Ralph, thanks for the good link. I was thinking gravity measurements were taken on the ground. In an airplane you could sure cover a lot more earth.Da...

Melita,That exactly answers one of my questions. Thanks for the link.Dave

Thanks All!I greatly appreciate all your replies. It's helped me to better understand this formerly impenetrable subject.I love this forum!Dave

Thanks, Loyal."Two “points” with the same geopotential number, will NOT (necessarily) have the same Gravity Value."Interesting. Can you elaborate on t...

Thanks, Colin."The 2 together - datum and ellipsoid creates the 2D reference frame. Add a geoid and you get a 3D reference frame."I like that descript...

Thanks, Shawn,"$#!t still runs downhill and payday is still Friday."I guess geodesists need a paycheck too. 😀 Dave

Thanks, Melita!Good links. Just the sort of thing I've been looking for.Dave

Thanks, Ralph."In order to get into this stuff in depth, you're going to have to study things like orthometric height, ellipsoid heights, deflection o...

Thanks, Moe.On whether a Geoid can influence horizontal position, certainly leveling a total station or plumbing a GPS rod will affect measurement nex...

Thanks Tom. That helps.What you said got me to thinking that two points at exactly the same height above an ellipsoid might have different gravitation...

My bad, Shawn! OK, limited checking, no OPUS, no boat-rocking, and don't offend any of the keyboard surveyors!How's that?Dave

Dammit, Kent! MM has told you again and again that the control is perfect and doesn't need to be checked. That surveyor should just STFU and stake the...

MM,What am I missing? Help me to understand."This guy went out and declared all the control unusable, the control we just got done checking which was ...

MM,I'm not the least bit "confused," but I'd honestly like to know what you have against OPUS. OPUS solutions are longer-duration observations than fa...