Columbus supports keywords that allow you to scale standard deviations for each
observation type. When one of the following keywords is encountered, the 
observation standard deviation it applies to is scaled on Import or when 
using Adjust From File.



Example:

! Scale all the standard deviations for chord distances by 1.5 when they are loaded from 
! the file.
_S_CHORD_SD; 1.5

! This will apply to any chord distances that are below (this keyword) in the file.

! Turn the scaling off (for all chord distances that follow), set _S_CHORD_SD to 1.0.
_S_CHORD_SD; 1.0



NOTE:

Some scalars are actually applied to the observation set covariance matrix (not the 
standard deviation). Applying a scalar to a covariance matrix is different than applying a 
scalar to a standard deviation.

If you apply a scalar of 2.0 to a covariance matrix, that is equivalent to applying a scalar 
or 1.4142 to a standard deviation.

The easiest way to apply the same scalar to all observations is to use the keyword 
_ADJUST_APRIORI_FACTOR. This is applied at adjust time (not during import or file loading).

Following is how to apply the equivalent scalar to a GPS covariance matrix and to chord distance 
standard deviation:


Example 1: 

! Desired covariance scalar is 4.0
_S_XYZ_COV; 4.0
! Now the square root of 4.0 is 2.0, so use that for the standard deviation scalar.
_S_CHORD_SD; 2.0



Example 2: 

! Desired standard deviation scalar is 3.0
_S_CHORD_SD; 3.0
! Now the square of 3.0 is 9.0, so use that for the covariance matrix scalar.
_S_XYZ_COV; 9.0




! Scale azimuth standard deviations when loaded from the file.
_S_AZ_SD; 1.3



! Scale direction standard deviations when loaded from the file.
_S_DIR_SD; 1.3



! Scale bearing standard deviations when loaded from the file.
_S_BEAR_SD; 1.3



! Scale horizontal angle standard deviations when loaded from the file.
_S_HA_SD; 1.3



! Scale zenith standard deviations when loaded from the file.
_S_ZEN_SD; 1.3



! Scale chord (slope distance) standard deviations when loaded from the file.
_S_CHORD_SD; 1.5



! Scale horizontal distance standard deviations when loaded from the file.
_S_HOR_DIST_SD; 1.5



! Scale height difference standard deviations when loaded from the file.
_S_HGTDIFF_SD; 1.5



! Scale delta north standard deviations when loaded from the file.
_S_DN_SD; 1.5



! Scale delta east standard deviations when loaded from the file.
_S_DE_SD; 1.5



! Scale delta up deviations when loaded from the file.
_S_DUP_SD; 1.5



! Scale geodesic azimuth standard deviations when loaded from the file.
_S_GEODESIC_AZ_SD; 1.7



! Scale geodesic distance standard deviations when loaded from the file.
_S_GEODESIC_SD; 1.7



! Scale latitude standard deviations when loaded from the file. Only applies
! to latitude coords defined using the _OBS_LAT keyword.
_S_LAT_SD; 2.5



! Scale longitude standard deviations when loaded from the file. Only applies
! to longitude coords defined using the _OBS_LON keyword.
_S_LON_SD; 2.5



! Scale height standard deviations when loaded from the file. Only applies
! to hgt coords defined using the _OBS_HGT keyword.
_S_HGT_SD; 2.5



! Scale north standard deviations when loaded from the file. Only applies
! to north coords defined using the _OBS_NORTH keyword.
_S_NORTH_SD; 2.5



! Scale east standard deviations when loaded from the file. Only applies
! to east coords defined using the _OBS_EAST keyword.
_S_EAST_SD; 2.5



! Scale GPS covariance matrix when loaded from the file.
_S_XYZ_COV; 2.0



! Scale lat, lon, hgt covariance matrix when loaded from the file.
_S_LLH_COV; 2.0



! Scale north, east, hgt covariance matrix when loaded from the file.
_S_NEH_COV; 2.0