Gps on BM

https://content.govdelivery.com/accounts/USNOAANOS/bulletins/2fce65b

GPS on BM observation instructions

4+ hours is still required.

I am glad to see this is getting extended.?ÿ I have 2 BMs near here that I have been trying to work into the workflow, but just haven't had the time.

Quick question, I set up on a bench mark that doesn't show up in the NGS file. Is there any reason to submit that? I've only done ones I feel are uncompromised and are in the data base.

@mightymoe?ÿ

I believe itƒ??ll be incorporated regardless of the wish list.?ÿ

I pinged NGS specifically asking if 2 hrs Z-XII is acceptable?ÿ

In my experience, NGS will try to use data on any mark they have a good classically measured orthometric height for, even if it isn't on the wish list.

There are marks in their data base with less reliable categories of vertical data, and marks that only have GPS-derived heights, that won't be used.

Of course, they can't use data on marks not already in their data base (lots of the USGS marks, etc.) unless you go through the Bluebook process and give them both leveling and GPS data.

@bill93?ÿ
so, choose wisely. Old BM leveling lines. What needs to accompany the observation is reliable description of the HI, and condition of the mark ?ÿ

Even 2nd order??ÿ

Even 3rd order, if they are believed to be stable and don't look like outliers.

@bill93?ÿ

I don't know what class this mark is, for some reason it's not in the NGS data-base. I have a book of level runs that cover a large area and many marks not in the data-base are in my book, but this area is outside my list. I used to track down level-runs through the USGS office in Denver but haven't in a long time. I don't like sending in data if the bench mark is questionable.?ÿ

Only a small fraction of the US Geological Survey marks were included in the National Spatial Reference System as defined by the US Coast & Geodetic Survey, now National Geodetic Survey.?ÿ This is true over most of the country, and typically this was because looser procedures were used to densify the network for USGS mapping.

@bill93?ÿ

Yeah, USGS leveling isnƒ??t primary control.?ÿ

I don't see GPS on BM going away given what it's being used for. Don't tell anyone I said that.?ÿ

I see why 4 hours is required with 10 GPS tracked. But with 45 on a full constellation, 2 hours should be fine.?ÿ

@oldpacer?ÿ

NGS is still working on adding constellations other than GPS to OPUS so you will not have more than about 10 sats.

If you get 2 hour occupations on marks, NGS will use it, just not the same way as 4+ hour occupations.?ÿ See page at web address below.

https://www.ngs.noaa.gov/OPUS/about.jsp#sharing

?ÿ

Edit: the website does say 4 hour minimum.?ÿ I was convinced that I heard a presenter at the PLSO conference say that 2 hour sessions would be used, but not with the same weight as 4 hour.?ÿ Maybe I heard wrong.?ÿ It seems like 2 hours of good data would be better than no data....

NGS OPUS-S will process sessions of 2 hours or more and give you the results, but I don't see anything that says NGS will use your results for?ÿ their purposes if it is less than 4 hours.

The doc says for GPS on BM: must be 4 hrs.

I wouldƒ??ve thought that in areas with many CORS sites, 2+ hrs be useful. Particularly with precise ephemerides. And the solutions weighted by the residuals, data quality, etc. I have geodetic antennae and the venerable Z12s. I donƒ??t believe a newer receiver has much better phase resolution, which is the critical part.?ÿ

So if I post the data, next day, and get an opus shared solution, with 4 hr, will NGS reprocess with precise ephemeris, or should I upload AFTER the precise eph is available??ÿ

I wish they would issue some sort of warm fuzzy that the 4-hour session I did in April, 2021 and reprocessed in early January, 2022 is actually being used. ?ÿI log onto the nifty GIS application and still see the same blue 10km hexagon. ?ÿNo indication that my data has been used, beyond the OPUS results email and the successful receipt of the data sheet update email with one question about a photo but no follow up to my response, and no official update of the hexagon or the data sheet. ?ÿI guess they are just as overwhelmed as the rest of us.

Posted by: @larry-scott

should I upload AFTER the precise eph is available??ÿ

In one of their webinars I heard that they don't recommend submitting when only "Ultra rapid" results are available, but "Rapid" is sufficient and you don't need to wait for "Precise", which can take up to 2 weeks.?ÿ They may or may not reprocess before the final conversion tool is finished.

Next day may not be good enough - Rapid is usually available in the USA afternoon on the day after your session, unless your session went past UTC midnight.