
Therefore, by cross-validating the raw data (or the pseudo ranges,
or any of the other data fields described herein) between the two
receivers the non-friendly signal may be identified and removed
from the situation.
[0038] For example, the PPS receiver may track the PPS service
positioning signals and provide data aiding to a commercial SPS
receiver. This may aid the SPS receiver in many phases of operation
including the prevention from tracking intentionally or
unintentionally erroneous GPS signals (e.g., GPS like signals with
any combination of identical or invalid pseudorandom code,
navigation message, received signal strength, and carrier/code
Doppler rates from transmitters or repeaters). In the military
marketplace, intentional generation of these erroneous positioning
signals is called "spoofing," and this mitigation functionality is
referred to herein as anti-spoofing.
[0039] The PPS receiver (based on its own processing capability or
based on information provided by a host system with access to
trusted data) provides integrity and data in the form of a "track
list" providing a list of satellite identification, code/carrier
value, Doppler rates, received signal quality (C/No or equivalent),
jamming signal strength, other tracking data, and track history for
valid GPS signals that the SPS receiver should track. In addition,
the PPS receiver provides integrity and data in the form of a "do
not track list" providing the same information for invalid GPS
signals that the SPS receiver should not track. The PPS receiver
may also provide any other GPS data or signal information acquired
from the PPS receiver which may be used to aid the SPS receiver in
many phases of operation. The SPS receiver may then process the
integrity data to ensure that it is not processing invalid GPS
signals.
[0040] Thus, the method for cross-validating PPS and SPS receivers
provides combined performance, functionality, and integrity that
may not be available in either stand-alone SPS or PPS receivers.
For example, a PPS receiver may not provide as much functionality
(e.g., RTK, attitude information from multi-antenna systems, etc.)
or the level of performance provided by commercial survey, machine
control, or civil aviation SPS receiver. In addition, by
cross-validating the data of the SPS receiver with that of the PPS
receiver, the provision of anti-spoofing capabilities from the PPS
receiver may allow the use of the SPS receiver to operate in an
environment in which anti-spoofing functionality is a requirement.
For example, the increased level of integrity may be used to reduce
possible harm to human life if invalid GPS signals are used (e.g.,
civil aviation).
[0041] With reference now to step 301 of FIG. 3, a positioning
signal is received. In one embodiment, the positioning signal may
be comprised of P code, CA code, and/or Y code contained on an L1
band and/or an L2 band.
[0042] With reference now to step 303 of FIG. 3, in one embodiment
both receivers attempt to acquire. That is, both the PPS receiver
and the SPS receiver attempt to acquire the positioning signal. The
attempt to acquire may be from a cold start (e.g., no
initialization), a warm start (e.g., approx. 50% initialization),
or a hot start (e.g., approximately 95% initialization). In one
embodiment, the initialization of the receivers refers to position,
velocity, time, and data (PVT). The starting temperature (e.g.,
cold, warm, or hot) may be functions of how recently the receiver
has been used. For example, if the last use was in the same general
area and utilized the same visual cues (e.g., satellites) as the
present use, then the acquisition time may be much faster than for
a receiver that has not been utilized in the same area or within
the same time frame.
[0043] With reference now to step 305 of FIG. 3, after an amount of
time has passed since receiving the positioning signal, both the
SPS and the PPS receivers may or may not have successfully acquired
the positioning signal. In general, there are four possibilities.
Both the PPS receiver and the SPS receiver have acquired, the PPS
receiver has not acquired but the SPS receiver has, the PPS
receiver has acquired but the SPS receiver has not, or neither the
SPS receiver nor the PPS receiver have acquired the data in the
positioning signal.
[0044] Referring now to step 310 of FIG. 3, in one embodiment both
the PPS receiver and the SPS receiver have acquired the positioning
signal. In general, once a receiver has initially acquired the GPS
positioning signal, the receiver will perform a self-validation to
ensure that it is running correctly and that the GPS data allows
for proper operation.
[0045] With reference now to step 311 of FIG. 3, once they have
both successfully acquired, the receivers (e.g., SPS and PPS) then
cross-validate the data. That is, they compare their individual
databases to ensure that they are both receiving correlating data.
For example, the data may be compared at the level of the 1500 bit
navigation message (e.g., raw data). That is, the PPS and the SPS
receivers may compare their 1500 bit navigation messages from each
satellite (or other devices delivering the GPS, or GLONASS or WAAS
positioning signal) to ensure they are both receiving the same
data.
[0046] Referring now to step 312 of FIG. 3, in one embodiment the
SPS portion of data and PPS portion of data are compared for
agreement purposes. For example, they may be compared at the level
of the 1500 bit navigation message, or any other level described in
more detail herein. In one embodiment, the cross-validation of data
may occur constantly. In another embodiment, the cross-validation
of data may occur in a cyclic manner. For example, depending on the
need for timely integrity data, the PPS receiver could be cycled on
and off periodically to save power. In addition, the SPS receiver
may also incorporate logic to periodically wake up the PPS receiver
based on time, mode, or GPS signal tracking history (e.g.,
significant change in received positioning signal strength,
appearance of a satellite not previously tracked by the PPS
receiver as listed in the "track list", or the like).
