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2.1 Angular units

Horizontal angles, directions and zenith angles in gama-local XML adjustment input are implicitly given in gons and their standard deviations and/or variances in centicentigons. Gon, also called centesimal grade and Neugrad (German for new grad), is 1/400-th of the circumference. For example

 
 <direction  from="202" to="416" val="63.9347"  stdev="10.0" />

The same angular value (direction) can be expressed in degrees (sexagesimal graduation) as

 
 <direction  from="202" to="416" val="57-32-28.428"  stdev="3.24" />

In XML adjustment input degrees are coded as a single string, where degrees (57), minutes (32) and seconds (28.428) are separated by dashes (-) with optional leading sign. Spaces are not allowed inside the string. Gons and degrees may be mixed in a single XML document but one should be careful to supply the information on standard deviations and/or covariances in the proper corresponding units.

Sexagesimal seconds (ss) are commonly called arcseconds, they are related to the metric system centicentigons (cc) as

ss = cc/400/100/100 * 360*60*60 = cc*0.324.

Internally gama-local works with gons but output can be transformed to degrees using the option --angular 360.

Another angular unit commonly used in surveying is the milligon (mgon), 1 mgon = 1 gon/1000 (similarly as 1 mm = 1 m/1000) and 1 cc = 10 mgon.


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