v.proj, grid overlays may be wrong

[Simon Cox]

(i)  try using g.setproj to fix the PROJ_INFO files up in the troublesome
location

(ii)  an issue related to both of the topics in the Subject - people may
have noticed that when you use v.proj to move simple, straight lines from
one location to another (eg a graticule set up using v.mkgrid) the lines
stay straight in the destination location, whereas (if it is in a different
projection) they should be curved.  This is because v.proj only operates on
nodes and points.  Thus, if you have a line defined only by its two end
points (which is how v.mkgrid works for each segment) then only these two
points are transformed.  This means that the middle of the line, which is a
simple chord, will pass over the wrong bit of country.  I found this
frustrating.

To correct this, I wrote a program (actually a script) which I called
"v.plant" (since it is the complement of v.prune) to fill in extra points
if the original spacing is too great.  Thus you can turn a two-point line
into an N-point line where N can be large!  This should be run in the
original location _before_ running v.proj in the new location.

I put v.plant on moon a couple of weeks ago (I think it should be in
"outgoing") but have had no feedback since.  Perhaps no-one else has come
across or recognised the problem?  Perhaps I did not describe it properly!


Simon Cox

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Dr Simon Cox                          __  \
CSIRO Exploration & Mining         ,~'  L_|\    Australian
39 Fairway, PO Box 437,         ;-'         \   Geodynamics
Nedlands, WA  6009  Australia   (            \  Cooperative
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s.cox at dem.csiro.au                         7
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