[0047] With reference now to step 313 of FIG. 3, if the SPS and PPS
data and receivers are in agreement (e.g., cross-validation has
been successful), both receivers remain operational and the use of
PPS receiver for validation and SPS receiver for operational uses
has been performed. In this case, the user may utilize both the SPS
and the PPS in their valid states.
[0048] However, with reference now to step 315 of FIG. 3, in one
embodiment if there is a discrepancy found during the
cross-validation process, the default may be the PPS data being
flagged as more valid than the SPS data.
[0049] This default maybe due to the collection of the PPS data
occurring through a layered protection scheme. For example, the PPS
receiver incorporates the Y code tracking capability (which is
harder to spoof) through the military cryptography function.
Furthermore, the PPS receiver obtains the GPS navigation message
from the Y code tracking thereby authenticating its validity. The
PPS receiver may also employ over-determined PVT solutions,
receiver autonomous integrity monitoring (RAIM), and/or fault
detection and Exclusion (FDE) to identify GPS positioning signals
that are not consistent with other positioning signals being
tracked. In addition, the PPS receiver may employ early-to-prompt
acquisition and periodic re-search to identify multi-path and
repeaters. The PPS receiver may also provides the combined system
with the ability to compute autonomous GPS PVT in the presence of
higher jamming levels than the SPS receiver can handle by itself.
The PPS receiver may further provide a direct measurement of
ionospheric delay from the L1/L2 measurement capability that can be
used by the SPS receiver in its own processing, instead of using
the SPS iono model or other iono estimates determined solely from
SPS means. In addition, the integrity/search bin data allows the
SPS receiver to directly acquire the positioning signal without
searching or to narrow its search window, thereby reducing the
acquisition/reacquisition time. For example, the PPS receiver may
track through an intermittent jammer/interference source while the
SPS receiver looses track. The integrity/search bin data may also
speed up the integer ambiguity resolution time.
[0050] Therefore, the SPS data may held as suspect in its origin
and overwritten by the PPS data on the SPS receiver. The overwrite
may occur on a GPS device by GPS device basis or on a complete data
overwrite basis. For example, if a single GPS device is providing
an errant positioning signal to the SPS receiver, the PPS receiver
may inform the SPS receiver to ignore the errant positioning signal
and operate without the erroneous positioning signal. However, if
the SPS receiver cannot operate correctly with the data it is
receiving, then the complete navigation data from the PPS receiver
may be utilized by the SPS receiver. Thus, even though the SPS
receiver cannot obtain the navigation data on its own, the SPS
receiver will still maintain operational capabilities thereby
allowing a user to have complete access to the necessary software
and hardware.
[0051] In addition, if the data from the SPS receiver is shown as
being suspect, a further analysis of the SPS data may include a GPS
device by GPS device analysis to see which GPS device is
transmitting the suspect data. This analysis of suspect data may
result in the recognition of a "spoofing" GPS device or a
non-operational device which may be providing one or more false
1500 bit navigation messages to the SPS receiver.
[0052] In another embodiment, if the compared data (e.g., SPS data
and PPS data) is not the same then no position may be provided by
the SPS receiver until it has been updated by the cryptographically
confirmed PPS receiver. In yet another embodiment, if the compared
data (e.g., SPS data and PPS data) is not the same then an
indicator may be utilized to inform the user of the possibility of
incorrect data and that the PVT data may not be relied upon (e.g.,
suspect). For example, the warning may be a colored light (e.g.,
red-warning, green-good), a blinking light, a flashing display, or
the like which would gain the attention of the user utilizing the
SPS receiver.
[0053] With reference now to step 318 of FIG. 3, the invalidated
SPS receiver may force the user to consciously select the PVT data
as unreliable data with only limited capabilities. For example, a
position may be obtained but no tracking may occur. In one
embodiment, the use of consciously selecting unreliable data may be
necessary because PPS data may be more difficult to acquire than
SPS data. For example, PPS and SPS receivers are in a different
location and the PPS receiver is being blocked, or the PPS
cryptographic data is invalid, or the like.
[0054] However, if the PPS receiver is supplying information to the
SPS receiver due to a degradation of the SPS receiver reception,
then the transfer of data may be performed at a classified or
unclassified level. At the unclassified level, the raw data or
pseudo uncorrected range from the PPS receiver may be passed to the
SPS receiver without classification problems. At the classified
level, data that has passed through the cryptography of the PPS
receiver and is then passed to the SPS receiver may require the SPS
receiver to also be classified. For example, if the SPS receiver
receives classified data from the PPS receiver (e.g., due to the
inability of the SPS receiver to acquire a positioning signal, or a
correct positioning signal, or jamming, or the like) then the SPS
receiver must also be treated as a cryptographic device and must be
treated with the same level of security as the PPS receiver
delivering the classified data.
