Κάπου είχε πάρει το μάτι μου οτι για να δουλέψει το GPS έξω πρέπει να κλειδώσεις με DATA! Είχες πρόσβαση σε internet (wifi ή GPRS?).
Δεν νομίζω οτι έχει σχέση αυτό. Κανονικά θα έπρεπε να κλειδώσει μόνο από τους δορυφόρους.
"
Satellite GPSIn regular GPS (unencrypted civilian L1 1.57542 GHz signal), reading and calculating your location takes time (getting good data lock on a minimum of 3 satellites and calculating your position takes about two minutes and can last up to five minutes for all satellites). The iPhone reads the C/A-code (Coarse Acquisition) GPS data from the satellites to get your position. Note that the iPhone can not read nor use the more accurate encrypted P-code (Precise) GPS data broadcasted on L1 (1.57542 GHz) and L2 (1.22760 GHz). You normally must have a clear view of the sky to get the satellite signal (sometimes the satellites are in the sky on the horizon, sometimes above you).
GPS in Google MapsWhenever you are using satellite GPS, there is an animated blue outline of a circle that grows bigger and bigger until it disappears and starts small again from the blue dot.
To ensure you are using satellite GPS, you can take out your SIM card (turn off 3G as well), turn off Wi-Fi, and turn on Location Services. Then turn off and on your iPhone, and go into Google Maps app. It should complain with a popup after a while. Close the popup and hit the bottom left location button, and it should start spinning. After about two minutes you should get your first satellite signal, and you should see a blue dot, a transparent greyish circle covering the map, and an animated blue circle outline. About every 100 seconds after, you should pickup more satellite data, which will make the transparent circle smaller. If you lose a satellite, it should make the circle bigger. The smallest can probably circle a tiny house. On average, it can circle an apartment complex.
Note that for this example, since you don't have any cell signals or Wi-Fi at this point, you can't download map data. So to test satellite GPS, you should use a cache of the map data already downloaded for the area you are trying out, which requires that you pan around many city blocks on all the different zoom levels before turning off Wi-Fi (and/or removing your SIM card).
Cell Tower TriangulationThe iPhone also supports Cell tower triangulation assisted positioning. All cell tower locations are known precisely, so if your iPhone is communicating with one (in either GSM or 3G), you can pinpoint your location to roughly 1500 meters. Normally, you can detect 2, 3, or more towers, which you can use triangulation to pinpoint your position fairly quickly (fixed towers don't move around, so first rough location can be gotten and calculated in 10 seconds or less). Most assisted GPS use data from cell tower locations. This calculated data is most times less precise than waiting for satellite data.
Cell Triangulation in Google MapsTo test out cell tower triangulation in Google Maps app, simply turn off Wi-Fi (and 3G, as GSM works fine) and stay indoors (roof over your head) away from all windows. Make sure Location Services is ON. Turn off and on your iPhone and go into Google Map apps. You should get a blue dot in less than 20 seconds with a transparent grey circle covering about a city block (can fit about 30 apartment complexes inside the circle). It is usually not very accurate with your location. The circle can move around (sometimes long distances two miles away, so zoom out) and grow bigger or smaller depending on which cell towers are picked up by your iPhone. On worse cases, with only one cell tower, you may end up with a huge circle covering a whole town (especially deep inside thick walls). Once you move outside with a clear view of the sky, the animated blue circle outline should show up about two minutes later when satellite GPS is picked up (making your transparent circle small again). Note that the positioning of the GPS alone is different from GPS + GSM tower triangulation (but not by much).
WPSIf you are using a Wi-Fi access point, the iPhone can get your general position by getting the location of the actual Wi-Fi hotspot. The technology used here is called Wi-Fi Positioning System. It is basically a database (owned by Skyhooks company) that stores the MAC of the Wi-Fi access point you are connected to and links this MAC to a location. The location is actually entered by Skyhook company's cars going around all the roads searching for Wi-Fi signals. People can also input their Wi-Fi access point's location using the company website. Most Wi-Fi signals only work within 20 meters (with walls) to 200 meters (no obstacles), so your positioning is not too bad (but also dependent on whether the location was entered into the database correctly). The location can be wrong if the Wi-Fi equipment was moved from one area to another without updating the Skyhook database.
WPS in Google MapsTo test out WPS, simply remove your SIM card (and turn off 3G), turn on Wi-Fi and Location Services. Find an access point, and connect to it. Go into Google Maps app. Note that because the database is not updated frequently, and sometimes errors on wrong user input, wrongful results often (especially if the access point was recently moved from another location)."