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- Posted by: cole
the reason i localize GPS jobs is so i can also use conventional instrument on it. if i setup the job and keep it in state plane, then trying to use the total station on those points never works. im always off on my setups. maybe due to scale factor or something. im sure im doing something wrong.
Just because you are using GPS, DOES NOT mean you have to use State Plane, or any other canned projection that doesn’t “fit” what you need to do on the “ground.” GPS does NOT rely on (or use) a mapping projections (SPC, UTM, whatever) to solve positions (which by the way ARE on the ground), it’s not until you “tell” your data collector (or other software) to use a mapping projection, that you end up with trouble (except when you don’t end up with trouble).
Loyal
If you are using a projection grid like SPC or UTM it is ESSENTIAL you understand what scale factor, elevation factor, and combined scale factor are. It really isn’t hard. Grid and ground must always be carefully distinguished and properly converted one way or the other before mixing. Don’t do it until you know you are doing it correctly.
.It sounds like maybe you’re fixing the position of the RTN base station in your adjustment to values that differ from the values broadcast by the RTN.
If you setup your dc in an appropriate SP zone to collect your GPS, then set up the dc in the same appropriate SP zone to use those SP coordinates with your TS you will have no problems. The dc will do the necessary scaling. No localizations required.
If I understand your post, yes you are correct. The 6-15 feet is because the base was autonomous hence so is the rover shot. If you post process the base and rover shots they should match what you had before (how closely depends on a lot of things).
For total station measuring off the state plane points, using survce, go into equipment, localization, and check auto ground to grid. Using that option your distances will be per scale factor at each measurement location rather than a combined factor for the whole project. In Carlson survey you can set the report scale factor to either combined for the site or same as survce to report per location. So everything would be in state plane but you can label your map with ground distances. Carlson survey north arrow will show north at central meridian of projection, convergence (north at your location), and magnetic (difference from north at your location) if you check those options.
Working with deeds, plot them in carlson survey, make a block, scale by combined factor ground to grid.
Working construction it gets a bit too complicated for a quick post.
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