Okay, so what did I find out. Neither GPX nor KML has a circle in their schemas. (GPX is really only good for points and lines). But I can use a polygon with KML. However, I need to update the polygon with real-time information. This poses an issue because polygons in GPX and KML don't really have an ID field to do an update. At this point i can only hope that when locus reloads a file with the same path, it removes the old file data, then adds the new file data.
KML does have a way to update the entire KML (or a region of the KML for performance), using the <Update> tag under <NetworkLinkControl>. This is probably an advanced feature that I doubt you have implemented in Locus, nor do I expect you to, since it's pretty complicated.
https://developers.google.com/kml/docum ... nce#updateBoth these methods lack the capability to shade the area in locus, which is another "nice to have"
What if i run a WMS server? I have much experience with WMS. Does locus pro only do WMS raster, or does it handle vector?