Paul Fisher , Apr 13, 2002; 12:16 a.m.
My information may be well out of date here, but when I did a bit of surveying as a side-line many years ago, the tripod was very different from a photographic tripod. Basically there is no facility at all for pan or tilt. The top of the tripod is a flat plate with a large diameter hole and a captive bolt on a hinged bracket. The bolt goes into the tri-brach of the instrument which sits down flat on the plate. By loosening the bolt you have some lateral movement, which is used to position the instrument dead centre over a survey mark (the bolt is hollow, so you can use a right-angle finder built into the instrument to sight through it). The instrument's tri-brach has three levelling screws.
Trying to convert this system to photography would not be a trivial task. However the leg sets are built to last and take a real hammering on construction sites etc. Most of the ones I've seen use a two-part upper leg with a solid lower leg that slides up between the two upper parts. There is a clamp at the lower end of the upper leg which allows the lower leg to be locked in place at any extension. (Got that?)
Hope this helps