I'm a recent user to Skydemon. It has worked perfectly for navigation with my old GPS receiver, an Emtac BTGPS III. No issues at all.

However, I've recently upgraded to a new receiver (here: http://www.gns-gmbh.com/index.php?id=79&L=1). It offers some benefits as it has a faster refresh, support for more constellations than just GPS, and SBAS. And also has a longer battery life.

The new receiver works flawlessly with Memory Map both on my PDA and my laptop, as well as with my Android phone. However, Skydemon will not work with it. When entering Navigation mode, it simply says "Seeking Satellites, 'n' found ('x' out there)". It never gets past that and never gets a fix, even though it often 'finds' as many as 15 or 16 satellites.

Feel free to upload a log of sentence output from your receiver here and I'll step through it to see why SkyDemon is having a problem with it.

You're absolutely right that SkyDemon ignores non GP sentences, as the vast majority of apps will. It should NOT be necessary for individual apps to process GLONASS or SBAS messages in order to gain the benefit from them. Any increased accuracy can and should be incorporated into the standard GP messages. We would only implement specific handling for extra messages to report extra information which isn't directly useful to GPS navigation.

Also, bear in mind that on iOS and Android we never even see the original GPS sentences. Both platforms offer a location services abstraction which detach location and navigation information from the underlying sentence stream.