U.S. patent application number 09/967325 was filed with the patent office on 2002-05-30 for distributed sensing apparatus and method of use therefor.
Invention is credited to Payton, David W..
Application Number | 20020063225 09/967325 |
Document ID | / |
Family ID | 22886179 |
Filed Date | 2002-05-30 |
United States Patent
Application |
20020063225 |
Kind Code |
A1 |
Payton, David W. |
May 30, 2002 |
Distributed sensing apparatus and method of use therefor
Abstract
An apparatus configured to obtain, process, and relay data to a
user in a coherent and useful manner. An active fiducial 200 is
equipped with an interface for receiving and transmitting data. The
fiducial may transmit its position using a satellite-based position
sensing device 204 such as a GPS. Active fiducials may also be
equipped with battery power pack regenerated with solar cells 206.
Similarly, the fiducials can be equipped with at least one video
camera 208 or other device having a focal plane array and a
computer software system, configured to recognize shapes. The
fiducials may also be equipped with inductive coils 210 or other
means for sensing metal containing compounds. The active fiducials
may be equipped with a gas chromatograph 212. The active fiducials
may use a variety of propulsion means including motor driven tracks
214, motor driven wheels 216, propellers, or other device or a
combination of devices.
Inventors: |
Payton, David W.; (Woodland
Hills, CA) |
Correspondence
Address: |
Tope-McKay & Associates
23852 Pacific Coast Highway #311
Malibu
CA
90265
US
|
Family ID: |
22886179 |
Appl. No.: |
09/967325 |
Filed: |
September 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60235599 |
Sep 27, 2000 |
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Current U.S.
Class: |
250/559.22 |
Current CPC
Class: |
G05D 1/0259 20130101;
G05D 1/0291 20130101; G05D 1/0278 20130101; G08C 17/02 20130101;
G05D 2201/0207 20130101; G05D 1/0246 20130101; G01D 21/00 20130101;
G01S 5/0009 20130101; G05D 2201/0209 20130101 |
Class at
Publication: |
250/559.22 |
International
Class: |
G01N 021/86 |
Goverment Interests
[0002] Portions of this invention was made or used in conjunction
with U.S. Government support from the Defense Advanced Research
Projects Agency, under Contract No. N66001-99-C-8514. The U.S.
Government may have certain rights in this invention.
Claims
1. An active fiducial apparatus comprising: at least one sensor, at
least one data processing element, and a user interface: wherein
the at least one sensor is configured to receive data and to
provide the data to a data processing element, the data processing
element processes the data, and if the data falls within predefined
parameters, the data processor conveys a signal.
2. An apparatus as set forth in claim 1, further comprising a user
interface, whereby a user may utilize the user interface to provide
instructions to the active fiducial via the data processor.
3. An apparatus as set forth in claim 1, further comprising an
inter-fiducial interface, whereby the fiducial may communicate data
to other active fiducials.
4. An apparatus as set forth in claim 1, further comprising a means
for propulsion.
5. An apparatus as set forth in claim 4, wherein the means for
facilitating propulsion includes at least one of the following: a.
a wheel; b. awing; c. a lighter than air reservoir; d. a propeller;
and e. an attachment means.
6. An apparatus as set forth in claim 1, wherein the plurality of
active fiducials communicate with the user either directly or by
using at least one other active fiducial as a repeater station.
7. An apparatus as set forth in claim 6, wherein the means of
communication includes at least one of the following: a.
conventional radio waves; b. frequencies within the electromagnetic
radiation spectrum that are visible; c. frequencies within the
electromagnetic radiation spectrum that are not visible; and d.
electromechanical radiation.
8. An apparatus as set forth in claim 1, wherein the active
fiducials have at least one of the following sensors: a. thermal
sensor; b. a metal sensing means; c. a gas analysis means; d. a
focal plane array sensitive to radiation substantially within the
visible region; and e. a focal plane array sensitive to radiation
substantially in the infrared region.
9. An apparatus as set forth in claim 8, wherein the at least one
sensor on the active fiducial is: i. static relative to the active
fiducial; and ii. dynamic relative to the active fiducial.
10. An apparatus as set forth in claim 1, wherein the active
fiducials are equipped with a satellite-based positioning system
and wherein the active fiducials can transmit their location using
the satellite-based positioning system.