[0055] With reference again to step 305 of FIG. 3, if the PPS
receiver has acquired but the SPS receiver has not acquired then
step 330 occurs. In one embodiment, the lack of SPS receiver
positioning signal acquisition may be due to jamming, spoofing,
lack of power, or the like.
[0056] Referring now to step 332 of FIG. 3, once the PPS receiver
is operational and has self-validated, the PPS receiver may then
begin aiding the SPS receiver by feeding data to the SPS receiver.
This transfer of data from the PPS receiver may occur at any of the
plurality of subsystems of the SPS and PPS receivers as described
herein (e.g., FIG. 4). For example, the PPS receiver may provide
the SPS receiver with unclassified raw data or pseudo range
variables to help the SPS receiver operate.
[0057] For example, the PPS receiver may provide the SPS receiver
with classified (or unclassified) PVT data which may allow the SPS
receiver to be operational without actually acquiring the data for
itself. In yet another embodiment, the PPS receiver may provide the
SPS receiver with other classified or unclassified data which may
allow the SPS receiver to be operational while it continues trying
to acquire its own data.
[0058] In addition to delivering data to the SPS receiver, the PPS
receiver and/or SPS receiver may analyze the possible causes for
the inability of the SPS receiver to acquire. This analysis may
result in the identification of the spoofing or jamming device or
any other number of reasons why the SPS receiver may not be
acquiring. It may also provide the SPS receiver with the correct
places to look for the signal from the GPS device. For example, if
the PPS receiver has been in the location for an amount of time and
the SPS receiver is new to the area, the PPS receiver may be able
to provide the SPS receiver with a hot load (e.g., up-to-date
satellite locations and strengths) thereby enhancing the
acquisition speed of the SPS receiver. In the prior art, if an SPS
receiver could not acquire, the user would be without PVT results.
In addition, the actual reason for the inability of acquisition for
the SPS receiver may not be resolved and the user of the SPS
receiver would be without an operational receiver.
[0059] With reference now to step 335 of FIG. 3, a check is
performed to see if the SPS receiver has acquired. In one
embodiment, if the SPS receiver does acquire then, as described
herein (e.g., step 311), the PPS receiver and the SPS receiver
cross-validate to ensure the data that is being utilized is valid.
And the process continues as described from step 311 of
cross-validation.
[0060] However, as described herein (e.g., step 318), if the SPS
receiver does not acquire, the user may have the option of feeding
the information from the PPS receiver to the SPS receiver in order
to make the SPS receiver operational. Furthermore, as described
herein, the data fed from the PPS receiver to the SPS receiver may
be classified or unclassified. If the data being passed is
classified then the SPS receiver becomes classified, however, if
the data being passed is not classified, then the SPS receiver
remains unclassified. The resulting SPS and PPS receiver
collaboration may then skip the cross-validate step (e.g., 311) and
operate in an invalid state. Specifically, there is no way to
cross-validate the data if there is only one set of data. Although,
in one embodiment, if the PPS data is shown as a reliable data set
during the self validation process, the data may be treated as
valid by the SPS receiver due to the cryptography associated with
the PPS receiver.
[0061] With reference again to step 305 of FIG. 3, if the SPS
receiver has acquired but the PPS receiver has not acquired then
step 320 occurs. In one embodiment, this lack of PPS receiver
positioning signal acquisition may be due to jamming, spoofing,
lack of power, incorrect cryptographic material, or the like,
wherein the PPS receiver fails to acquire.
[0062] Referring now to step 322 of FIG. 3, in one embodiment, once
the SPS receiver is operational and has self-validated, the SPS
receiver may then begin aiding the PPS receiver by feeding data to
the PPS receiver. This transfer of data from the SPS receiver may
occur at any of the plurality of subsystems of the SPS and PPS
receivers as described herein (e.g., FIG. 4). For example, the SPS
receiver may provide the PPS receiver with raw data or pseudo range
variables to help the PPS receiver acquire.
[0063] In one embodiment, the SPS receiver may provide the PPS
receiver with PVT data which may allow the PPS receiver to be
operational without actually acquiring the data for itself. In yet
another embodiment, the SPS receiver may provide the PPS receiver
with other data which may allow the PPS receiver to be partially
operational while it continues trying to acquire its own data.
[0064] In addition to delivering the positioning signal data to the
PPS receiver, the SPS receiver and/or PPS receiver may analyze the
possible causes for the inability of the PPS receiver to acquire.
