Uncovering history through National Coast and Geodetic Survey benchmarks

Gads it has been a while. Between conferences, work and play, I let this site languish a bit. Well, here is a cool thing to do and not a rant.

In walking around, do you ever look down and see a small circular brass marker that are embedded into rock, concrete or even buildings. They were placed by the National Coast and Geodetic Survey and are survey benchmarks.

A good description of these benchmarks can be found at:

Many of these were surveyed and planted there at the turn of the last century. As there has been some time elapse since most of these were established, there is some interesting history that can be gotten by looking up these sites and reviewing the data sheets for each marker. Fortunately, the National Geodetic Survey (NGS) has this data on line. By going to:

and entering your longitude and latitude and a radius of the area you want, you can get nearly all of the markers. I say “nearly” as I have found markers that are not in the database. Once you get the listing of markers in your area, tell the page to get the data sheets for the markers. Each data sheet is a bit messy to ready and you can get some guidance on how to go through them from the “peakbagging.com” URL above.

Once you have the data sheets, try to find the markers. It is much like geocaching in tracking it down, ‘cept you don’t leave or take anything once you find the spot.

What has been interesting to me when I have gone looking for the markers, is the history of the site during the time the markers have been established. Looking at the data sheets you can see the descriptions of the site at the time it was established and when they revisited the site every 30 years or so. You will find the changes in the area documented in these sheets. For instance, living in San Francisco, I was interested in seeing markers in my area. What I found was a establishment of a long forgotten overseas radio station near my house on Ocean Beach or be able to review how South of Market had changed from a massive Southern Pacific rail yard to a trendy geek enclave.