Snap is the main program in the snap package. It performs a least squares adjustment of coordinates to best fit survey data.
The adjustment is defined in a command file. This in turn defines a station coordinate file containing the names and coordinates of the fixed and adjusted stations, and one or more data files containing the observations used to calculate the new station coordinates.
The two principal outputs of the adjustment are a listing file (command_file.lst) containing a textual report of the adjustment, and a binary file (command_file.bin) which may be viewed with the snapplot program to analyse the results.
If the adjustment is unable to run then snap will also generate an error file (command_file.err).
There is also a "windows" version of snap, snapadjust, which differs only that it displays its progress in a window rather than in the DOS window.
Snap is most conveniently run from the snap_manager program, but it can be run directly from a DOS prompt using the command:
SNAP [options] command_file
where
command_file |
is the name of the command file defining the adjustment. Snap uses default extension ".snp" for this file if none is specified. |
Two options may be specified when starting SNAP. These are
-c config_file |
Specifies a configuration file that snap will use for configuration settings before processing the command file. |
-u user_directory |
Defines the user directory in which SNAP will look for default or user specified configuration files |
-t number_of_threads |
Enables the use of multi-threading in matrix routines. number_of_threads can be either 0 (single threaded routines), a number of threads to use, or "auto" to allow snap to choose the number of threads |
-z |
Disables calculation of the inverse normal equations and sets the inverse to zero. This allows much more rapid solution of large adjustments for calculating coordinates and testing for gross residuals, but means that statistics are not correct |