Horizontal angle observations (HA)

Horizontal angles (HA) are entered as a set of directions observed from one station to a number of other stations.

The angles are expressed in degrees, minutes, and seconds. SNAP supports two formats for angle data

• as three numbers (e.g. 123 45 06.7)
  
  
• as a single number following the convention adopted by HP calculators (e.g. 123.45067).
• as decimal degrees (e.g. 123.75186).

The format used in input files is defined by the #hp_angles, #deg_angles, and #dms_angles data definition commands.

The errors of angles in input files are expressed in seconds, or in degrees if the #deg_angles format is used.

In the SNAP output listing the residual are expressed in seconds. You may also show the residual as a distance. This is the minimum distance that the target would have to be moved to make the observed direction exactly correct.

See also

Observation file overview

Summary of data types

Observation file format

Azimuth data

Projection bearing data

The #data command

The #ha_error command

The #hp_angles, #deg_angles, and #dms_angles commands