GPS Scale Factor for Total Station Traversing

Discussion of FieldGenius related issues and questions.

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GPS Scale Factor for Total Station Traversing

Post by surveyjoe » Sun May 14, 2006 11:00 pm


I have a 900 acre boundary survey to perform. I need to set about 20 RTK control points around the project to serve as a check and also the initial and backsight points to locate property corners.

I plan to set the base in the center of the project on an assumed coordinate of N 100,000 E 100,000 EL 500.00 and then set the 20 RTK control points around the project.

How do I set the GPS scale factor (and obtain the GPS scale factor) so that the EDM distances agree with the RTK GPS derived distance between points?

Is there a way to have FieldGenius 2006 (2.0.4) tell me the appropriate scale factor and store the RTK points with that scale factor applied before I traverse thru the points with my total station?



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Post by CHRIS L » Mon May 15, 2006 5:35 am

In my opion, I wouldn't worry about it unless you are dealing with a great deal of elevation difference....hundred of vertical feet between CP's

We've shot RTK points around 1000-2000 feet and less normally and never had the GPS distance vs. TS distance be off more than a couple hundeths.....the scale factor is so close to 1.00000 normally that it takes a great distance before its noticable past the average accuracy of a total station and ESPECIALLY RTK gps......but thats just my opion

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Brian Sloman
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Post by Brian Sloman » Mon May 15, 2006 9:18 am

If you localize your reference station to an existing point in your database, FG will compute the combined scale factor and set it into the transformation paramaters. You can also do this by going into Settings > GPS Local Transformation and use the "Calculate Scale (GPS)" button to compute the combined scale factor at your current position. The combined scale factor will bring grid distances to ground distances.

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