Assisted GPS, using a wifi or 3G signal to assist the GPS location only allows a slightly faster location fix. After the GPS gets a location fix, it's not used at all. GPS signals from the satellites are very weak, and metal and water will block them. If you're inside, you simply can't get a good GPS signal. Moving a few feet one way or another can make a big difference, but not always. Being outside is essential for getting a good GPS signal. It's also essential that you don't put your hand over the antenna, because the water in your hand can completely block the signal. Holding the tablet in any position other than horizontal, facing straight up, can also degrade the signal, since the metal case blocks it. Putting a metal case over a GPS antenna is a bad idea, and after Asus did it, they had to decide whether to keep the metal case or make the GPS more usable. Fortunately, IMO, they decided that the metal case was more important than the GPS, so they just dropped the GPS specs from the Prime. Asus does not guarantee that the GPS in the Prime will work at all. However, the latest update, .15, seems to help the GPS reception a lot.
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