11. An apparatus as set forth in claim 1, wherein the fiducial
interface at the active fiducials is configured to receive data
transmitted by electromagnetic radiation and wherein the data is
relayed to the user using one of the following: i. color-based
illumination; ii. alternating periods of varying frequencies of
electromagnetic radiation illumination; and iii. alternating
periods of electromagnetic radiation at specific frequencies.
12. An apparatus as set forth in claim 1, wherein the active
fiducial interface transmits unique messages in a plurality of
directions using a plurality of directional transmitters.
13. A method for gathering and displaying useful data from at least
one source comprising the following steps: i. instructing a
plurality of active fiducials, whereby the instructions direct the
plurality of active fiducials to a desired target; ii. dispersing
the active fiducials to facilitate the location of at least one
target based upon the provided instructions; iii. sampling
environmental elements, using at least one sensor, until a match
for the provided instructions is found; iv. transmitting sensor
data to at least one of the following: a. other active fiducials;
and b. a user; and v. displaying data to the user in a usable
manner.
14. A method for gathering and displaying useful data as set forth
in 13, wherein the active fiducials are configured to receive
instructions by way of at least one of the following: a.
conventional radio waves; b. frequencies within the electromagnetic
radiation spectrum that are visible; c. frequencies within the
electromagnetic radiation spectrum that are not visible; and d.
electromechanical radiation.
15. A method for gathering and displaying useful data as set forth
in 13, wherein the sensor is at least one of the following: a.
thermal sensor; b. a metal sensing means; c. a gas analysis sensing
means; d. a focal plane array sensitive to radiation substantially
within the visible region; and e. a focal plane array sensitive to
radiation substantially in the infrared region.
16. A method for gathering and displaying useful data as set forth
in 15, wherein the sensors associated with each active fiducial is:
i. static relative to the active fiducial; and ii. dynamic relative
to the active fiducial.
17. A method for gathering and displaying useful data as set forth
in 15, wherein the active fiducials are equipped with a
satellite-based positioning system and wherein the active fiducials
transmit their location utilizing data provided by the
satellite-based positioning system.
18. A method for gathering and displaying useful data as set forth
in 15, wherein the active fiducial interface is configured to
receive data in electromagnetic radiation form, and wherein the
data is relayed to the user using one of the following: i.
color-based illumination; ii. alternating periods of varying
frequencies electromagnetic radiation illumination; and iii.
alternating periods of electromagnetic radiation at specific
frequencies.
19. A method for gathering and displaying useful data as set forth
in 15, wherein the active fiducial interface transmits unique
messages in a plurality of correspondingly unique plurality of
directions using a plurality of directional transmitters.
20. An active fiducial comprising: a means for obtaining
information; a means for conveying information to a user; and an
implicit means for conveying apparatus location.
21. An active fiducial as set forth in claim 20 wherein the means
for obtaining information comprises at least one of the following:
i. an environmental sensor; ii. another active fiducials.
22. An apparatus as set forth in claim 20 wherein the means for
conveying information to a user includes: i. an omni-directional
electromagnetic radiation originating transmitter; ii. a
directional electromagnetic radiation originating transmitter; iii.
an omni-directional electromagnetic radiation reflective
re-transmitter; iv. an electromagnetic radiation reflective
directional re-transmitter; and v. an electromechanical radiation
originating transmitter.
23. An apparatus as set forth in claim 20, wherein the implicit
means for conveying apparatus location identification includes: i.
providing a direct line of site to the fiducial; and ii. providing
an encumbered line of site to the fiducial, such that the fiducial
is only be visible to observers having specialized equipment.
Description
PRIORITY CLAIM
[0001] This application claims the benefit of priority to
provisional application No. 60/235,599, filed in the United States
on Sep. 27, 2000, and titled "Distributed Display Composed of
Active Fiducials".
TECHNICAL FIELD
[0003] The present invention relates generally to an apparatus and
a method configured to provide a user with data collected from
multiple sources.
BACKGROUND OF THE INVENTION
[0004] Conventional approaches to displaying information from
multiple sensors require a map of the environment to which the
information pertains and data regarding the coordinates of each
sensor. Generally data from each sensor is obtained and compiled by
way of a user interface, and the data is then displayed relative to
a map in the possession of a user. The data may be superimposed
onto the map at locations corresponding to the position of each
sensor.
