Backsights (and lava caves)

[P A Hill & E V Goodall]

Bill Frantz wrote:
> My current idea for a true solution to this problem is a new instrument.
> It would hold two laser pointers, and sit on the station.  (Short tripods
> might be used as stations with this method.  You would align one laser on
> the previous station, and the other on the next and read the turn angle off
> the instrument.  With 3 tripods, two reflectors, and the instrument the
> survey would proceed by:

Sort of a related to the old plane table survey technique.
see
https://secure.surveysupply.co.uk/products/prods2/alidade/plaintab.htm
For a brief history see:
http://www.pobonline.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2338,9496,00.html

 From what I understand (which isn't much) is that today, you'll still 
plane plane table surveys when surveying a 'site', maybe for creating a bit 
of detailed togography for a geological, hydrological or even an 
archeological study.  One person stays at the table turning angles and 
shooting to one or more others who walk about on the site picking 
interesting points, thus creating a detailed map of the visible site.

As the 2nd of the above URLs says: "The U.S. Army Corps of Engineers was a 
great proponent of the plane table, using them to map engineering project 
surveys and many military bases."

-Paul