Our Skywarn group is looking for a way to feed the positions of our spotters (reported via APRS) to into GRLevel3 to be displayed on the map. Does anyone know of a tool for doing this, or documentation that might help us create our own data feed?
I'm going to assume for now that anyone using GRLevel3 is already relying on internet access, so they won't mind also relying on it for obtaining the APRS data. aprs.fi provides an API where you can query their data at "a reasonable rate": https://aprs.fi/page/api
GRLevel3 supports importing data from custom "placefiles", whose format is defined here: http://www.grlevelx.com/manuals/gis/files_places.htm . These can be local files or URLs. The placefile format includes a way to specify how often GRLevel3 should re-read the file.
So all that's needed is a program that queries aprs.fi and writes a local file in GRLevel3's placefile format. (If you know of such a program, please post an answer!)