GPS Help

Joe · Dec 8, 2016

Let me start off by saying this. I have had the Mavic for about two weeks now and I love it. Yesterday while it was doing its initial start up, it was not getting any GPS signal. I take off from the same spot every time I have taken off so far and have never had this issue. I will say this, this is the first time it initiated an IMU calibration during start up. It eventually grabbed 9 signals and let me fly in GPS mode. Also...FYI Active-track does not work with a low GPS signal. Has anyone else had this issue? if so please help.
Thanks
Joe

halley · Dec 8, 2016

Is your usual take-off area wide open to the sky, or is it surrounded by buildings? GPS satellites are constantly moving across the sky and you need to see 4, 5, 6 or more to get a great GPS position for ideal IMU performance. If you're packed between two houses or surrounded by the hills, you're reducing the amount of sky and therefore the time each GPS satellite is in view.

F6Rider · Dec 8, 2016

halley said:
Is your usual take-off area wide open to the sky, or is it surrounded by buildings? GPS satellites are constantly moving across the sky and you need to see 4, 5, 6 or more to get a great GPS position for ideal IMU performance. If you're packed between two houses or surrounded by the hills, you're reducing the amount of sky and therefore the time each GPS satellite is in view.

This should not be a factor unless you are at the North or South poles or have restricted access to the sky as you mentioned. The GPS satellites are at roughly 20,000 miles altitude with a 14,000 mph speed so an orbital time of about 12 hours, with the number of satellites in the constellation you should be in line of sight of at least 10 satellites at any given time. This can drop to 8 given variances in weather or if any sat's are in maintenance mode, and is normally 16-18 and can be as high as 22.