Do civilian GPS units give accurate altitude readings? A friend of mine said that the government does not allow civilian GPS units to receive accurate altitude data. Supposedly the feds don't want GPS used for missile guidance.
I was trying to use my GPS to take altitude readings in my yard and the altitude was varying all over by up to 100 feet when the GPS was sitting on the ground. It would settle on a number for maybe 15 seconds and then it would be all over the place again and finally settle on a totally different number.