[0005] Drawbacks to these approaches include the requirement of a
coordinate system that allows a correspondence between features on
the map and features in the environment. Further, the position of
each sensor must be known relative to the map. Accordingly, the
position of each sensor is generally indexed within the coordinate
system so that the relative position of each sensor is known and,
thereby, the relevance of the data obtained by each particular
sensor can then be ascertained.
[0006] There are numerous instances where a user is either unable
to obtain a map of the environment, or is unable to obtain a map
that is accurate enough to facilitate the coordination of gathered
data with the map.
[0007] Therefore, it would be desirable to have a means for
obtaining data from the environment whereby the data could be
coordinated with the sites of data collection without the need for
a map.
SUMMARY OF THE INVENTION
[0008] The present invention overcomes the limitations of the prior
art by providing an apparatus and method for obtaining data from an
environment wherein the data are associated with the data
collection sites without the need for a map of the environment.
This present invention provides a means for providing
location-specific information to a user from a collection of
distributed data sensors. The sensors will herein be referred to as
"active fiducials", robots, and sensors.
[0009] One embodiment of the present invention provides a method
configured to provide, in a coherent and useful manner, at least
one user with data collected by a plurality of active fiducials.
According to this method, there is a first step that includes an
instructing step, whereby a user provides the plurality of active
fiducials instructions or sensor criteria in order to direct the
plurality of active fiducials to a desired target. The second step
is a searching step, whereby the plurality of active fiducials are
dispersed and seek a target based upon the instructions or sensor
criteria provided by the user. The third step is a detection step,
wherein at least one of the plurality of active fiducials locates a
target matching the provided instructions or meeting the provided
sensor criteria. The fourth step is a notification step, wherein
the sensor data is optionally transmitted from the inter-fiducial
interface to other active fiducials within the plurality of active
fiducials or directly to a user or both. The fifth step includes a
receiving and converting step, wherein data are received by a user
and, as necessary, are converted into a user discernable
format.
[0010] Another embodiment of the present invention provides a
plurality of active fiducials configured to identify and convey
useful data to at least one user utilizing the plurality of active
fiducials. This embodiment provides an apparatus for displaying
data detected via one or more active fiducials, wherein the one or
more active fiducials act independently and operate without
internal maps of the environment of interest. Based upon
instructions provided by a user, optionally through a user-fiducial
interface, each fiducial is capable utilizing its plurality of
sensors to collect relevant data regarding a selected target. The
relevant data might include the direction of the target relative to
the fiducial. This data is provided to a processor configured to
receive the data and relay the data to a user-fiducial interface,
where it is converted to a user-friendly format, such as a heads up
display or head worn display.
[0011] Another embodiment provides an apparatus for gathering and
transmitting data to a user, comprising: one or more active
fiducials, wherein each fiducial further comprises at least one
sensor configured to collect data and provide that data to a
processor; a processor configured to receive the collected data and
relay it to an inter-fiducial interface and a user-fiducial
interface; an inter-fiducial interface configured to allow
communication between the active fiducials; and, a user-fiducial
interface configured to allow communication between the active
fiducials and the user.
[0012] In yet another embodiment the sensor on the active fiducial
is a camera which can be dynamically rotated on the active
fiducial, thus facilitating a plurality of environmental views
without requiring the active fiducial to move. One such embodiment,
envisions a camera mounted on a turret.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The accompanying drawings form a part of the specification,
and illustrate various embodiments of the invention. The drawings,
taken together with the description, serve to explain the
principles of the invention.
[0014] FIG. 1 is a flowchart depicting a method whereby a user
first instructs the active fiducials to locate a target based upon
criteria provided by the user;
[0015] FIG. 2 is a depiction of one embodiment of an active
fiducial according to the present invention;
[0016] FIG. 3 is an illustration of a plurality of active fiducials
in operation;
[0017] FIG. 4 is a diagram of an active fiducial unit relaying data
to a user by way of a user-fiducial interface; and
[0018] FIG. 5 is a split view of a plurality of active fiducials,
indicating an unaided view and an augmented view in the case where
a target is not discernable to a user.
