Applied Location Corporation

Wed, 21 Jan 2004 05:14:07 GMT

Valuable work in indoor and urban canyon signals http://plan.geomatics.ucalgary.ca/indoorlocation.html. Note that the MacGougan Thesis incorporates a valuable overview of GPS errors.

Wed, 21 Jan 2004 04:41:21 GMT

National Scientific's GPS links page http://www.nsclocators.com/contact/GPSLinks.htm

Wed, 21 Jan 2004 04:02:41 GMT

Sigtech Navigation's subATTO technology: "...for wireless location to be useful it must operate most of the time in typical environments where wireless communications are employed. These include inside houses, shopping malls, office blocks, multi-storey car parks and urban canyons." http://www.signav.com.au

GPS Receiver Algorithms & System for Weak Signal Operation, a paper by Rod Bryant, Stan Dougan and Eamonn Glennon, given at GPS 2001, describes this technology:

ABSTRACT: A key requirement for emergency call location (eg E911), for robust operation of location-based m-commerce systems and for telematics systems is that the location technology be able to operate in urban canyons and inside buildings. The primary problems associated with weak signal operation are as follows: • In conventional GPS receivers sampling at the correlator output typically occurs at a sampling interval of the order of 1ms. With weak signals, however, the signal to noise ratio of these samples is too low to support lock-in of a phaselocked or frequency-locked loop. • With weak signals the signal to noise ratio is too low to support the extraction of the 50BPS navigation message from the signal. Aiding data is therefore required from an external source. • Because the data cannot be extracted, it is not possible for the receiver to synchronize to the incoming bits, words or subframes. It is therefore not possible to construct pseudoranges without prior information. The paper describes Sigtec Navigation’s subATTO technology. This scheme is demonstrably practical with today’s technology and available communications bandwidths. It provides sensitivity down to –185dBW (19dBHz). This is 5dB below an attoWatt (10-18 Watts) and has been shown to provide reliable positioning inside buildings, multi-storey car parks and in urban canyons without any aiding aat all. Results are presented from trials of this system.

Wed, 21 Jan 2004 02:42:52 GMT

GPS-Galileo Interoperability Study in Canada: http://www.novatel.com/NewsReleases/20021105.html or same thing at http://www.findarticles.com/cf_0/m0EIN/2002_Nov_5/93971209/p1/article.jhtml

From the minutes of the 2003-05-22 meeting of the Alberta Chapter of ION, Dr Gerard Lachapelle spoke on GPS Performance Under Weak Signal Environments and Indoor. The outline, here, can also be seen on their site:

· Introduction, FCC Regulations for E911, Wireless Location + GPS + Communications

· Estimate 2 Million chipsets shipped per month in 2003

· 100's of millions of users by end of decade

· RF Propagation

· Discussed Indoor location problems, lower SNR, large errors, reflected signals

· HSGPS and AGPS methods of improving availability

· Long signal dwell form 5ms up to 120ms

· Longer coherent integration via bit prediction in combination with non-coherent signal accumulation

· AGPS - assisted GPS, cell net passes ephemeris, GPS time, approximate position.

· Benefits

· Improves sensitivity using long dwell of 20 to 500ms

· Signal measured to -185dBw

· Indoor positioning and improved TTFF

· Urban Canyon Testing

· Results using high performance receiver - sparse availability

· Sirf HS (high sensitivity) - good availability, heavily filtered causing problems in corners, across track error up to 100m.

· Sirf HS combined with muRata Gyro - better availability and accuracy, but poor GPS position still affects position accuracy.

· Indoor Test Barn

· Wood -asphalt roof attenuated GPS signal by 5 to 12dB. Good results demonstrated from Sirf HS in standalone and DGPS modes.

· Indoor Location - Residence

· Basement Garage - concrete roof tiles, wooden garage door. GPS signal attenuated by 20-25dB.

· Availability good, position to 10m RMS.

· U of C Simulation Capabilities

· Is it possible to use a simulator to reproduce an indoor signal environment?

· Studies at U of C are progressing to create models to simulate the indoor environment for standardized testing of receivers.

· Conclusions - best solution is combination of high sensitivity receivers and self-contained sensors.

· Closing remarks and audience questions

· Interested attendees were then given a tour of the Navigation Lab facilities and Antenna Range at CCIT

Mon, 19 Jan 2004 05:16:20 GMT

GPS tutorial goldmine: http://www.palowireless.com/gps/tutorials.asp

2 different approaches to foliage: http://www.gpstom.de/GPS/gar-wood.htm

nice GPS overview, but somewhat out-of-date http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html

Sat, 22 Feb 2003 16:34:43 GMT

The Modernization of GPS: Plans, New Capabilities and the Future Relationship to Galileo, Keith McDonald (Navtech) 2002 is a useful and accessible program update. Details scenarios re the next 12-18 years and the expected EU program (GNSS/Galileo).

