GPSrChive Discussion Forum

Hi.
With GPSMAP 66st, firmware 9.90 and GPS software 2.90. (No EPO-file).
Depending on satellite constellation, sometimes when GPS satellites are not well avaialble, I observed the following.

GLONASS 4 satellites locked with good reception.
GPS 2 satellites locked with poorer reception.
At this point the location was not found/calculated, even as these in total 6 satellites where available and remained for many minutes.

As soon as the unit found 2 more GPS-satellites the unit calculated the location.

I have observed this earlier as well for shorter period of time, but this time it was clear over a longer period of time (minutes), it seems the unit does not want to calculate the location unless a good enough amount of GPS satellites are found, no matter GLONASS (or GALILEO).

Has anyone else observed this or can explain what's going on?

Where on Earth can see four GLONASS satellites and only two GPS satellites?

Hi, it's not so much about where it can happen (it happened in sweden, around 60 degrees north).
It simply happens that the unit finds many GLONASS satellites before many GPS satellites (GALILEO is usually always slower to lock than GPS).

The main question is still:
When it happens, why doesn't the unit calculate the position with help of the data from 4 GLONASS + 2 GPS satellites?
it should be enough i imagine.

Is this easy to reproduce?

Can you take some screen captures showing few GPS SV and multiple GLONASS SV with no calculated position?

I may have to ask a Garmin engineer, but not without some data to present.

Hi,
it's really hard to do as it doesn't happen very often and usually not for this many minutes. So for now the description will have to do.
I will send a question to garmin, it's not exceptionally important, i just want to understand how/if it can be that the unit cannot calculate the position even if it has what should be adequate number of signals locked (but only a few are GPS and more are GLONASS).
Hence, it's a question in case anyone has seen it and in case anyone knows why it is like this. Not really expecting anyone to solve anything

This peaked my curiosity.
It appears the answer is complicated:

Spoiler

https://electronics.stackexchange.com/q ... ng-modules

Thanks for article link.
Garmin replied and their answer said that it is possible to calculate the position for the unit in the scenario i described, but it could have taken more time than usual.