I have released a new version of GPS Speedreader that adds reading and writing a new "minimal" file format that uses the ".gpy" file extension. This is based on the discussions here and on Mike's (K888) Github site. The .gpy files are 80% smaller than .ubx files, and 60% smaller than .oao files, so file transfers will be a bit faster. Thanks to everyone who contributed to the discussion.
Another new feature in this version of Speedreader is support for .gpx files, and for calculating speeds even if no "doppler" speeds are present. That may be of interest to some watch users. Whenever possible, the use of .fit files is preferable, since many watch manufacturers do not include some important information in the .gpx files.
Downloads of GPS Speedreader are at
ecwindfest.org/GPS/GPSSpeedreader.htmlThe .gpy format specification is at
github.com/prichterich/compactgnss/issues/2, with example code in Java at
github.com/prichterich/compactgnssThe file format definition is released to the public domain, and the example code is released under the MIT license, which allows for any use, including commercial, as long as the typical "No warranties" clauses are included.