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monkeykat

HEIGHT OF LIGHT ABOVE STATION MARK

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On several benchmark datasheets for my area I have seen the text "HEIGHT OF LIGHT ABOVE STATION MARK..." listed as the last item in the description. Does anyone know what this refers to? Here are a couple examples:

 

OF2498 - Gotta love the "find" on this one, but to each his own...

 

and

 

OF2312

 

I originally noticed the text when searching for OF2312, and figured it referenced a parking lot light. Now after reading it again, I am not so sure. 30 meters seems pretty high for a parking lot light. In fact, i can't remember if the parking lot even had lights in it. But it may be possible though.

 

Does it refer to some other light source, or something to do with time of day and measuring heights using the angle of elevation and trigonometry? Also, on the data sheets I noticed the phrase is always the last item of the description. I find it hard to believe that the mark with a "light" over it is always the last disk listed.

 

Any insight? Thanks.

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Hi monkeykat -

 

This height is the height above the station that a light was set at so the position of the station could be observed from other stations, some of them perhaps miles away. Here is a previous topic on this question. (If you put +height + light in the forum search window, after clicking "search" near the top of the page, you will get this article and others too.)

 

The height of light subject is an interesting topic on the history of surveying, with bilby towers, etc. <_<

 

The tower for the light was a temporary tower - a sort of kit that traveled around and was built at various places for observation.

Edited by Black Dog Trackers

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Thanks for the info. You know I did a search, but not well enough apparently. When I tried the search again after a few tries I found no fewer than 8 previous threads on this topic. Gotta do better with my searches. And I'm a software engineer too! Argh, how embarrassing.

 

Love that photo too.

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