Estimate of Survey Positional Error

[Imperial College Caving Club]

Hi Survex users,

We're trying to connect two large cave systems on our expedition in
Slovenia this summer. To aid this, it would be very useful to have a
best estimate of error in our survey, in particular the relative
position of those two 'closest approach' stations in either cave. Of
course, we have an approximate error from our loop closures, but we
are wondering whether something with more mathematical sophistication
might give a better grasp.

I believe that survex samples the error from the loop closure, and
then distributes this according to an estimate for
tape/compass/clino/positional error:

http://csg.bcra.org.uk/surveynotes.html

Is there anyway of getting at this information directly? If we had an
estimate for these factors, then we should be able to use the above
linked formulae (which basically just project the errors from various
instruments into a Cartesian positional error) along the (unclosed)
loop to arrive at a suggested distribution of error in x,y,z.

What would be absolutely beautiful would be a mode for Aven to display
ellipsoids of position error at every shot location, at which point
one could physically visualise the absolute error increasing through
the graph away from the fixed position(s), being reduced by the loop
closures, etc.

Best,

Jarvist

-- 
Imperial College Caving Club
http://union.ic.ac.uk/rcc/caving
ic.caving [AT] gmail.com