What is HEIGHT OF LIGHT ?

[+David]

"HEIGHT OF LIGHT ABOVE STATION MARK 2 METERS"

 

I've seen this phrase in several descriptions, usually triangulation stations. What does it mean?

[+Black Dog Trackers]

Here is a previous thread on that question, and at the bottom is a link to an even earlier thread. Some interesting surveying history there.

[+David]

Thanks for the links, I should have searched first. Quite interesting indeed.

[Z15]

The light is the target which the surveyors sighted upon and it was usually the highest point on the towers.

 

Triangulation was done at night because there was better visibilibty and that produced less errors cause by daytime heat etc. Also it afforded the tower building party's the days to build the towers, the survey party worked the nights and then they took them down the next day and move them to another site for the next night.

btw-It only took then a few hours to erect the towers.

[+strfry]

quote:

---

Originally posted by Black Dog Trackers:

Here is a previous thread on that question, and at the bottom is a link to an even earlier thread.

---

Since all historical links are now broken and search only seems to go back go January, can you recap?

[+Black Dog Trackers]

Here is the link. Temporary Bilby towers were erected at the site. After dark, a light on the tower would serve as a sighting target from distant stations.

[Z15]

There is lots of info on the NGS site on this but there is a book called Manual of Geodetic Triangulation that has much more detail. It was the bible the crews used in the field. Its C&GS Special Publication 247. Manual of geodetic triangulation by Gossett, Franklin R., January 1950, 344 p., $25.00 available from NGS for purchase.

 

NGS distributes some of these

publications as a consigned sales agent of the U.S. Government

Printing Office. Publications in this booklet may be ordered,

prepaid by personal check or money order ( payable to DOC/NOAA),

or by VISA, MasterCard, Discover or American Express from the:

National Geodetic Information Branch

N/CG174, SSMC3 Room 9202

National Geodetic Survey, NOAA

Silver Spring, MD 20910

Telephone: 1-301-713-3242; Fax Telephone: 1-301-713-4172

Office Hours: 8:00am -4:30pm EST

 

Link to all publications

 

Many old photo's of the crews in action, the equipment and the procedures to follow. Some of the photo's are on the NGS historical site but its very few.

 

Also some years back, Professional Surveyor Magazine had a story with photo's of the Coast and Geodetic Survey triangulation party doing a survey in the midwest. I have looked long and hard for my copy but cannnot locate it anymore. It was within the last 5 yrs.

 

[This message was edited by elcamino on April 01, 2003 at 05:33 AM.]