Spektrum GPS sensor question
Hello all. Im a little confused here and dont want to invest the money until i have the right information. Im looking to buy a Spektrum GPS sensor. One of the main reasons is I want to see airspeed. Now, Ive read in two different posts that the GPS sensor senses speed, and will give me that information on my DX8, and another post says it doesnt, and ill need another sensor to do that. who is right? I dont want to spend the $100 on a GPS unit if im not getting all the information i want. Second, if it doesnt, what sensor to i need? hoping i dont have to get too much more, i already have the temp sensor, and tach hooked up. only got one port left on my telemetry unit! Thanks for any help you guys can give me.