This analysis may result in the identification of the spoofing or
jamming device or any other number of reasons why the PPS receiver
may not be acquiring. It may also provide the PPS receiver with the
correct places to look for the satellites. For example, if the SPS
receiver has been in the location for an amount of time and the PPS
receiver is new to the area, the SPS receiver may be able to
provide the PPS receiver with a hot load (e.g., up-to-date
satellite locations and strengths) thereby enhancing the
acquisition speed of the PPS receiver. In the prior art, if a PPS
receiver could not acquire, the user would be without PVT results.
In addition, the actual reason for the inability of acquisition for
the PPS receiver may not be resolved.
[0065] Referring now to step 325 of FIG. 3, in one embodiment if
the PPS receiver does acquire then, as described herein (e.g., step
311), the PPS receiver and the SPS receiver cross-validate to
ensure the data that is being utilized is valid, and the process
continues as described from the step of cross validation 311.
[0066] However, if the PPS receiver does not acquire, the user may
have the option of feeding the information from the SPS receiver to
the PPS receiver in order to make the PPS receiver operational.
Furthermore, as described herein, the resulting collaboration of
the receivers may then skip the cross-validate step and operate in
an invalid state. Specifically, there is no way to cross-validate
the data if there is only one set of data. However, since the PPS
data is the more reliable data set during the cross-validation, the
data may be treated as suspect by both the SPS and PPS receivers
(e.g., operate in the invalid state 318).
[0067] With reference again to step 305 of FIG. 3, if both the SPS
receiver and the PPS receiver have not acquired then step 340
occurs. That is, both receivers continue trying to acquire the
data. This may go on in infinitum or until the receivers are turned
off. In another embodiment, a user may be able to put in spatial
information in order to aid the SPS and PPS receivers in acquiring.
For example, if a map is available, the user may put in
latitude/longitude values, grid coordinates, or the like, to help
the PPS or SPS receiver locate itself. In addition, a user may be
able to input information regarding a spoofing positioning signal,
bad positioning signal, GPS device to ignore, or the like, which
may further allow the SPS and/or PPS receivers to acquire. In
another embodiment, a third GPS device may be found which can
supply the necessary data to the SPS or PPS receivers in order to
help the SPS or PPS receivers acquire.
[0068] With reference now to FIG. 4, the levels of possible SPS and
PPS cooperative operation is shown in accordance with one
embodiment of the present invention. As described herein, the
interaction between the SPS and PPS receivers may be at a variety
of levels and occur for a variety of time durations. For example,
if the SPS receiver is unable to acquire but the PPS receiver has
acquired (e.g., step 330 of FIG. 3), then the PPS receiver 450 may
provide raw data 410 (e.g., the 1500 bit navigation message) to the
SPS receiver 405 via communications channel 490. The outputting of
raw data 410 from PPS receiver 450 may continue until one or both
receivers are turned off, or until the. SPS receiver 405 is able to
acquire its own raw data 410.
[0069] In the same manner, if SPS receiver 405 has acquired and PPS
receiver 450 has not (e.g., step 320 of FIG. 3), then the SPS
receiver 405 may provide raw data 410 (e.g., the 1500 bit
navigation message) to the PPS receiver 450 via communications
channel 440. As stated herein, the outputting of raw data 410 from
SPS receiver 405 may continue until one or both receivers are
turned off, or until the PPS receiver 450 is able to acquire its
own raw data 410. In one embodiment, communications channels 490
and 440 may be wired or wireless communications capabilities. For
example, communications channels 490 and 440 may be bluetooth,
Infrared, USB, standard cable, copper wire, speaker-microphone, or
the like which may be capable of passing a positioning signal from
one receiver to another.
[0070] Although in the example stated herein, the PPS receiver 450
and the SPS receiver 405 pass data at the raw data 410 level. Each
receiver may pass the data from the positioning signal at a variety
of levels. For example, the data may be passed from the SPS
receiver 405 at the pseudo range 415 level, the propagated data 420
level, or the receiver autonomous integrity monitor (RAIM) 425
level. In addition, the data may be passed from the PPS receiver
450 at the pseudo range 465 level, the propagated data 470 level,
or the receiver autonomous integrity monitor (RAIM) 475 level.
However, as stated herein, at different levels of the PPS receiver
450, the positioning signal data that is being passed may become
classified. If the data being passed from PPS receiver 450 is
classified (e.g., SA or CVAS) then the SPS receiver 405 will become
a classified receiver to the same level as the PPS data being
passed. This changing classification level is only in one direction
however, since no data initially processed by the SPS receiver 405
and passed to the PPS receiver 450 is classified.
[0071] With reference now to FIG. 5, a flow chart of the method for
SPS and PPS cooperative operation is shown in accordance with one
embodiment of the present invention.
[0072] With reference now to step 502 of FIG. 5, in one embodiment
a positioning signal is received. As stated herein, the positioning
signal may be from a satellite based device, or the signal may be
from a GPS device placed in line of sight (or GLONASS or WAAS). For
example, if an area has low or weak satellite coverage, an Earth
based positioning signal generator may be utilized to distribute
the previously described positioning signal. The Earth based
positioning signal generator may be a land or sea type device and
may be portable or stationary. As described herein, the positioning
signal may be broadcast on two frequencies, L1 at 1575.42 MHz and
L2 at 1227.60 MHz. Furthermore, the positioning signal may include
the CA code and/or the P code (as stated herein, when encrypted,
the P code becomes the Y code).
