The points and observations section is bounded by the pair tag
<points-observations> and contains information about points,
observed horizontal directions, angles, and horizontal distances, height
differences, slope distances, zenith angles, observed vectors and
Optional attributes of the start tag
for the definition of default values of standard deviations
corresponding to observed directions, angles, and distances.
direction-stdev = "..."defines the implicit value of observed direction (default value is not defined)
angle-stdev = "..."defines the implicit value of observed angle (default value is not defined)
zenith-angle-stdev = "..."defines the implicit value of observed zenith angle (default value is not defined)
distance-stdev = "..."defines the implicit value of observed horizontal distance (default value is not defined)
Implicit values of standard deviations for the observed distances are calculated from the model with three constants a, b, and c according to the formula
where a is a constant part of the model and D is the observed distance in kilometres. If the constants b and/or c are not given, default values b=0 and c=1 will be used.
<points-observations direction-stdev = "10" distance-stdev = "5 3 1" > <!-- ... points and observation data ... --> </points-observations>