Thursday, December 08, 2005

Automated Vehicle Location in GTViewer using APRS

Years ago when the Global Positioning System (GPS) was just beginning to make its impact on GIS, I would opine that, “GPS was a solution in search of a problem.” Obviously, today GPS is the solution to many GIS and non-GIS problems and is used daily in hundreds of different applications. And since I consider myself a knowledgeable person in the GIS industry, I thought I already knew about all of them. But recently while making arrangements to create a sample dataset for a potential client, I was surprised to learn something new about the use of the Global Positioning System (GPS).

Apparently, there is widespread use of GPS within the amateur or ham radio community which includes businesses, utilities, and municipalities. My understanding is that ham radios can be a more reliable form of communications than other radio-based systems- especially under emergency conditions.

Briefly stated, vehicles with ham radios and certain GPS devices can transmit data such as their GPS coordinates, estimated speed, bearing, and more. This is accomplished through the Automatic Position Reporting System (APRS). APRS is a system developed by Bob Bruninga which uses amateur radio to transmit position reports, weather reports, and messages between users. This data are received and eventually collated and stored within a central database. This database is available and accessible through the internet. Vehicles transmitting this data are displayed as icons with their call signs next to them on web-based, interactive maps. If you are interested in APRS and want to know more about it, please visit .

If you are looking for a specific vehicle and you know its call sign, you can enter the call sign and the vehicle’s position will be automatically generated and displayed for you on a map on the web site. This intrigued me and I wondered if I could develop an application which would query the database, receive the data, and display the location and data on a map within GTViewer. The result was a small, customized .ocx application I wrote that works within the standard GTViewer product as an external application. Using the Data Monitor toolkit functionality within GTViewer was straightforward and a lot of fun.

The results of my application as you can see are simple but as you might imagine you could get carried away and practically create your own Automatic Vehicle Location system.

As these screenshots illustrate, you don’t necessarily need the power of GTVx to create customized and functional applications. Many of them could be designed simply as external applications using your own data and GTViewer right out of the box!

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