Vertical Datum article - American Surveyor magazine

Very Nice! Thanks for posting.
One comment: In usgsdatumcodelist.pdf, it would be nice if the date was included just below your name. Future editions, which I believe will be necessary, could then identified by their revision dates.

The City of Pittsburgh benchmark network is based on the 1912 adjustment (Sandy Hook datum?). I doubt many people know or understand this, they just think it somehow doesn't work with NGVD29.

100 (PID KX1465):
1903: 743.941 feet
1912: 743.932 feet (used by the City)
NGVD 1929 (1943 adjustment): 744.198 feet
NAVD 1988: 743.657 feet

Thanks for the suggestion. I have put the revised date at the top of the first page. For some reason, it won't show the revision when you click on the link in my initial post, so here it is again.

http://penryfamily.com/surveying/images/usgsdatumcodelist.pdf

Looks like the mark is long gone.
http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=KX1465

So people must rely on other bench marks derived from that one, which might be of varying accuracy. Does the city provide a list of the good ones?

There's a number of historical ones still in use thanks to the Army Corps of Engineers. (Absolutely nothing to do with USGS.)

29 datum + 88 datum/2=1912 datum. full cirle in 76 years;-)

Yes, it is long gone. But, that is what the City of Pittsburgh used as its primary benchmark to start all of the leveling. The is actually a stable mark nearby (set vertical) that was directly connected to it.

The problem is that I have heard local surveyors say the city network is no good because it doesn't match NGVD29, when in fact it was done well and is simply a shift. The horizontal datum is NAD (not NAD27), so that creates confusion as well. Here is some data from a page of a powerpoint I created:

Computations performed in mid 1920’s
NAD27 was not available
Used North American Datum (NAD)
Also called US Standard Datum (USSD)
Used average of 3 old USGS stations (third order, published lat/long to 2 decimal places)
GREENTREE (PID KY3078)
CALHOUN (PID KY2064)
SHANNON (PID KY3090)
Average NAD 27 shift: -37.7 feet N; 84.6 feet E
Average NAD 83 shift: -14.4 feet N; 150.0 feet E

Excellent article, Jerry. It is obvious that you put a lot of time into researching this.

Thanks! This was actually about a 6 year project of compiling data, photos, and other information before this story finally went to print. I've literally spent tens of hours (maybe hundreds) pouring through old USGS bulletins, searching for bench marks, and putting this all together.

Excellent read, as always, Jerry!

Thank you Jerry for your hard work at putting this together.

John

Thanks for compiling the list. I don't know if I'll find much application for it, but it's good historical information. The article was very interesting.

I thought I might contribute an addendum, but now I'm not sure: B 1904 in California. See the description for JS2170. I initially thought that the date was part of the datum tag, but that might not be the case. I'll dig for a photo or rubbing.

Jim, I'm glad to see you take reporting recoveries seriously enough to have gotten your own reporting agency code. I've found too many marks with orange paint or nearby flagging that haven't had a recovery report since 1934 monumentation.

For those who don't want to bother with their own code, there is INDIV. There used to be a LOCSURV code, but I don't see it on the current form.
On the NGS site http://www.ngs.noaa.gov/
select Survey Mark Data Sheets and then Submit Recovery, which takes you to:
http://www.ngs.noaa.gov/cgi-bin/recvy_entry_www.prl

I found a 2002 rubbing, and although the cap is kind of munged, it looks like it's Datum B with a setting date of 1904:

> Jim, I'm glad to see you take reporting recoveries seriously enough to have gotten your own reporting agency code.

I got the agency code when I started doing bluebooked height modernization projects. With the help of some very able colleagues, those projects have encompassed well over 400 stations, so it made sense to use the same code for all of them. I do submit a mark recovery note or two most years, though.

I posted this link awhile back, but it shows images of other USGS bench marks with different codes. Kurt Luebke in Montana has been my biggest fan for searching for these marks. He recently found a "TF" bench mark in Minnesota which was a small isolated USGS datum originating at Taylor Falls. The American Surveyor article only has so much space, so unfortunately a lot of other cool photos of bench marks could not be shown.

http://www.penryfamily.com/surveying/usgsdatumphotos.html