测量基本原理.ppt

全站仪和GPS测量原理简介 2011年4月—南京 One way of positioning 2 Known Points, 2 Known distances FIND WHERE YOU ARE! Another way of positioning 2Known Points, One distance to the unknown point One angle Another way of positioning 2 Known Points, 2 Known distances from unknown point FIND WHERE YOU ARE! Positioning-Opticals BUT… Problem occurs! Positioning-Opticals Because, forPositioning-Opticals The target must be seen! GPS then… 2 Known Points— Satellites 2 Known distances from unknown point (computed) What is GPS? BUT again… GPS can’t do everything In the forests In the tunnel under the buildings Any place that you can’t SEE enough satellites or PDOP is poor! Rover So people must use opticalsGPS and Opticals are complementary * What does GPS do for us here on earth? c GPS was originally designed as a global navigation system to provide accurate navigation for the United States military. c To serve this basic function, the GPS satellites act as reference points, in space, for computing positions on the surface of the earth, accurate to a few meters. c In reality, using advanced differential GPS methods – it is possible to compute positions to better than a centimeter accuracy. These advanced applications will be discussed in more detail later. * I’d like to point out the previous statements with another slide. This is a simplified drawing of a survey site. An optimal point for GPS observation is not inevitably an ideal point for TS observations.We will set up the TS where the best terrestrial sights are available. This could be under bridges, close to building or – as shown here – beneath the trees. Mouse click Use of GPS In case there no terrestrial control points available, we can quickly create some with our VRS Rover, temporary or permanent points. These new points can be used for TS resections. The TS is ready for stake-out, etc. immediately. We can carry out GPS observations in all areas which are not affected by obstructions. We also use GPS wheneve