Note: This addon document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade your GRASS GIS installation, and read the current addon manual page.
The transformation equations are computed anew for each iteration. The GCP with the largest distance between the computed coordinates and the actual coordinates is deactivated and the next iteration is started. Filtering stops when the overall RMS error is below the given threshold or when the number of active GCPs is equal to the required minimum number of points or when the optional maximum number of iterations (option iterations) has been reached. With the -d flag, the largest GCP error is used instead of the overall RMS error.
m.gcp.filter uses by default the results of forward transformations (source to target) for filtering. With the -b flag, the results of backward transformations (target to source) are used.
The status of GCPs (active / inactive) is only updated with the -u flag. GCPs that have been filtered out will be deactivated, not deleted.
The transformations are:
order=1:
e = [E0 E1][1].[1] [E2 0][e] [n] n = [N0 N1][1].[1] [N2 0][e] [n]
e = [E0 E1 E3][1 ] [1 ] [E2 E4 0][e ].[n ] [E5 0 0][e²] [n²] n = [N0 N1 N3][1 ] [1 ] [N2 N4 0][e ].[n ] [N5 0 0][e²] [n²]
e = [E0 E1 E3 E6][1 ] [1 ] [E2 E4 E7 0][e ].[n ] [E5 E8 0 0][e²] [n²] [E9 0 0 0][e³] [n³] n = [N0 N1 N3 N6][1 ] [1 ] [N2 N4 N7 0][e ].[n ] [N5 N8 0 0][e²] [n²] [N9 0 0 0][e³] [n³]
In other words, order=1 and order=2 are equivalent to order=3 with the higher coefficients equal to zero.
Available at: m.gcp.filter source code (history)
Latest change: Mon Jun 28 07:54:09 2021 in commit: 1cfc0af029a35a5d6c7dae5ca7204d0eb85dbc55
Note: This addon document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade your GRASS GIS installation, and read the current addon manual page.
Main index | Miscellaneous index | Topics index | Keywords index | Graphical index | Full index
© 2003-2023 GRASS Development Team, GRASS GIS 7.8.8dev Reference Manual