[0073] Referring now to step 504 of FIG. 5, a PPS data portion of
the positioning signal is acquired with the PPS receiver. As
described herein, the PPS receiver is capable of receiving the
positioning signal on both the L1 band and the L2 band. In
addition, the PPS receiver includes a KDP (key data processor)
adapted to receive a CV (crypto variable) from an external keying
device. In general, the KDP operable for generating Crypto Variable
Anti Spoofing (Cvas) and selective availability (SA) correction
information. That is, the PPS receiver having a correct CV is
capable of accessing the CA code, the P code, and the encrypted Y
code.
[0074] With reference now to step 506 of FIG. 5, an SPS data
portion of the positioning signal is acquired with the SPS
receiver. As described herein, the SPS receiver is capable of
receiving the positioning signal only on the L1 band. In addition,
the SPS receiver does not include a KDP (key data processor).
Therefore, the SPS receiver is not adapted to receive a CV (crypto
variable) from an external keying device. That is, the SPS receiver
is only capable of accessing the CA code not the P code or the
encrypted Y code.
[0075] Referring now to step 508 of FIG. 5, in one embodiment the
PPS receiver is communicatively coupled with the SPS receiver. As
stated herein, the communicatively coupling may be performed by
wired or wireless methods. For example, the wired method may
utilize a cable plugged into both the PPS receiver and the SPS
receiver. The wireless method may use bluetooth protocol, Infrared,
speaker-microphone, or any other wireless method available to one
skilled in the art of wireless communications. In addition, the
communicatively coupling of the SPS receiver with the PPS receiver
may be manually initiated or it may be automatically initiated. For
example, in one embodiment, once one receiver acquires the
positioning signal it may begin to communicatively couple with the
other receiver. In another embodiment, the receiver may await a
positioning signal from a user before it begins to try to
communicatively couple with another receiver.
[0076] With reference now to step 510 of FIG. 5, the PPS data
portion from the PPS receiver may be cross-validated with the SPS
data portion from the SPS receiver. By cross-validating the data
from the SPS and the PPS receivers, information may be provided
about the validity of the positioning signal. For example, as shown
in FIG. 4, the raw data 410 may be compared to ensure that both
receivers are receiving the same information. This type of
cross-validation may be necessary to ensure that the SPS receiver
is not being spoofed. For example, a non-friendly positioning
signal (e.g., spoofing signal, purposely-wrong signal, or
malfunctioning device signal) may be being broadcast by a GPS
device. This non-friendly positioning signal may be able to
correctly mimic the CA code to throw the accuracy of the SPS
receiver off. In a worse case, the non-friendly positioning signal
may completely stop the SPS receiver from acquiring its position at
all. However, a PPS receiver having a higher security
classification than the SPS receiver may be able to utilize its
cryptographic capabilities, better signal reception, and the P (or
Y)-code to correctly locate itself. Therefore, by cross-validating
the raw data 410 or the pseudo ranges 415 and 465 (or any of the
other data fields described herein) between the two receivers the
non-friendly positioning signal may be identified and ignored. In
addition, the receivers may signal a user or other users of the
non-friendly device and ensure that other receivers are not
confused by the non-friendly positioning signal.
[0077] In a similar case, if the Cryptographic information (e.g.,
CV) is incorrect or malfunctioning, by cross-validating with an SPS
receiver, it may be verified that the PPS receiver may be
incorrectly loaded with CV or that a GPS device may be incorrectly
processing P code.
[0078] In one embodiment, during the cross-validating of the PPS
data portion with the SPS data portion, the PPS data portion may be
selected as the correct data portion if the cross-validating does
not agree. This selection of the PPS data over the SPS data is due
to the cryptographic capabilities utilized during the formation of
the PPS data. In another embodiment, during the cross-validation
process, if there is disagreement, as shown in step 315 of FIG. 3,
the user may be informed of the incongruity of the data and may
select either the PPS receiver or the SPS receiver as having the
most correct data. In so doing, the user will then know that the
operation of either the SPS receiver or the PPS receiver is being
done in an invalid state.
[0079] Referring now to FIG. 6, a diagram of computer system 611 in
accordance with one embodiment of the present invention is shown in
greater detail. Within the discussions herein, it should be noted
that certain processes and steps are discussed that are realized,
in one embodiment, as a series of instructions (e.g., software
program) that reside within computer readable memory units of
system 611 and executed by processor 601 of system 611. When
executed, the instructions cause the computer system 611 to perform
specific functions and exhibit specific behavior as described.
