>local Geoid data set loaded Is this something most GPS radios would have? Or just higher end ones?
Josh Luthman Office: 937-552-2340 Direct: 937-552-2343 1100 Wayne St Suite 1337 Troy, OH 45373 On Wed, May 6, 2020 at 10:36 AM Brian Webster <i...@wirelessmapping.com> wrote: > OK here is what I learned from my brother. > > > > You want to use the Geoid values, however you also want to make sure you > have the Geoid model loaded in to your Trimble R8 GPS. (for those not > paying attention that is a survey grade instrument with cm accuracy). > > The geoid numbers are tied to the map projection you are using and they > are also tied to the GPS ground stations you are connected to 9necessary > for the cm grade accuracy). The Ellipsoid values assume that the earth is > perfectly/mathematically round. Geoid values correct for the fact that it > is not perfectly round and the reason why your GPS needs the local Geoid > data set loaded before you take readings. You do have the Geoid data for > your area loaded don’t you? > > > > For radio mobile you will want to use the Geoid height converted to meters. > > > > Is there LIDAR data for the area in question? It might be easier just to > use a value from that. Might also be nice to convert the LIDAR to a file > format for Radio Mobile and use all that data (going to need a lot of disk > space though). > > > > Thank you, > > Brian Webster > > www.wirelessmapping.com > > > > *From:* AF [mailto:af-boun...@af.afmug.com] *On Behalf Of *ch...@wbmfg.com > *Sent:* Tuesday, May 5, 2020 2:12 PM > *To:* af@af.afmug.com > *Subject:* [AFMUG] Elevation question > > > > I have a pretty good GPS receiver. Trimble R8 with a Yuma data > collector. Normally we use it only for lats and longs. > > It is corrected in real time with a cellular data modem and a RTK/VRS > ground station network. > > > > Yesterday we did a shot from a hill that did not exist when shuttle radar > data was taken. It was way off in elevation. > > So we took a shot from our parking lot and compared it with what we think > we know to be the altitude as well as our cell phones and google earth. > > > > Turns out the R8 has an ellipsoid height as well as another height > associated with the northing and easting values. > > The second one seems to be more in line with what I was expecting. > > The local dealer sent me a drawing showing this. (attached) > > > > So now I am super confused. Not sure what number to use when working with > Radio Mobile. Do I add the geoid height to the ellipsoid height? > > > > Was hoping Brian Webster may know or others may know. Googling google > earth elevation talks about different versions of geoid. Not sure if their > elevations are geoid elevations or not. > > > > So, rather than dig into it any more I am taking the lazy approach and > posting the question here. > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com >
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