Not many, but a few:
https://geodesy.noaa.gov/CORS/SiteTable.shtml
Also this:
@norm no worries at all. My wording is not always the best. ?ÿI did remember though. The term. They use for the future is Foundation CORS that ngs will and is establishing. ?ÿThis will be for the backbone of active control not passive as i stated above. Darn little keypad on iPhone lol. ?ÿI will say the states that set up their own were very smart. That is a plus i am sure to work in a state that has many around you. Especially if they also offer rtk corrections as well.
Geoid and Terrestrial are coincident in many places in the United States. Collecting data there is not an indicator of OPUS??s accuracy where the two are not coincident. OPUS does match elliptical heights.
What is important for OPUS to match a leveled elevation is that the geoid model match the difference between ellipsoidal and the leveled value.?ÿ In the hybrid models now in use this mostly occurs on those points used to constrain the geoid model.?ÿ It doesn't matter if the geoid value is zero or something else.
?ÿ
Geoid and Terrestrial are coincident in many places in the United States. Collecting data there is not an indicator of OPUS??s accuracy where the two are not coincident. OPUS does match elliptical heights.
What is important for OPUS to match a leveled elevation is that the geoid model match the difference between ellipsoidal and the leveled value.?ÿ In the hybrid models now in use this mostly occurs on those points used to constrain the geoid model.?ÿ It doesn't matter if the geoid value is zero or something else.
?ÿ
I recently went through an RTK check on 42 control points (leveled) spread over 7 miles. Set on one then check all the others is the task. Each one was <.04' horizontally and <.06' vertically. Well within any error budget for my survey task. What struck me was how well Geoid 18 worked to the leveled data. Even 5 miles from my base I checked the north point .02' vertically. It's a big change from the old Geoid Models. We all need to thank people like Bill93 for submitting data to make that happen.?ÿ
?ÿ
In the hybrid models now in use this mostly occurs on those points used to constrain the geoid model.
?ÿ
I'm really glad we will be switching to full gravimetric rather than hybrid geoid. There are some places where the hybrid model does some really funky stuff and does not match separations observed by private-sector GNSS + levelling.
I've only seen it happen a handful of times, but each time it has been a massive headache to sort out and document for projects.
