It looks like this boils down to
- With GPS175 the position source is ARINC 429 stream which has a "low" 0.01 min resolution (110 and 111 labels) per the standard
- When SafeFly is the source the NMEA 0183 format is in use with a signficiantly more fine grained resolution
- GRT switches the position source according to the selected NAV source
This is in contrast with Dynon which has an independent setting for the position data. Dynon recommends to always set SV-GPS-2020 for position data even with the TSO gps as the NAV source. The dynon GPS also sends the position at 4Hz vs TSO gps which may send it only at 1Hz - this helps to have a smoother moving map animation.
may be it makes sense for GRT to implement a similar approach vs looking for the high res position data in the ARINC 429 feed..
