Quote:
Originally Posted by Geronimo '74
Is that with or without the use of a ref station Glen??
Or does it have a file with corrections already preloaded or sent to it via radio??
Or has stuff evolved so much since my hydro survey days that ordinary GPS is almost milimeter accurate?
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Ordinary GPS is not that accurate. You need to buy the survey grade stuff to get professional results.
There are ground transmitters and a entire network of signals to use as reference. The surveyor friend said that you can detect the growth of the tripod with the GPS from heat if you start it in the shade and leave it there for several hours as the sun moves and heats it up. I don't know if that is true or he was just pulling my leg.
With the math that the computer does with the airborne signal and all the triangulation while flying along at 110 knots ground speed the program knows within a couple of feet just where the airplane is in X Y & Z axis. The GPS records it's position every 1/2 second and records that to the data card, it also records when the camera fires. We shoot in stereo usually 60% forward overlap and 40% side-lap & if we have good ground control targets at the corners of the project we can build a 3D model of the ground with one foot accuracy over a large swath of land. If it is rugged terrain with large amounts of ground elevation changes we can map an area a ton cheaper than a ground grew.
We would love to play with the new LIDAR systems but they are over a million bucks. We can burn a lot of film for that.