# How GPS coordinates grows?

I'm working on a project which uses GPS coordinates. I have a UAV that flies, for example, over a meridian or a parallel. I suppose that the coordinates I'm reading from UAV are always increasing or always decreasing, but it isn't like that. In details, I can have for example 3 decreasing coordinates and 1 increasing coordinate, then (always for example) 10 decreasing coordinate and 1 or 2 increasing coordinates. Is that normal? It could be the precision of the sensor?

• That will depend on the direction your UAV is flying, if it is going Straight North, no deviation from the North (0 Azimuth), then your longitude will remain constant only your latitude will change. I assume by GPS coordinates you mean latitude and longitude here, or are you working with northing and easting? Commented Feb 28, 2016 at 11:40
• Yes I thought that one remains constant and the other increase or decrease, but sometimes the value that changes (lat or long) is like its "jump" back or forward. For example, suppose I have increasing coordinates like (10,15) (15,15) (20,15) (25,15) (of course these are fake coordinates for simplifying the example) and sometime I get (10,15) (15,15) (20,15) (15,15) (25,15). Is this normal? Commented Feb 28, 2016 at 12:17
• I would also say it depends on what is the projection you are using and what kind of increase you have ! can you give us those details ? Also have you tried to map them ? It would be interresting to see if it follows and general pattern or if it's definitly not realistic. Commented Feb 28, 2016 at 15:57
• Your assumption is correct. You must have some noise in GPS measurement data which is normal especially if you have fix to only few satellites. Commented Feb 28, 2016 at 16:45
• @user30184 since my sensor take 10 to 100 coordinates at second, could be the average of these coordinates a good approximation in order to avoid the wrong value taken? Commented Feb 28, 2016 at 17:20