How to create a multi-unit tracking application

I am currently working on an application that will allow users to track any number of GPS enabled radios within a specified group. The key to this application is the proprietary GPWGT NMEA string which not only has GPS location info but also an identifier. These strings are typically transmitted from each radio in a group or polled by a central radio in a group. This string has the basic construct of

$GPWGT,<FixStatus>,DD.MMMMM,d,DDD.MMMMM,d,<Altitude>, <COURSES>,<SPEED>,<NameId>,<SCODE>,<GroupId>,<Status>,<ICON>,<Date>,<Time>*CC<CR><LF>

Where *CC is the "check sum" value and are carriage return and line feed respectively.

As you can see it is really as simple as parsing out the individual values or tokens from the NMEA string. The GPS microphones being used for this project come with USB drivers that create a vertual COMM port so you can use the .NET commport control to receive the strings. It then mearly requires a way to manage the different units. In our case we created a utility to add new units and store all their attributes in a central XML file. Within the application itself we store GPS MIC classes in a collection that can be accessed whenever one of these GPWGT strings is received. This allows us to plot points for these units with unique symbols and colours.

So you can see that programming to use these multi-unit GPS transceivers is not rocket science. It is quite easy to do and a usable application can be created in a fairly short period of time.