[0080] In general, computer system 611 used by the present
invention comprises an address/data bus 600 for communicating
information, one or more central processors 601 coupled with the
bus 600 for processing information and instructions, a computer
readable volatile memory unit 602 (e.g., random access memory,
static RAM, dynamic, RAM, etc.) coupled with the bus 600 for
storing information and instructions for the central processor(s)
601, a computer readable non-volatile memory unit (e.g., read only
memory, programmable ROM, flash memory, EPROM, EEPROM, etc.)
coupled with the bus 600 for storing static information and
instructions for the processor(s) 601. System 611 also includes a
mass storage computer readable data storage device 604 such as a
magnetic or optical disk and disk drive coupled with the bus 600
for storing information and instructions. Optionally, system 611
can include a display device 605 coupled to the bus 600 for
displaying information to the computer user (e.g., maintenance
technician, etc.), an alphanumeric input device 606 including
alphanumeric and function keys coupled to the bus 600 for
communicating information and command selections to the central
processor(s) 601, a cursor control device 607 coupled to the bus
for communicating user input information and command selections to
the central processor(s) 601, and a signal generating device 608
coupled to the bus 600 for communicating command selections to the
processor(s) 601.
[0081] With reference now to FIG. 7A, a block diagram of a system
for SPS and PPS cooperative operation having a separate antennae
configuration is shown in accordance with one embodiment of the
present invention. System 700 includes an SPS receiver 405 for
processing the SPS data portion of the positioning signal and a PPS
receiver 450 for processing the PPS portion of a position signal.
In one embodiment, both the PPS receiver 450 and the SPS receiver
405 have a radio frequency (RF) down converter, a digital signal
processing (DSP) engine, and communications protocols and devices
(e.g., ports, timing, and the like). In addition, the PPS receiver
450 has the PPS engine which is utilized for the cryptographic
processes of the PPS receiver 450 as described in more detail
herein.
[0082] In one embodiment, the PPS and SPS receivers provide
combined performance, functionality, and integrity that may not be
available in either stand-alone SPS or PPS receivers. For example,
a PPS receiver may not provide as much functionality (e.g., RTK,
attitude information from multi-antenna systems, etc.) or the level
of performance provided by commercial survey, machine control, or
civil aviation SPS receiver. In addition, by cross-validating the
data of the SPS receiver with that of the PPS receiver, the
provision of anti-spoofing capabilities from the PPS receiver may
allow the use of the SPS receiver to operate in an environment in
which anti-spoofing functionality is a requirement. Furthermore, in
any of the embodiments, as described herein, the SPS receiver and
the PPS receiver may be constantly active, or one may
intermittently turn on to cross-validate with the other. For
example, if the functionality of the SPS receiver is the main
utilization, the PPS receiver may cycle on and off at a rate which
allows power saving capabilities for the PPS receiver while also
maintaining the integrity of the cross-validation of the SPS
position data (or vice-versa).
[0083] System 700 also includes ports 715 which may be wired ports
(e.g., serial ports, USB ports, or the like) or wireless ports
(e.g., infrared, infrasonic, bluetooth, laser, or the like). In
addition, in one embodiment, system 700 may also include a device
710 for communicatively coupling SPS receiver 405 with the PPS
receiver 450. For example, if the ports 715 are wired ports, device
710 may be a cable capable of transmitting data which may plug into
ports 715 thereby communicatively coupling the SPS receiver 405
with the PPS receiver 450. In one embodiment, in order to keep the
communicatively coupled SPS receiver 405 from becoming classified
when keyed with the PPS receiver 450, the Y-code derived carrier
phase information may retain the SA when it is passed from the PPS
receiver 450 to the SPS receiver 405. Therefore, the PPS receiver
450 would remain classified but the data passed, and thus the SPS
receiver 405 would remain unclassified. In another embodiment, the
PPS and SPS receivers may be bolted together and common data
interfaces such as RS-232 ports may be connected.
[0084] With reference still to FIG. 7A, due to the communicative
coupling of system 700, as long as the PPS receiver 450 is
processing position location, the operational capabilities of the
SPS receiver 405 may remain functional regardless of the
acquisition status of the SPS receiver 405. However, as described
herein, when the SPS receiver 405 does have position data, it may
be cross-validated with the PPS receiver 450 to ensure that
incorrect signals are not being received. In addition, due to the
passing of positioning data between the devices, if either the PPS
receiver 450 or the SPS receiver 405 are having trouble acquiring
the correct location, one of the receivers may provide data to any
other receivers (as described herein) to allow the acquisition
process to occur.
[0085] System 700 also includes antenna 730 which may be any type
of antenna capable of receiving the positioning signal from a
positioning signal device. For example, as described herein, the
positioning signal may be a GPS, GLONASS, WAAS, or the like.
