| rextrap | stsdas.hst_calib.foc.focgeom | rextrap |
rextrap -- Extrapolate a reseau grid.
rextrap inres entry outres
This task extrapolates a reseau grid, extending it by one row or column on any or all sides. Along an edge, each extrapolated reseau point is obtained in the following manner. A 2 x 3 rectangle of reseau points within the original grid is taken, with the long axis parallel to the side. A plane is fit to these six points, ignoring those that are INDEF, and the linear fit is evaluated to obtain one extrapolated point. At a corner, the fit is also evaluated at a second point so that the extrapolated points fill the entire edge except for the corner. The corner point is then obtained by fitting a plane to the 2 x 2 set of reseau points at the corner of the original grid plus four extrapolated points, two on each side. The input reseau table may contain as small a grid as 2 x 2. For a small reseau grid, the fit is made to all the points in the table, and then that fit is evaluated to obtain all of the extrapolated points.
Note that this results in a larger reseau grid, so it will not be possible to compare the input and output grids with, for example, the rdifferx or rstat tasks, or to combine them with rappendx. The "tracking" is updated with the letter E.
This task was written by Phil Hodge.
The rmarkerx task is useful for moving reseau marks.
Type "help focgeom option=sys" for a higher-level description of the focgeom package.