DETAILED DESCRIPTION
[0019] The following description, taken in conjunction with the
referenced drawings, is presented to enable one of ordinary skill
in the art to make and use the invention and to incorporate it in
the context of particular applications. Various modifications, as
well as a variety of uses in different applications, will be
readily apparent to those skilled in the art, and the general
principles defined herein may be applied to a wide range of
embodiments. Thus, the present invention is not intended to be
limited to the embodiments presented, but is to be accorded the
widest scope consistent with the principles and novel features
disclosed herein. Furthermore it should be noted that, unless
explicitly stated otherwise, the figures included herein are
illustrated diagrammatically and without any specific scale, as
they are provided as qualitative illustrations of the concept of
the present invention.
[0020] The present invention provides a method and apparatus
whereby one or more active fiducials locate and gather data that is
then provided to a user. More specifically, the present invention
described herein contemplates numerous configurations in order to
accomplish the tasks of locating and obtaining relevant information
about a target based upon instructions provided to one or more
active fiducials by a user.
[0021] The flowchart shown in FIG. 1 outlines one embodiment of the
present invention, whereby data regarding a target is obtained,
processed, and relayed to a user in a coherent and useful manner.
According to this embodiment, there is at least one user and a
plurality of active fiducials. Accordingly, there is an instructing
step 100, whereby a user provides the plurality of active fiducials
with instructions or sensor criteria in order to direct the
plurality of active fiducials to a desired target. These
instructions may be permanently fixed, or may be varied either by
an end user or an intermediate user. Where an end user refers to a
final user and an intermediate user may refer to an entity that
either retransmits data, or uses collected data as a means to draw
conclusions, or make decisions, before the data is routed to the
end user. For example, the fiducials may be employed to help detect
incipient forest fires. In this case the fiducials sensors would be
programmed to seek out certain heat sources. Upon finding such a
heat source the discovering fiducial will relay a message to the
user, either through other intermediate fiducials or directly to an
end user, such as a forest ranger. The fiducial may transmit its
position using a satellite based position-sensing device such as
GPS, or by providing its direction to either other fiducials or
directly to the user. Thus if a plurality of active fiducials were
released into a forest they may be permitted to wander about
indefinitely, possibly using a solar power pack, in search of
forest fires. Similarly, the fiducials could be configured to look
for certain shapes, using commonly available video cameras and
shape identification software. Thus the fiducials may find
application in crime scene investigations, by searching fields or
buildings for instruments of the crime. The fiducials could also
search for metal containing compounds, such as weapons or land
mines, or even toxic substances. A simple gas chromatograph could
draw air and water samples and test for the presence of certain
chemicals in situ. According to the method of this embodiment, a
searching step 102 is performed next, whereby the plurality of
active fiducials are dispersed in order to seek a target based upon
the instructions or sensor criteria provided by the user. The third
step 104 is a detecting step, wherein at least one of the plurality
of active fiducials locates a target matching the provided
instructions or meeting the provided sensor criteria. The fourth
step 106 is a notifying step, wherein the sensor data is optionally
transmitted from the inter-fiducial interface to other active
fiducials within the plurality of active fiducials or directly to a
user, or both. The fifth step 108 includes a receiving and
converting step, wherein data are received by a user and, as
necessary, are converted into a user discemable format. In the
present embodiment, the data relayed by the active fiducials may be
sent to other active fiducials to optimize or modify their searches
and/or data acquisition.
[0022] Another embodiment of the present invention provides an
apparatus configured to obtain, process, and relay data to a user
in a coherent and useful manner. According to this embodiment, as
depicted in FIG. 2, each active fiducial 200 is equipped with an
interface for receiving data and transmitting data. Where data is
understood to include instructions, sensor criteria, sensor
reports, and other transceived data. Instructions may relate to the
dispersion pattern that the robots are to take, sensor criteria
would include both what to look for, and ideally at what level.
Thus, travel due north and report when the ambient concentration of
oxygen goes 12 percent. The sensor reports might include a report
stating that the ambient concentration of oxygen is 7 percent, and
include the fiducial's coordinates. This data interface may include
a remote receiving module 202 or another type of interface.