The Global Positioning System: A Shared National Asset, NRC 1995

The Global Positioning System: Assessing National Policies, Rand 1995.

Amy Paige Snyder discusses a number of Pacific Rim issues, and has a useful reference section.

"Raw data freaks" spend time testing GPS receivers and antenna and building a body of vendor-independent insights and characterizations for the rest of us interested in applications of these technologies. I learned a lot from Sam Storm van Leeuwen’s site. He in turn recommends David Martindale (awaiting link), Sam Wormley (awaiting link), Peter Bennett and Karen Nakamura. Karen has many further references.

A High Anitjam GPS-Based Navigator by Gustafson, et al from ION Tech meeting in 2000.

The National Research Council has recommended that the development and operational use of GPS receivers with enhanced antijam (A/J) capability be accelerated.[3] The transmitted GPS signal may be attenuated by trees, buildings, etc., resulting in reduced signal/noise ratio, even without jamming. This loss of signal results in an increase in effective J/S level.

Current Global Positioning System (GPS)-based navigation system performance is marginal in high-interference environments in both civilian and military applications. This paper presents a new approach to solving these problems using a design that may be implemented at low cost in software in existing and future GPS receivers.

Wed, 29 Jan 2003 03:07:59 GMT

Finding a cell phone under 5 floors of concrete. Put your cell phone in your car. Park 4 or 5 floors down. Go somewhere else and ask your PC where your phone is. When you get to this site click E911 & E211 for some useful E911 resources; click "In Action" to select a cool 5 min video. This is exciting stuff -- and the guy running Global Locate is obviously having fun!

Also from Global Locate, a 2001 paper entitled: "Global Locate Indoor GPS Chipset & Services" by Frank van Diggelen (on ION members site).

ABSTRACT: Indoor GPS, or more precisely High-sensitivity GPS, is a combination of Assisted-GPS (A-GPS) and massive parallel correlation. This paper describes a worldwide reference network that provides assistance data for AGPS receivers, and a GPS chipset that uses a massively parallel architecture, along with the assistance data, to provide unprecedented GPS performance. Both the network and the GPS receiver demonstrate performance improvements of 10× or greater over previous state-of-the-art. The worldwide reference network predicts GPS orbits ten days into the future. The GPS receiver achieves time-to-first-fix of 100 milliseconds, when outdoors, and 2 to 5 seconds when indoors. The receiver can power up, acquire satellites, and get an accurate fix when in the closed trunk of a car, inside office buildings, deep urban canyons, parking garages, or shopping malls. The paper also describes the chipset architecture, and shows how it is unlike any previous GPS receiver. By having enough correlators to observe all possible code delays simultaneously, the receiver removes the old distinction between acquisition and tracking. This makes it possible to integrate weak signals for hundreds of milliseconds, and thus acquire signals hundreds of times weaker than a standard GPS receiver.

GPRS: How important a role? Although GPS is the key enabler of the Location revolution that is beginning to unfold, there are many ancillary and equally critical technologies that will make many applications possible. Companies like DigitalAngel are betting on GPRS as the telecomm component.

What it takes to filter out signal errors. Professor Stefano Panzieri and his colleagues, while studying robot navigation in a parking lot, show what kinds of errors you deal with while a robot is stationary. If you wanted to use GPS to steer a vehicle, you'd have a challange. But this article also reveals a lot about what you need to know to pinpoint a stationary vehicle within a couple of cm. The original source is: S. Panzieri, F. Pascucci, G. Ulivi, “An Outdoor Navigation System Using GPS and Inertial Platform,” IEEE/ASME Trans. on Mechatronics, vol. 7, n. 2, pp. 134-142, 2002, IEEE, USA.

GPS World - Great source site. I rely on this site for information about the entire spectrum of location technologies. Although GPSWorld covers space, ground and user segments, its coverage of space segment news is the strongest I have found. Good place to track (no pun) what is happening to funding and maintenance of GPS or other sister systems in Europe, Russia, Japan.

Very clever application of location to security, here.

[Dorothy] Denning is pioneering a new type of copyright protection, called geo-encryption. It's a big deal in the information security arena, earning her the moniker of "America's cyberwarrior" from Time magazine and stoking the imaginations of everyone from Hollywood movie executives seeking ways to scare off Napster copycats to hospital administrators looking for a safe way to transport patient data across the Internet without fear of privacy breaches.