Update: NGS' GPS on BMs Program

All NC BMƒ??s are now Green. Glad I was able to assist with observations in access restricted locations.?ÿ

I'm not sure how to interpret the map.?ÿ Is it showing the amount of correction to the geoid model due to submissions, uncertainty in areas changed, or reduction in uncertainty in areas changed?

The two remaining in the Texas City / Galveston area are access controlled and or restricted. AW5712 would be a coup to land, great fishing opportunity. ?ÿ

AW0574 lands in the USCG facility - also a great flounder fishing spot - that requires prior authorization and clearance.

There's a Priority A mark remaining at Point Reyes National Seashore.?ÿ I'm surprised no one in the area has sat on it, it looks like a gorgeous site to spend half a day or so.?ÿ If I can find a break in my schedule...

The mark is about 400 feet ahead and to the left of this view:

The graphic above shows probable changes to the model, when the new observations are included.

I take from it that the model is still pretty loose in areas with sparse observations. You can see from the isolated dots, a single new observation can become the new "truth" for a county-sized area. Less obvious is the lack of impact in GPSBM-rich states like?ÿMinnesota and North Carolina, they didn't budge at all, and Florida only a bit, despite their adding many observations.?ÿ

I hope this evidence feeds a more realistic accuracy model. NAVD88 has some unique localized character and is truly hard to pin down. The next datum in 2022, based on GPS ellipsoid and airborne-gravity-based geoid model, will be simpler to access and understand.