Instructions and sensor criteria can be permanently programmed into
the active fiducials, or may be varied either by the end user or an
intermediate user. For example, the fiducials may be employed to
help detect incipient forest fires. In this case the fiducials
sensors would be programmed to seek out certain heat sources. Upon
finding such a heat source the discovering fiducial will relay a
message to the user, either through other fiducials or directly to
the user. The fiducial may transmit its position using a
satellite-based position sensing device, or by providing its
direction to either other fiducials or directly to the user. In the
case where directions are provided using a satellite based position
sensing device the active fiducial will be equipped with a GPS
receiver 204 or equivalent system. Similarly if a radio beacon
system is utilized in place of a GPS, the fiducial would need to be
equipped with the appropriate technology. The active fiducials may
also be equipped with battery power pack regenerated with solar
cells 206. Similarly, the fiducials can be equipped with at least
one video camera 208 and a computer software system, configured to
recognize shapes, in all cases the active fiducial is defined to
include a data processor. The fiducials may also be equipped with
inductive coils 210 or other means for sensing metal containing
compounds. Additionally the fiducial may be equipped with a gas
chromatograph 212, configured to sample air or water and test for
the presence of certain chemicals in situ. Sensors need not be
statically mounted to the active fiducials. It is anticipated, and
in some cases preferred, that the sensors can change position on
the active fiducials. The video camera 208 could be mounted on a
turret to allow for a wide view range. The active fiducial is
intended to accommodate virtually any sensor or array of sensors.
Further, the active fiducials may use a variety of propulsion means
including motor driven tracks 214, motor driven wheels 216,
propellers, lighter than air reservoirs, such as hot air balloons
of dirigibles, or other propulsion device or a combination of
devices. The propulsion device will generally be coupled to a
steering mechanism, which, may be controlled, by user input, a
"smart" algorithm or similar artificial intelligence protocol, or
pre-specified directions such as a compass/GPS heading or by a
trial and error random walk, wherein the active fiducials travel
until their progress is sufficiently inhibited and then retreat.
The active fiducial often will simply be a sensor allowed to
statically remain in place, or move when acted upon by
environmental forces. In such a situation the fiducial would not
have any propulsion means. The active fiducials communicate with
the user either directly or through at least one other active
fiducial. The means of communication may either be by conventional
radio waves, or other bands within the electromagnetic radiation
range, visible or not. Additionally the active fiducial may use
electromechanical radiation, either alone or in conjunction with
electromagnetic radiation. The active fiducials may also be
attached to mobile objects such as motorized vehicles, planes or
animals. Such an embodiment may be equipped with adhesive, a cord
or wire or a magnetic adhesion device or other adhering device. In
this way the active fiducials could be readily affixed to a
plurality of mobile objects.
[0023] In another embodiment of the present invention, the active
fiducial is configured to provide visually discernable status
indicia. For instance, FIG. 3 presents a plurality of active
fiducials 300 that have found an object 302 matching a specified
criterion. In this case the each active fiducial is equipped with
an arrow 304 and a direction-specific transceiver 306 (see
outtake). Here, an active fiducial 300 has located a target 302, a
gun in this case, and has transmitted its findings to surrounding
active fiducials 300. Because a direction-specific transceiver 306
is utilized, each active fiducial receives information that is
appropriate to its position. In this embodiment the
direction-specific transceiver 306 comprises a plurality of light
emitting diodes 308, surrounded by a plurality of baffles. Each
diode emits at a unique wavelength or flash pattern, and directly
below or above each diode could optionally be an electromagnetic
radiation sensor for directional sensing. In this embodiment there
are 32 different wavelengths, or transmission patterns, thus
providing an angular resolution of about 10 degrees. There could be
greater or fewer wavelengths and the device could be interpreted
using only the unaided eye, for example through the use of colors.
In this embodiment of the present invention the user cannot see the
target, such a situation exists where there is no unobstructed
view, or where the subject matter is invisible, as is the case with
certain types of gas, heat, or otherwise difficult to discern
systems. In the present case the arrows point the user in the
direction of the target, even when the target is out of sight.
There is nothing exclusive about the use of arrows as indicia of
direction, directional color or other characteristics could be used
with comparable results. Consider the situation where red, green
and yellow diodes are used to indicate a fact concerning a region.
A green light could mean no hazard, a yellow light could indicate
the presence a toxin above a first threshold, and a red light could
indicate the presence of a toxin above a second threshold.
Alternatively, the data from the fiducials can be represented as an
overlay, the aggregation of the data from all the fiducials would
result in a coherent distributed display of information. This
display is comparable to a traditional display that is composed of
a plurality of pixels, each of which is insufficient to convey the
content of an image, but when taken in the aggregate form a useful
image. An example of such an application would be the placement of
active fiducials in the vicinity of a toxic chemical discharge. The
fiducials could use pseudo-color to dynamically map toxin
concentration gradients across a geographical area. Similarly,
temperature or any other environmental quality could be
measured.
