#163: g.transform no longer calculating error for 2nd order transformation -----------------------+---------------------------------------------------- Reporter: cmbarton | Owner: [email protected] Type: defect | Status: reopened Priority: major | Milestone: 6.4.0 Component: default | Version: svn-develbranch6 Resolution: | Keywords: g.transform georectify Platform: All | Cpu: Unspecified -----------------------+---------------------------------------------------- Changes (by hamish):
* status: closed => reopened * resolution: fixed => Comment: > It turns out that 2nd order transformation need MORE than 6 points, not 6 points > or more Not according to the i.rectify man page, "The number of control points required for a selected order of transformation (represented by n) is ((n + 1) * (n + 2) / 2) or 3, 6, and 10 respectively." And imagery/i.vpoints/analyze.c's compute_transformation() which leads to imagery/i.vpoints/crs.c's calccoef() function agrees. n >= 6. The same code is reused by g.transform, I assume they are identical after re-indent. no idea about what the needs of backtransforming are. I assume they are symetric with a forward transform. No idea if any of this matters to the status this bug. Reopening as the reason for closing it is invalid and the interactive georectify modules now need to be reverted. Hamish -- Ticket URL: <http://trac.osgeo.org/grass/ticket/163#comment:3> GRASS GIS <http://grass.osgeo.org>
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