Do you have to buy an aviation GPS?
I use a Garmin 182c in our JetRanger installed as loose equipment.
Itīs really excellent with a very detailed map and very good to use for seismic work, which we use it a lot for.
It has the "Road in the sky" feature which is excellent when you have to fly search patterns for measurement work and also good to get between A to B.
We hook it up to our Laptop to download & upload tracks and waypoints or to use while flying with a laptop PC.
I absolutely love it and it only costs about $1000.-