[0024] In an alternative embodiment the light emitting diodes are
distinguishable based on a number of factors such as intensity, or
if the light emitting diode is made to have periods of alternating
of illumination. In such a scenario the periodicity of illumination
may be used to provide directional and substantive data. Further it
is anticipated that fairly complex patterns of periodicity and
varying wavelength could allow for a virtually limitless number of
unique directional signals. Alternative systems could use
directional radio transmitters, or directional acoustical
transmitters. Additionally, laser beams could be used to provide
better directional resolution. In such a case it is anticipated
that the intermittency of the transmitted beam would contain, at
least a portion of the coded directional component. In some
situations each active fiducial within an area may be able to
simultaneously provide unique localized information. Such a
situation exists where toxic gases are known to exist. By placing
active fiducials strategically across an area, a user could view
the toxic gas concentration gradients across the area. A
pseudo-color scheme could be used to depict concentration in a
heads-up display or other display. Similarly, various colored light
emitting diodes could be employed across the field, where the light
emitting diode's color could indicate concentration.
[0025] A diagram of a fiducial unit relaying data to a user by way
of a user-fiducial interface is shown in FIG. 4. In the present
embodiment of the invention, the user is holding or is wearing a
receiving unit 400, which is capable of receiving and interpreting
the data from an active fiducial 402. The converted data is put
into a form recognizable by a user and provided to a user. In this
case the data is displayed on a pair of glasses 404 which are
substantially transparent except for the selective placement of
fiducial related data. For the purposes of this application this
will be considered a heads up display. The relevant information can
be relayed to the user in numerous other ways such as a video
display or monitor or audio signal having a variable intensity or
tone.
[0026] In another embodiment of the present invention, the
transceiver transmits using electromagnetic radiation outside the
visible region, such as radio frequency, infrared light, microwave,
etc. The user then utilizes a receiver to decode the signals and
displays the directional data or other data. The data may be in the
form of an overlay on a heads up display, an augmentation of a
video feed, a display on a screen, such as a laptop, CRT, other
display, or other mode of data conveyance. Such an embodiment is
provided in FIG. 5. The non-augmented view 500 in this embodiment
shows only the active fiducials 502 in a specific location.
However, with the aid of an augmented view 504, the user further
sees the desired additional data regarding the position of the
target 506.
[0027] Yet another embodiment provides an active fiducial
comprising a means for obtaining information. In this embodiment
the means may be either a receiver, configured to collect data from
one or more other active fiducials, or it may be a sensor as
discussed earlier. If a sensor is used the sensor is configured to
not onluy collect data, but to provide the data to a sensor
interface, so that the collected data may be made available to a
user, either directly or through another active fiducial. According
to this embodiment there is also a means for conveying information
to a user, this means could include any means of data conveyance,
including the use of reflected light. Thus, the active fiducial may
display a non-illuminated sign, or an illuminated sign or any other
data conveyance means. Further, this embodiment envisions an
implicit means for conveying apparatus location identification. The
most obvious example is an active fiducial in plain sight. This
means of location providing information relies on the ability of
the user to ascertain the location of the active fiducial based on
the perception of the user. In more complex systems the active
fiducial may be concealed to the naked eye but visible with the aid
of an optical device. Thus, the user will extract an essential
element of information by visually perceiving the active fiducials,
even if the perception is accomplished with the aid of a user
operated device.
[0028] It is anticipated that the active fiducial will rely on at
least one means for conveying a signal. A non-exhaustive list might
include an omni-directional electromagnetic radiation originating
transmitter. Such a transmitter would include a transmitter
configured to transmit in virtually any spectrum of the
electromagnetic radiation region. Thus a light transmission and a
radio transmission would be anticipated. In this case the active
fiducial would actually power the transmitter. In another version
the active fiducial may use ambient energy to transmit a signal. An
example would be the situation where sunlight is allowed to impinge
on an object, and be reflected to a user. The reflected light would
provide a signal to the user. An pointing arrow or other data
indicia would be included in this embodiment. The electromagnetic
radiation emanating form the active fiducial, either originating or
being reflected, can be either visible from only one general
direction or visible form a plurality of directions. Additionally
the active fiducial may utilize audio signals either within or out
of the range perceptible by humans.
* * * * *