Specifically, in system 700, each receiver (e.g., PPS 450 and SPS
405) has its own antenna 730. Therefore, system 700 is the simplest
embodiment for utilizing the combination of the SPS receiver 405
and the PPS receiver 450 as described herein. However, by utilizing
two antennae 730 instead of just one, a small error may be
introduced into the cross-validating that would need to be
accounted for. In addition, to ensure the highest accuracy, both
antennae's 730 should be kept within close proximity.
[0086] With reference now to FIG. 7B, a block diagram of a system
for SPS and PPS cooperative operation having a shared antenna
configuration is shown in accordance with another embodiment of the
present invention. Specifically, system 750 of FIG. 7B is similar
in function and appearance to that of system 700 of FIG. 7A.
However, system 750 utilizes a single antenna 730 for both the SPS
receiver 405 and the PPS receiver 450. For example, the positioning
signal from the antenna 730 is sent via communications device 760
(e.g., wired or wireless) to positioning signal ports 765 (also
wired or wireless). By utilizing a single antenna 730, the afore
mentioned error introduced by two antennae 730 is removed and a
simpler cross-validation may occur. In another embodiment, system
750 may utilize only one communications device (e.g., only 760 and
not 710) to complete the function of passing the initial
positioning signal to the SPS and PPS receivers as well as
providing the communications for cross-validation between the two
receivers. In yet another embodiment, system 750 may utilize a
single port (e.g., 765 or 715) per receiver to both receive the
positioning signal as well as providing the ability to
cross-validate between the receivers. In a further embodiment,
there may be any number of receivers communicatively coupled to
cross-validate the positioning data. In addition, the any number of
receivers (e.g., PPS or SPS) may all share, or only some share, an
antenna 730.
[0087] With reference now to FIG. 8A, a block diagram of a system
for SPS and PPS cooperative operation having a separate antennae
configuration and a controller is shown in accordance with one
embodiment of the present invention. System 800 includes an SPS
receiver 405 for processing the SPS data portion of the positioning
signal and a PPS receiver 450 for processing the PPS portion of a
position signal.
[0088] System 800 also includes ports 815 which may be wired ports
(e.g., serial ports, USB ports, or the like) or wireless ports
(e.g., infrared, infrasonic, bluetooth, laser, or the like). In
addition, in one embodiment, system 800 may also include a
controller 870 for communicatively coupling SPS receiver 405 with
the PPS receiver 450. For example, if the ports 815 are wired
ports, controller 870 may communicatively couple via a cable with
ports 815 thereby communicatively coupling the SPS receiver 405
with the PPS receiver 450. In one embodiment, the controller 870
utilizes the position data of the PPS receiver 450 in combination
with the functionality of the SPS receiver 405. Moreover, due to
the combination of the signals within controller 870, as long as
the PPS receiver 450 is processing position location, the
operational capabilities of the SPS receiver 405 will remain
functional regardless of the acquisition status of the SPS receiver
405. However, as described herein, when the SPS receiver 405 does
have position data, it will be cross-validated with the PPS
receiver 450 to ensure that incorrect signals are not being
received. In addition, due to the passing of positioning data to
the controller 870, if either the PPS receiver 450 or the SPS
receiver 405 is having trouble acquiring the correct location, the
controller 870 may provide data between the two or more receivers
to allow the acquisition process (as described herein) to
occur.
[0089] In order to keep the communicatively coupled SPS receiver
405 from becoming classified when keyed with the PPS receiver 450,
the Y-code derived carrier phase information may retain the SA when
it is passed from the PPS 450 to the SPS 405. Therefore, the PPS
receiver 450 would remain classified but the data passed, and thus
the SPS receiver 405 and controller 870 would remain
unclassified.
[0090] System 800 also includes antenna 730 which may be any type
of antenna capable of receiving the positioning signal from a
positioning signal device. For example, as described herein, the
positioning signal may be a GPS, GLONASS, WAAS, or the like.
Specifically, in system 800, each receiver (e.g., PPS 450 and SPS
405) has its own antenna 730. Therefore, system 800 is the simplest
embodiment for utilizing the combination of the SPS receiver 405
and the PPS receiver 450 with a controller 870 as described herein.
However, by utilizing two antennae 730 instead of just one, a small
error may be introduced into the cross-validating that would need
to be accounted for by controller 870. In addition, to ensure the
highest accuracy, both antennae's 730 should be kept within close
proximity.
[0091] With reference still to FIG. 8A, system 800 also includes a
display 605. As described herein, display 605 may be graphic user
interface (GUI) or any other type of display. For example, if the
system 800 is being utilized in a survey format, the SPS receiver
405 and PPS receiver 450 may be in locations which are not easily
accessible while the controller 870 and/or display 605 may be in an
easily accessible location. For example, if the system 800 is
located on a mechanical device (e.g., grater, tractor, forklift,
crane, or the like) the antennas 730 may be atop the highest point
to get the best reception, the SPS 405 and PPS 450 receivers and/or
controller 870 may be in a single command and control location, and
the display may be in the mechanical device being operated.
