Dpos and Giodis

Duane Frymire

Active Member
sort of related. My LS page is set to Geoid 12B, but DPOS from the LS returns saying Geoid 18 used.

I put in wrong antenna height when starting the Base of 6.91' vertical, when should have been 4.51' slant. Didn't matter in the field because I did a shift on known location previously surveyed by me and then checked into a USGS benchmark and agreed within 0.08' of published value.

So downloaded the jps file and processed through the web service DPOS entering correct antenna height. But that doesn't agree with the shifted in height or the BM height by the antenna height difference.

So DPOS from the LS and it does return correct height that agrees with shifted in height and BM height. In spite of the fact the antenna height is incorrect.

DPOS in either case seems to know the correct antenna height in spite of my mistaken entry? My attempt to fix it on the web service instead turns it into a mistake.

Or could there be 2'+- difference GEOID12B to Geoid18? If I recall the maps it should be around 0.25' in this area.

I'm comfortable with grades I set because of agreement with BM and DOT agreement on BM, but confused what's going on. I can't load both a profile for 12B and one for 18 on the LS (one just overwrites the other because other parts of coordinate system are the same). Also can't see a way to process 12B instead of 18. BM, DOT, and FEMA stuff is 12B, so need to know what it is I'm getting and a way to compare.
 
Top