With some distance measurements there may be a possibility of an undefined scale error in the measurements. For example one instrument may be suspected of introducing a scale error to all observations made with it. SNAP can apply a correction for scale errors to blocks of distance data. This is done in a similar manner to the way that refraction corrections are applied to zenith distance data.
Each scale error that you want to apply is given a name. In the data files you can associate a name with a group of distance measurements.
You can assign values to each scale error, and you can use SNAP to calculate best fitting values if you wish.
The scale errors are always expressed as a part per million error.