The app reports what the GPS resolves as latitude and longitude and demonstrates how the device accuracy might vary as the GPS updates its satellite fixes, or as the device is moved from outside to inside a building or loses a fix on the satellites it uses to determine location. Small accuracy values indicate better accuracy. The logger app captures latitude/longitude positional data and provides a numerical estimate of the reliability of the GPS' satellite fix ( Accuracy). Many simple devices will only use a few satellites. Some GPSes can use from between 12 and 20 satellites to get a very accurate fix, providing the GPS receiver is capable of receiving 12 or 20 channels of data. The LocationSensor component instructs the GPS receiver in the mobile device to get a satellite fix (find a satellite, determine that the information from the satellite is valid, find at least two more satellites to confirm the information, and only then report the information back to your device). The app also demonstrates how the accuracy of a device's GPS varies depending on where the device is located. GPS Accuracy Logger is an app that demonstrates the use of a device's Global Positioning Satellite (GPS) receiver. Geo-location principals are described near the end of the tutorial. You will do your best job of developing apps using the LocationSensor if you understand how a GPS system works. As you develop apps with this tool, be aware the GPS in your device can do a lot, but its accuracy is limited in many situations. There are techniques to make the resolution better. The best accuracy possible with specialized GPS receivers is approximately three meters. Therefore, satellite positional information is precise to 0.9 meters. Looking at 0.00001 of a degree of latitude, it converts to 0.9144 meters. These are awkward units for use on a computer, so developers and others commonly use decimal latitude and longitude descriptions, to make the math calculations easier. Latitude and longitude are still described in terms of degrees, minutes and seconds. The spacings between degrees of latitude are constant the spacing between degrees of longitude are variable.Ĭurrent app developers think in terms of meters, but a long time ago, navigators described their ship's position with respect to the English units of degrees, minutes and seconds.
A degree of longitude is sixty nautical miles at the equator, but the separation between adjacent whole degrees of longitude diminishes as you change latitude toward the poles. This means that the distance between a degree of latitude and the next whole degree is sixty nautical miles. Think meters!Ī nautical mile is the distance subtended by a minute of angle (1/60 of a degree) across the earth's radius. Calculate everything in meters, then convert to report the result in feet or miles on your display. If your app must deal in English units, use the Math blocks to convert units at the time you display them. When the sensor reports distance information or you set a distance into the component, the units are in meters. The measuring units employed in the LocationSensor for distance are meters. Location means the device's present latitude and longitude, or it can mean your street address. Finding a location through the network uses very different techniques than with a GPS. The sensor can also work with network/wifi location services. When the LocationSensor communicates with the built-in GPS receiver, the GPS determines the location of your device. The LocationSensor is used to communicate with the global positioning satellite receiver (GPS) in your phone/tablet. The LocationSensor component is a simple control that is difficult to use without knowledge of some basic concepts of geo-location.
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