So I discovered our new data collector has built in GPS that you can actually collect data in.?ÿ?ÿ Our new data collector is a Ranger 7.?ÿ So if I have a job set up for state plane coordinates zone Illinois West, the horizontal coordinates are within a few feet of being correct but all the vertical data is about 100 feet to high.?ÿ I'm also using a geoid model, and the geoid separation in my area is around a 100 feet.?ÿ Its almost like the geoid model is being applied incorrectly with the built in gps in autonomous mode.?ÿ Not a big deal since I don't actually use the built in GPS for anything except NGS monument search.?ÿ?ÿ Any ideas on why the 100 foot vertical error?
You say there is a 100-foot difference??ÿ I would say you're on the right track thinking it has to do with the geoid model incorrectly applied.?ÿ Try disabling/deleting the geoid model and see if you get different results.
Yeah, I thought of that.?ÿ I just need to try a couple of different things.?ÿ When its using the built in GPS, I'm not sure exactly how that works compared to or RTK base rover setup.
My Garmin gets the ball park elev. without a geoid setting.?ÿ Perhaps it's doing a built in elev. calc.?ÿ with the built in GPS.?ÿ
Garmin have a geoid model. Mine are old, so they have EGM 96. I assume the new ones have EGM 2008.
Just guessing, but I would say that the DC applies geoid separation to RTK measurements but not to readings from the built in GPS. The reason being that the on board autonomous GPS receiver is ITRF (hence the need for EGM) while RTK is NAD83, which your geoid model (GEID12B) is designed for. So unless it has the EGM96 model, it would not be able to correctly obtain ortho heights from ITRF autonomous positions.?ÿ
As for Garmin using EGM08 now, I doubt it. The EGM08 model is too large, and the improvement over EGM96 is probably well under the accuracy of an autonomous position. My R10 which has RTX (cm accuracy) still uses EGM96 on board, I believe that is due to the model size. But I am not 100%sure that is the reason.?ÿ
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