Excerpts from RLA's Newsletter
GLONASS WITHOUT RUBLES
The Glonass GPS system was designed to consist of 24 satellites the same as the US NavStar constellation. Glonass was declared operational in January, 1996. The theory of combining the US and Russian systems for superior GPS data collection is good.
But in actual performance, Glonass has fallen short. No more than 11-15 SVs have been operational or healthy at any one time. For example, near the end of January, 1999, 24 US SVs were operational but only 16 Glonass with 5 being designated as unhealthy, leaving 11 operational.
In addition, inaccurate range measurements pop-up without user warning.. The range inaccuracies can produce errors from 100 meters up to 24,000 meters! The Russians do not have the resources to maintain the Glonass GPS system.
Since information on the Russian system has been hard to come by and plagued with failed satellites, outages or incorrect or missing data, the US Federal Aviation Administration has slowed the process of setting technical standards.
US acknowledgement of parity with NavStar does not seem to be on the horizon.
Glonass means: Global'naya Navigationnaya Sputnikovaya Sistema.
WHERE IS GIS HEADED? At a recent ERSI national sales conference, these GIS technology trends were reported: -A shift from Unix to Windows NT These trends explain the sudden surge in GIS use. Gone are costly workstations and complicated GIS software. Now with a Pentium Pro, ArcView and GPS for data collection, everyone can be in the GIS hunt without going broke or crazy. GIS is no longer the domain of large organizations. Now a small city, consultant or government agency can be effective in GIS at a minimum pain and cost.
-Expensive hardware to cheap hardware
-Difficult to use to easy to use
-A shift in emphasis from data building to data use
-GIS centered to information centered
-Proprietary languages to standard languages.
-Integrated applications to component applications.
-Hybrid data types to relational models
-Local access to Internet delivery
At a recent ERSI national sales conference, these GIS technology trends were reported:
-A shift from Unix to Windows NT
These trends explain the sudden surge in GIS use. Gone are costly workstations and complicated GIS software. Now with a Pentium Pro, ArcView and GPS for data collection, everyone can be in the GIS hunt without going broke or crazy. GIS is no longer the domain of large organizations. Now a small city, consultant or government agency can be effective in GIS at a minimum pain and cost.
Y2K and GPS ROLLBACKS. WILL THE WORLD COME TO A HALT?
The Y2K problem is caused by the programming practice of shortened four-digit years into two digits, hence 1998 is stored as "98". Comes the millenium is the year 1900 or 2000? Data might be interpreted in either the 20th or 21st century. As a result, an estimated 1.5 billion lines of code must be date corrected
This could have a major impact on financial transactions or any time sensitive data. In many organizations, programming to correct for Y2K began a long time ago. Now they are finding the "corrections' themselves are subject to errors and lines of code may have been missed.
GPS has the added factor of a GPS week rollover. Precisely 13 seconds before midnight on Saturday, August 21, 1999, the GPS week 1023 ends and the GPS week rolls back to 0. Fortunately, the GPS rollback is much simpler to solve than its Y2K cousin.
Trimble's Web page gives a detailed explanation and hardware/software status as it relates to the rollback issues (http://www.trimble.com),
Want to test your own compute? Download YMARK2000 from the National Software Testing Labs http://www.nstl.com. May the millenium be with you!
AVL- HOW AUTOMATIC VEHICLE TRACKING WORKS
A major growth application for GPS systems is Automatic Vehicle Tracking (AVL). The AVL objective is to provide up-to-date location information for emergency vehicles, delivery trucks,
freight trucks, service vehicles etc.
The components of a GPS-based AVL system are a GPS unit on the truck or vehicle, a communications link between the vehicle and the base tracking system. The communication system is usually a conventional radio network already in place. A recent trend is to substitute a car cellular phone link. Cellular is becoming more economically feasible with the trend to charge by digital data packets rather than per call.
Some GPS vehicle-based sensors may have a dead reckoning setup to track the vehicle should a signal be blocked in an urban canyon. This consists of a flux-gate compass and input from the vehicle’s odometer. Once the signal is regained the GPS tracking kicks back in.
We are looking at several low cost AVL systems including Trimble’s. EMail us if you have an interest in evaluating an AVL system for your organization.
FACTS TO NOTE
Inexpensive Beacon Receiver for GeoExplorer.
We are preparing to offer a low cost Beacon receiver for GeoExplorers. Let us know if your are interested. When the unit is available, we will contact you.
What you can't see can hurt you.
Don't assume all GPS receivers are the same. The design and operation of the internal chips can make a major difference in accuracy and satellite tracking.
Trimble designs and produces chips with advanced manufacturing technology. As a result, the ICs are quieter and allow for superior tracking and data collections due to better signal to noise ratios (SNR).
GPS Hits Iraq
The latest Cruise missiles to hit Iraq were equipped with GPS/Inertial navigation. The GPS guidance system is used to get near the target. Next it switches over to optical and compares what it sees with a programmed target image. The missile follows the image until it detonates dead center.