I have a customer here in Oregon looking for a Plane Table. He has an Alidade already. Does any one have one they would like to sell?
Wayne Harris once had several, I used them, contact the Umatilla County Surveyor, might know what happened to that stuff, he bought Wayne's records for the County Surveyors office, had a lot of old info not found anywhere else. You probably know Dave already.
jud
Does anyone know how surveyors were able to do large scale mapping with those things? I have heard that a lot of the early quad maps were mapped with a plane table and alidade. I can see how you could map a small project using stadia, but how would you map an entire quad with one that wouldn't take forever?
The Bow Tie Surveyor.
There is one on eBay right now:
Jeff
I have a plane table and tripod I would be willing to sell. I also have an old Gurley alidade.
Mapping large areas is simply mapping a whole bunch of small areas and piecing them together. To match the area covered on one plane table sheet to adjacent sheets, you shoot & plot some common points that fall near the edges. Could be just control points, but usually you would try to find 1 or 2 features that you could identify fairly precisely - a corner of a structure or a particular tree.
The US Engineering Department (predecessor to the USACE) mapped many of California's rivers in the early 1900s with plane table. These were corridors 1/2 mile to 1-1/2 mile wide centered on the river, and anywhere from a few miles long to over 200 miles long.
There are a few errors in the mapping here and there - the result of maybe someone bumping the table & rotating it off the backsight orientation, or blown distance reading/reduction. But overall, the work was pretty detailed and pretty good.
A bit more labor intensive, but the working drawing on the table provided a great visual check to the crew for completeness and general accuracy. A good plane table crew could provide better field info and produce a better mapping product than many companies can today using a total station with data collector, and CAD.