[Therion] Surveys without centrelines

[Stelios Zacharias]

Dear all,

Can Therion put together scraps on the basis of the polygonal system of 
survey? (I think this is what it is called - it uses as set of triangles 
and only distance measurement rather than the distance, azimuth, slope 
measurements we are used to).

A friend has a survey constructed with only distances taken from two 
points (and successive points) so as to create a flat area of triangles 
(it is flat because the "floor" is the sea and the water level is 
constant). There is therefore no centreline, but a series of points, 
each joined by two measurements to other points and all coming back to a 
known baseline. In the days of paper survey, the plan would be drawn 
with just a compass from one point to the next, beginning off the baseline.

There exist a series of drawings of the cave, but on separate sheets of 
A3 paper, which could be digitised but they will need some way to be 
joined together (with errors shared from sheet to sheet), hence my 
question. Currently they do not join in a satisfactory way when the same 
stations are aligned from one sheet to the other.

In a worst case scenario, I would imagine using trigonometry to create a 
centreline around the outside edge of the polygons, but if there is a 
simpler way, I would be glad to know it.

Cheers,
Stelios

PS is this method called the polygonal method, or am I misremembering?