Observed angles are expressed with the following attributes of an
empty-element tag <angle />
from = "..." standpoint identification (optional)
bs = "..." backsight target identification
fs = "..." foresight target identification
val = "..." observed angle; see Angular units
stdev = "..." standard deviation (optional)
from_dh = "..." instrument height (optional)
bs_dh = "..." backsight reflector/target height (optional)
fs_dh = "..." foresight reflector/target height (optional)
Similar to distance observations, one observation set may group angles observed from several standpoints.
<angle from="433" bs="422" fs="402" val="128.6548" stdev="14.1"/>
<angle from="433" bs="422" fs="402" val="128.6548" />
<angle bs="422" fs="402" val="128.6548" stdev="14.1"/>
<angle bs="422" fs="402" val="128.6548"/>