The reason for inreach mini poor gps performance compared to other units/phones

Why do you assume the mini uses GPS satellites? It has IRIDIUM embossed right on the antenna, thus I assumed it only uses the 66 IRIDIUM satellites in LEO for location calculation as it already uses those satellites for communication services.

I suspect the lack of GLONASS in the GPSMAP 66i is due to the addition of IRIDIUM satellite system antenna and receiver. GALILEO is superior to GLONASS, thus GALILEO was kept and GLONASS dropped to make room for IRIDIUM.

Iridium satellites do not provide a basis for position calculation. They are strictly for communication. In fact, the number of satellites overhead at any given time is insufficient for trilateration even if the system was otherwise capable of it (which it is not).

I wondered about that....

I can't actually say for sure just which GPS systems the Mini uses. The OP does not cite his source for GPS only. I suspect it's correct, if only because (AFAIK) the unit does not provide settings to control the system(s) in use. But that's an assumption.

twolpert said:

Yes, it would help. However, 20% of a few minutes is not a huge amount of time.

Its more than 20% faster.  That’s just if you add Glonass and GPS together. = 65 satellites.  Modern mobile phones use (GPS, Galileo, BDS and GLONASS and more). Over 128 satellites.

I’ve had situations where my phone (in flight mode) obtains a location lock within 30 secs and I’ve been standing around for 20 mins waiting for the inreach to get a lock.   This usually occurs in mountainous terrain/canyons which inhibits line of sight to satellites. 

Even if Garmin cant upgrade the mini due to hardware limitations, there is no reason why they cant code the earthmate app to allow use of the phones location for a minis location fix when they are paired together via Bluetooth..

twolpert said:

. Even when you can get a fix, you may not be able to communicate with the Iridium satellites.

Agree however ive had situations (probably 1 out of every 5-8 msgs) where I have a iridium lock but the mini ask me if i still want to send the message because it does not yet have a location lock.

Hi. I recently bought a Mini to use as an alternative option to my SE+. I noticed that the Mini seems to struggle for very long periods sending preset messages, especially when I am moving fast (flying in a sailplane) - it keeps on saying GPS reception is poor. The SE+ has no such issue. The locations, weather conditions and mounting options were much the same. Do they use a different satellite system, or is the radio/antenna in the Mini not as powerful as in the larger models (SE+ and Explorer)?

As noted above, there are a variety of possible reasons for the Mini's acquisition behavior. I am sure that antenna design and GPS chip set play a role.

I don't have any experience with high-speed travel (anything more than 40 or 50 mph). I suspect that the Mini's attempts to conserve battery power may also play a role. The mini attempts to acquire a fix only when it needs to (for example, to send a track point or to update the navigation screen if displayed). Refining the fix (reducing estimated positional error) is an iterative process which the Mini probably tries to minimize. When you're moving quickly and acquiring a fix infrequently, I would guess that it's possible that the unit rarely converges to a decent quality fix - perhaps because you've moved too far in the time it takes the device to iterate toward a decent fix.

I have no actual facts to back this up. I have not seen any other reports of this behavior. It might be worth a call to tech support to see if there is a design limitation here, or if there might be a problem with your particular device.

Thanks. Speeds are around 75 mph. My tracking log interval was set to 1 minute. I will change it to 1 second and see if there is an improvement.