Cave-Surveying digest, Vol 1 #62 - 2 msgs

[Patricia N Kambesis]

A comment on Garry Petrie's question on backsites and how it should be
done.

If two different people are using two different instruments, its
important that both of those instruments be calibrated on some sort of
predefined compass course.  At the very least the two instruments'
readings should be compared before the onset of the survey to determine
if there are any discrepancies in the instrument readings.  It is not
uncommon for two different suunto compasses or clino's to differ in their
readings sometimes as much as several degrees.  

In order to minimize human error its always best to record the readings
uncorrected.  And the data recorder should compare the back and front
sites to make sure they agree to whatever the established standard of the
project or the survey.  I've seen data where backsites were taken but
never compared to the frontsite - apparently the data keeper
misunderstood and thought that the very act of taking the backsite was
quality control in and of itself. 

Pat K.