2d gps_fix_flags

hi , we are using sodaq sara aff board and testing the gps functionality. Based on sodaq universal tracker sketch we have notice that GPS_FIX_FLAGS is set to true very late(~40sec cold start) even fixtype is set to 2 or 3. As you can see in the log attach the GPS_FIX_FLAGS set to true with minimum number of satellites 6. is this a configuration issue? For our project a 2D fixtype is required. From u-blox documentation (https://www.u-blox.com/sites/default/files/products/documents/u-blox8-M8_ReceiverDescrProtSpec_(UBX-13003221)_Public.pdf#page=340&zoom=100,0,0) section 8.2 seems that the fixmode is auto 2D/3D so we assumed that the fix flag should be set when a 2D fixtype is set.

the condition that we use in the code is:
if (((NavPvt->flags & GPS_FIX_FLAGS) == GPS_FIX_FLAGS) && ((NavPvt->fixType == 2) || (NavPvt->fixType == 3) || (NavPvt->fixType == 4)))
is it possible to get position fix with minimum number of satellites 3?

Hi @niovi,

~40 seconds on a cold boot is very fast.
It takes ~30 sec to download the almanac data, then it have to calculate it’s position.

It is possible to get a fix with a minimum of 3 satellites, but the amount of satellites used depends on multiple factors. When you have a view to the clear sky you will most-likely use more satellites. Just a minimum of 3.

On the next GPS fix event it should be faster, keep in mind that every 4 hours the almanac data needs to be refreshed.

Best regards,

thank you for your response.
the test was performed with clear sky. The 40seconds delay refers to the time between fixetype was set to 02(2D fix) using 3 satellites until the GPS_FIX_FLAGS become 01(true) using 6 satellites. That means that we get a valid gps fix 40 seconds after the 2Dfix and with 6 satellites. Question is there a relevance to the signal quality and satellite number? is there any configuration for the GPS_FIX_FLAGS?