height of light?

[+infosponge]

On this detail, and many others around here I see a reference to "height of light above station mark is ...".

http://www.geocaching.com/mark/details.asp?PID=AG1022

Any idea what this means? Is this some kind of indication of how unobstructed the location is? Surveyor-speak for something else?

[+pater47]

is that the light on the light pole is one meter above where the marker is set.

 

Ever notice everybody is willing to give THEIR 2 cents worth but only offer a penny for YOUR thoughts?

[+infosponge]

That's what I thought at first, but it's only one meter high? That's not much of a light pole!

I think it must be referring to something else.

[+infosponge]

That's what I thought at first, but it's only one meter high? That's not much of a light pole!

I think it must be referring to something else.

[+pater47]

Well, according to the name, the light is there for turtles.

 

Ever notice everybody is willing to give THEIR 2 cents worth but only offer a penny for YOUR thoughts?

[+pater47]

Well, according to the name, the light is there for turtles.

 

Ever notice everybody is willing to give THEIR 2 cents worth but only offer a penny for YOUR thoughts?

[+LazyK]

Maybe the marker is imbedded in the pole (several feet off of the ground) and is one meter below the light.

[+Klemmer]

Just having read a situation that is clearer (I'll post the link if I can find it again), here's my 2 cents worth:

The way I read these is that they are talking about the height of the REFERENCE (in this case Turtle) above the benchmark in question. Probably done with classic surveying methods (transit sight & trig calculations).

[survey tech]

Hello everyone, Im here to promote, and to thank you for, your interest in Land Surveying.

 

Lights were frequently used as targets for surveying observations at night. The work was done at night to avoid the effects of heat wave distortion over long distances which made obsevations taken during the day less accurate. In many cases the lights were mounted on towers, up to about 10 meters high in order to be visible above trees, buildings and other obstacles. In fact the surveyor, with his instrument, was often set up in a tower as well, to get above the obstacles. This was neccessary only in relatively flat areas. In hilly or mountainous areas, the highest possible locations for the markers were selected in order to avoid the need for towers. In many remote places, where little or no development of the land has occured, the remains of the old wooden towers are still there to be seen, decaying into ruins. Later, collapsible modular metal towers came into use, which were assembled and disassembled on site, then transported and reused.

 

For more information on Land Surveying, please feel free to visit rpls.com, and ask any questions you may have.

[+parkrrrr]

quote:

---

Originally posted by survey tech:

In many cases the lights were mounted on towers, up to about 10 meters high in order to be visible above trees, buildings and other obstacles.

---

 

Only ten meters? Check out the longer 1946 note for Bouries.

 

[survey tech]

To my knowledge, 10 meters was generally considered the limit for purposes of safety and stability, but in unusual cases higher towers may have been needed.

[+parkrrrr]

It occurred to me this morning that a light 34 meters high was probably not really 34 meters high, but 34 feet. I'm sure something got lost in the translation.

 

[Circum]

...move to top of list.

[DaveD]

A 34 meter (110-120 ft) light was very common in triangulation (I spent many nights up there). The lights or signals were collimated on top of the observation tower directly over the observer. A 1 meter light would be set or posted over a stable wooden observing stand built directly overy the survey monument. The light would be removed when the station was occupied for trianuglation observations with the theodolite. If you go to the NGS web site and look under "Our History", you can find many images of historical triangulation. You can also find details of this process in Coast & Geodetic Survey Special Publication 247 "Manual Of Triangulation."

[Wild T2]

One of the pics from the site DaveD mentioned.

http://www.photolib.noaa.gov/historic/c&gs/theb1638.htm