[0092] With reference now to FIG. 8B, a block diagram of a system
for SPS and PPS cooperative operation having a shared antenna
configuration and a controller is shown in accordance with another
embodiment of the present invention. Specifically, system 850 of
FIG. 8B is similar in function and appearance to that of system 800
of FIG. 8A. However, system 850 utilizes a single antenna 830 for
both the SPS receiver 405 and the PPS receiver 450. By utilizing a
single antenna 730, the afore mentioned error introduced by two
antennae 730 is removed and a simpler cross-validation may occur.
In another embodiment, system 850 may utilize a signal splitter 860
to complete the function of passing the initial positioning signal
to the SPS 405 and PPS 450 receivers. In yet another embodiment,
system 850 may utilize a single port (e.g., 865 or 815) per
receiver to both receive the positioning signal as well as
providing the ability to cross-validate between the receivers. In a
further embodiment, there may be any number of receivers
communicatively coupled to cross-validate the positioning data. In
addition, the any number of receivers (e.g., PPS or SPS) may all
share, or only some share, an antenna 730.
[0093] With reference now to FIG. 9, a block diagram of a system
for SPS and PPS cooperative operation having a shared antenna and a
standard form factor interface configuration is shown in accordance
with one embodiment of the present invention. Specifically, system
900 of FIG. 9 illustrates an example of a survey type configuration
of an SPS receiver 405 having both a survey receiver 910 and a data
collector 920. In one embodiment, the survey receiver 910 is
utilized to perform the survey program while the data collector 920
is utilized to provide the positioning signal data to be
incorporated with the survey program within the SPS receiver
405.
[0094] With reference still to FIG. 9, the PPS receiver 450 is a
standard form factor interface that removably couples with the data
collection portion 920 (e.g., slot 945) of the SPS receiver 405
thereby communicatively coupling the PPS receiver 450 and the SPS
receiver 405. Both the SPS receiver 405 and the PPS receiver 450
utilize a single antenna 730 for obtaining the positioning signal,
and the operational capabilities of the SPS receiver 405 may be
enhanced by the accuracy of the PPS receiver 450. In yet another
embodiment, a cross-validation (as described herein) may be
performed between the SPS receiver 405 and the PPS receiver 450.
The standard form factor interface may be a personal computer
memory card interface architecture (PCMCIA card), a compact PCI
card, a compact flash card, or the like. In another embodiment, the
PPS receiver 450 may be integrated into a separate device (e.g., a
data collector 920 separate from SPS receiver 405) that may then
transmit the data (e.g., wireless or wired) to the SPS receiver
405.
[0095] With reference now to FIG. 10, a block diagram of a system
for SPS and PPS cooperative operation having a survey configuration
is shown in accordance with one embodiment of the present
invention. System 1000 is another example of cooperative operation
of an SPS and PPS receiver, which may be utilized in a survey type
environment. For example, system 900 may include a pole 1040 and
the SPS receiver 405 and PPS receiver 450 may be located on the
pole a specific distance 1020 below the antenna 730. This type of
configuration is normally utilized in the survey field when the
antenna 730 needs to be able to receive a clear signal and the SPS
receiver 405 needs to be accessed by the user performing the
survey.
[0096] By combining the operational capabilities of the SPS
receiver 405 with the more precise (and less spoofed) PPS receiver
450, each of the embodiments described herein is more capable of
ensuring the integrity of the positioning network (e.g., GPS or the
like). For example, if a number of virtual reference stations (VRS)
are positioned throughout a territory (e.g., if the country has
poor satellite coverage, or the like) they may stream data back to
a network processing center which would know the initial locations
of each of the VRS devices. If even one the VRS devices is moved,
the position data which is being broadcast may become incorrect and
an SPS receiver with limited acquisition ability and no
cryptography may never recognize that an error is occurring.
However, a PPS receiver having better acquisition capabilities and
cryptography may be able to connect with the network or an SPS
receiver and cross-validate or invalidate the position data being
output by the SPS receiver. Thus, the integrity of the SPS receiver
is maintained due to the input from the PPS receiver.
[0097] Thus, the present invention provides a method for SPS and
PPS cooperative operation. Embodiments of the present invention
also provide a method for SPS and PPS cooperative operation which
allows the better applications of the civilian SPS receiver to
operate in the more accurate DOD environment of the PPS receiver.
Embodiments of the present invention further provide a method which
provides these advantages without compromising accuracy, integrity,
or security.
[0098] The foregoing descriptions of specific embodiments of the
present invention have been presented for purposes of illustration
and description. They are not intended to be exhaustive or to limit
the invention to the precise forms disclosed, and obviously many
modifications and variations are possible in light of the above
teaching. The embodiments were chosen and described in order best
to explain the principles of the invention and its practical
application, thereby to enable others skilled in the art best to
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated. It
is intended that the scope of the invention be defined by the
Claims appended hereto and their equivalents.
* * * * *