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

So like many people on this forum Ive found the time the Inreach mini takes to aquire a location fix to be ok but not great.  My mobile phone gets a location fix much faster than the mini.  (phone has all location assist services turned off and is in flight mode)

I think i found the reason.

The inreach has access to 34 orbiting satellites (GPS only)

My phone can communicate with 123 orbiting satellites to triangulate a signal (GPS, Galileo, BDS and GLONASS satellite constellations)

Thats a huge difference.

So can the mini be upgraded via software patch?  or can the garmin earthmate app be improved allow the mini to use the phones location for a fix when connected via bluetooth? 

This would speed up location acquistion time in an emergency and in general navigation and messaging.

It could make the difference between life and death in a scenaro where a person is located in a canyon and out of the line of site of the closest gps satelite orbit.  Then mini  would need to wait minutes or in a worst case scenario hours for another GPS satelites to pass directly overhead. 

In that time several of the satelites of the  other location service constelations like Galileo, BDS and GLONASS could have passed overhead but the mini currently cant talk to them.

Garmin says that adding just GLONASS 31 sats to the GPS's 34 sats decreases location acquisition time by up to 20%
https://support.garmin.com/en-AU/?faq=G ... ErPJevmbJ7

Imagine how much faster it would be if the inreach could talk to GPS, Galileo, BDS and GLONASS satelites either via a software patch or via the earthmate app using a phones location fix.

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

    Poor sky view is a problem no matter what. More satellites in play improves your chances - but you can't get around the minimum requirement for 4 satellites in view, for a sufficient amount of time, in a suitable geometry. If you're hiking in challenging situations like this, your best defense is going to be sending track points frequently. That way, SAR has a starting point even if you cannot acquire and transmit a current fix.

    Finally, note that the Iridium network used for messages, tracking, etc. is a completely different set of satellites. Iridium is much touchier in difficult conditions (such as the slot canyon you mention). Even when you can get a fix, you may not be able to communicate with the Iridium satellites.

    Never say never. But even the most recent iR handheld device (the GPSMAP 66i) supported only GPS and GALILEO at initial release. I don't think the chances of an enhancement like this for the Mini are very good.

  • 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 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.

  • 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..

    . 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.