GPS - Iridium Used for GPS Augmentation

Author

Iridium Used for GPS Augmentation

Mike

2007-02-10, 3:33 pm

Hello:

I had seen a short reference to the idea of using the existing Iridium
satellite system to somehow augment GPS signals. Could anyone refer
me to a reference for this?

Thanks in advance,

Mike

Marc Brett

2007-02-10, 10:33 pm

On 10 Feb 2007 11:42:00 -0800, "Mike" <mstevens44@gmail.com> wrote:

>Hello:
>
>I had seen a short reference to the idea of using the existing Iridium
>satellite system to somehow augment GPS signals. Could anyone refer
>me to a reference for this?

Not augmentation per-se, but Iridium has been used as a communication channel
for real-time DGPS data from a world-wide network of ground stations to global
wanderers such as long-range aircraft. Eg.:

http://trs-new.jpl.nasa.gov/dspace/handle/2014/6357
http://trs-new.jpl.nasa.gov/dspace/...7/1/03-0165.pdf

http://trs-new.jpl.nasa.gov/dspace/...706?mode=simple
http://trs-new.jpl.nasa.gov/dspace/...6/1/03-1972.pdf

[Dig the cool picture of a P3-B masquerading as a DC-8 on page 3]

Iridium can make GPS signals jam-resistant:

http://www.google.com/patents?hl=en...id=USPAT7042392

GPS access system and method

"This invention describes a means for acquiring GPS P/Y code under jamming
conditions. It improves jam resistance by augmenting a component of the GPS
signal with one from a different satellite system, such as a low earth orbiting
(LEO) satellite. The preferred embodiment of this invention employs the Iridium
LEO satellite constellation broadcasting in a 10 MHz wide band about 1,621 MHz.
A low-cost, integrated Iridium receiver coupled to the GPS receiver employs a
single antenna that is capable of receiving both the GPS and Iridium signals
together."

Or you use Iridium's (or any LEO satellite's) signal to enhance your position:

http://www.google.com/patents?vid=USPAT5812961

Method and reciever using a low earth orbiting satellite signal to augment the
global positioning system

"A method and an apparatus using a low Earth orbiting (LEO) satellite signal to
augment the Global Positioning System (GPS) for finding a location vector
between a GPS user receiver and a GPS reference receiver. The GPS user receiver
computes a LEO user-reference carrier phase difference and a GPS user-reference
carrier phase difference for the LEO satellite signal and a GPS satellite
signal, respectively, received simultaneously at the GPS user receiver and the
GPS reference receiver. Carrier phase double differences are computed from a
difference between the GPS user-reference carrier phases from two GPS satellites
and either the LEO user-reference carrier phases from two LEO satellites or the
GPS user-reference carrier phase from one GPS satellite and the LEO
user-reference carrier phase from one LEO satellite. The location vector is
computed from a difference between the double differences for two satellite
geometries."

http://www.google.com/patents?vid=USPAT6373432

System using leo satellites for centimeter-level navigation

"Disclosed herein is a system for rapidly resolving position with
centimeter-level accuracy for a mobile or stationary receiver. This is achieved
by estimating a set of parameters that are related to the integer cycle
ambiguities which arise in tracking the carrier phase of satellite downlinks. In
the preferred embodiment, the technique involves a navigation receiver
simultaneously tracking transmissions from Low Earth Orbit Satellites (LEOS)
together with transmissions from GPS navigation satellites. The rapid change in
the line-of-sight vectors from the receiver to the LEO signal sources, due to
the orbital motion of the LEOS, enables the resolution with integrity of the
integer cycle ambiguities of the GPS signals as well as parameters related to
the integer cycle ambiguity on the LEOS signals. These parameters, once
identified, enable real-time centimeter-level positioning of the receiver "

Or use the high-power signal from Iridium to help track the low-power GPS signal
inside a building:

http://www.google.com/patents?hl=en...id=USPAT6178195

Method and apparatus for detecting spread spectrum signals using a signal from a
secondary source

"A method and apparatus for detecting and tracking spread spectrum signals, such
as Global Positioning System (GPS) signals, first obtain precision timing and
frequency reference information from a relatively high-power, secondary signal,
such as that emanating from a satellite of a low-earth orbit (LEO) satellite
communications system, and then use such reference information to perform
narrow-band detection of the GPS spread spectrum signal. Accordingly, spread
spectrum signals are more efficiently detected and tracked, particularly in
environments where they are attenuated by obstacles such as buildings or
environmental barriers."

You might use the Iridium signal to get accurate time, which speeds up the GPS
position solution:

http://www.google.com/patents?hl=en...id=USPAT5945944

Method and apparatus for determining time for GPS receivers

"A method and apparatus of determining the time for a global positioning system
receiver is disclosed. Timing signals derived from a communication system, such
as cellular phone transmission signals, are received by a GPS receiver and
decoded to provide accurate time information. The timing signals may be in the
form of synchronized events marked by timing indicators, or as system time
information. The timing signals in combination with satellite position signals
received by the GPS receiver are used to determine the position of the GPS
receiver."

http://www.google.com/patents?hl=en...id=USPAT6323804

Method and apparatus for GPS time determination

"A system for rapidly acquiring a time reference for the location determination
of a wireless communication device. The system includes a wireless communication
device (200), a GPS satellite (202) and a communication satellite (208). The
method comprises the steps of acquiring a communication satellite signal (210)
and using the finite frame time to establish a course time reference. Once the
course time reference is established, an absolute device time is determined by
the wireless communication device, which as a result is synchronized to the
absolute time of the communication satellite (208) to within ten milliseconds.
The absolute device time is then used to synchronize the GPS portion of the
wireless communication device with the GPS satellite system."

It's a start. HTH

Simon Slavin

2007-02-12, 10:33 pm

On 10/02/2007, Mike wrote in message
<1171136520.721057.230080@l53g2000cwa.googlegroups.com>:

> I had seen a short reference to the idea of using the existing Iridium
> satellite system to somehow augment GPS signals. Could anyone refer
> me to a reference for this?

Your ground station would have to be specially programmed to do this. It
would be possible to use any set of satellites intended for a phone system
to add location information. But unless the satellites were programmed to
help, it would hardly be worth the battery power.

Are you sure you're not confusing Iridium with the new European equivalent
to GPS ?

Simon.
--
http://www.hearsay.demon.co.uk

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