30 foot signal tower.

[+WildwoodBob]

A benchmark that was last recovered in 1934 has this note: "THERE IS A 30-FOOT WOODEN SIGNAL HERE WHICH WILL BE LEFT STANDING AS IT WILL ENDURE WEATHER AND BE USEFUL FOR FUTURE SURVEYS."

 

The area has changed significantly since 1934. The directions to the location don't exist, etc. The only reference point is the "3rd knoll on the ridge." The coordinates lead to a flat area, near a few knolls, but hard to tell what they meant as the 3rd knoll, as the trail used no longer exists. The area is heavily overgrown with mature trees and thick underbrush, so finding the remains of this tower may be my only clue.

 

I have 3 questions. First, what would this signal tower have been made from? Cut trees? What shape might it have been in? And would the engineers have built it over the station mark?

 

Thanks in advance for any assistance.

[survey tech]

Yes, it would probably still be directly over the point. I have found several points over the years with tower remains around them, especially in the mountains and the desert. Check out the pictorial gallery of USC&GS history on the NOAA website, they have some pictures of both the early wooden towers and the later metal ones.

[TeeGate]

I can only surmise it was easier in remote locations to build the towers from wood and leave them there. If the area was not remote, a Bilby tower was used for triangulation stations. It was named after the designer, Jasper Bilby. They were a tower within of a tower, usually made of metal. When you see a PID that mentions for example, "A 100 foot tower will clear all obstacles", it is talking about a Bilby tower. Obstacles near the location, or the distance between towers, determined how high the tower had to be. The inner tower provided an undisturbed instrument platform, while the outer tower was what the men climbed. Usually a team of men would construct it, and wait for dark on a clear night.

 

They would climb the tower and set a light at the peak, so that all towers in the area could see it. They would then perform whatever was needed to align their equipment for the monumenting of their triangulation station. These are the benchmarks with the triangle on them. They then would usually monument two reference stations at some distance away with arrows on them pointing toward the tips of the triangle on the station benchmark. I have found many that did not point at the tips of the triangle, so that is not always the case. They would sometimes monument an Azimuth mark, usually quite a distance from the station. I believe this mark was in alignment with the North Star. Many of the Azimuth marks are usually destroyed because they are so far from the relative safety of the immediate area around the stations. Also, some people who I have contacted who used a Bilby tower in the past, say that the station was monumented first, and the tower placed over it. So apparently that is up for discussion.

 

Guy

[+WildwoodBob]

quote:

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Originally posted by survey tech:

Yes, it would probably still be directly over the point. I have found several points over the years with tower remains around them, especially in the mountains and the desert. Check out the pictorial gallery of USC&GS history on the NOAA website, they have some pictures of both the early wooden towers and the later metal ones.

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Cool site. If anything is left of a 30 foot tower after 68 years, I should be able to find it! I did find some old logs laying on the ground, forming a triangle. Not sure if this could be leftovers or not. I didn't have any digging utensils along, and the dirt inside the triangle was pretty deep.

[+GEO*Trailblazer 1]

I have found several of the older towers here in Mo. the timbers are gone but the concrete and steel legs still remain. remember after all these years stuff can get thick with udergrowth fast especially when the area used to be kept cleared. I found one recently that has a brass cap with 1942 date, GF0895, GF0984, GF0903, and to meters ref. GF0896, newer.