What the heck is an azimuth?

I generally like my job on most days but every once in a while it positively fills me with glee. This usually involves something either deeply strange or so tiny as to be nearly trivial (or both). This time, though, the occasion of my mirth turned out to be something hiding in plain sight.

I had a very nice visit a while back from Philip Walters, ’76. While he was here we went for a walk around campus and I listened to him tell me things I didn’t know. As we walked he pointed this out to me:

Geodesic survey marker

That’s Philip’s shadow.

It’s in the sidewalk between Lovett Hall and the statue of William Marsh Rice, which is, I believe, considered by most to be the exact center of the universe. I’d walked past and over it thousands of times and never given it a thought.

It turns out that the metal plate hides a station placed there by the National Geodetic Survey in 1942. A link to their website is here but for those who don’t want to go digging, here’s a screenshot of the page that shows its exact location:

Screenshot 2015-11-27 15.51.42

I don’t really know anything about this stuff but I kept poking around and found the data sheets for this marker, which proved more interesting yet. They provide a sort of short history of the station and also pointed me to other markers on campus: two reference markers in the quad and an azimuth marker. Here are the sheets as a pdf:

DATASHEETS

I easily found the azimuth marker embedded in the granite at the base of the main gate at entrance 1:

IMG_1192

It was a bit of a struggle to locate the two reference markers in the quad but I finally found them several inches down with the help of my metal detector. (I just knew that thing was going to come in handy some day!) In the meantime, Philip made an inspired guess, blew up one of the aerial shots I’d posted of campus construction in 1948, and discovered that you can actually see the markers as three fuzzy white dots:

Three Marks in 1948 air photo

I’m incredibly grateful to Philip for making this delightful adventure possible.

Note: I actually do know what an azimuth is.

Bonus:

IMG_1270

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14 Responses to What the heck is an azimuth?

  1. I am glad you enjoyed the hunt! They chose a good spot for that triangulation point back in 1942, where the sight line from the Station to the Azimuth mark was unlikely to get blocked over the years, although it went from being surrounded by a grass court protected by hedge to being right in the middle of a sidewalk.

    • Important survey stations such as triangulation points usually have a couple of reference marks set nearby, so that the three marks form a triangle. The distances between the marks are recorded. This allows a mark to be replaced quickly if one is disturbed or destroyed, by simply laying out the triangle from the two remaining marks.

      Replacing the Azimuth mark, which was done in 1963, would be a more involved process. A sight line would have been established to another mark at a known accurate geodetic azimuth, or a corrected celestial azimuth could be used, but normally a terrestrial geodetic reference would still be checked, comparing the reference to the azimuth from the Station to the Az mark.

      This may have required a survey tower to be erected over the Station mark in the Quad in order to get a sighline to one or two other triangulation stations. I had mentioned to Melissa that I remembered seeing a survey tower in the Quad when I was a kid, but I’ve not been able to find a photo or reference anywhere online. From the history on the Datasheet, it would seem that 1963 would have been the event that might have required a tower to be set up. They could be set up in a day, and torn down in a day, so it would not have been there any longer than the time it would take to place a new Az mark. Does anyone else remember seeing a tower set up in the quad in the 1960s?

      • I just found out what the “HEIGHT OF LIGHT” phrase means in the Datasheet notes. I found it in a geocaching discussion board http://forums.groundspeak.com/GC/index.php?showtopic=96421

        It is a record of how high an electric lamp was installed on the survey tower, to be observed from other points at night. So, if there is a “HEIGHT OF LIGHT” noted, there was a survey tower erected over the Station. There is such an entry noted for both 1963 and 1968. So, I could have seen a tower in 1963, OR 1968. 1968 matches my recollection better.

  2. Dagobert L. Brito says:

    You had me worried about STEM education.

  3. Interesting that the US Power Squadron is checking on the markers. They are a boating organization. Maybe they are preparing for the next flood.

    http://www.usps.org/

    • US Power Squadron used to have a volunteer program to “recover” (Inspect) various survey marks, but the program faded out in the first decade of this century. The Geocache hobby now takes up that role, and submits recovery reports. Anyone can submit a recovery report to NGS, and I sent Melissa the link so she can too.

  4. baileynhtx@cs.com says:

    “A link to their website is here but for those who don’t want to go digging, here’s a screenshot of the page that shows it’s exact location:” Melissa, Melissa, Melissa, the possessive of “it” is “its.” Sorry to be so picky, but it’s one of my pet peeves.

    • Melissa Kean says:

      Picky is ok around here. I’ll fix it for you!

    • francis eugene 'gene' pratt says:

      In my early days of grammar (Memphis, Tenn.), I learned at the nuns’ knees that only humans could have a possessive form.
      My sweetie pie remembers being taught (Orange, TX) that animals could also have a possessive form.
      We were both taught that inanimate objects did NOT have a possessive form.
      I wonder how Willy Snakespear wrote it.

  5. A fun poem about Coast and Geodetic Survey, NGS’ predecessor who set the mark.

    http://www.history.noaa.gov/art/cgs.html

  6. Bill Johnson '57, '58 says:

    When I took an advanced surveying course from Dr James Sims in probably the fall of 1956, he had us looking for a marker in this area. As I recall we did not find it and were looking closer to Fondren in the gravel walk. He had some notes that we were following that had been made when he was a student I believe. I think he concluded that the marker must have been destroyed…

  7. loki_the_bubba says:

    Why did you not remove the metal plate and show us the marker?

  8. almadenmike says:

    When I was in high school in suburban Washington, D.C., I’d get description lists from the Coast & Geodetic Survey and track down more than a dozen “benchmarks” within a few miles of our home. They were often located in areas heavily wooded areas so many yards from a tree with a triangular blaze cut into it.

    • francis eugene 'gene' pratt says:

      Do you know how they cut the triangular marker? In my Baytown, TX, area survey marks were (at least sometimes) indicated by 3 parallel slashes on the side of trees nearest the survey line. A slash would be easier and faster than a triangle.

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