Hei Arnd,
now, the background-layer option includes
a) delimiting the used points to those that are inside the backgound polygon
b) is clipping the thiessen polygons to the borders of the backgound
polygon.
I hope that is what you needed. The dealing with regular point
configurations is still an issue though.
Stefan
Stefan Steiniger schrieb:
Hei Arnd,
I just had a look on the point data set you sent me.
The problem is that the point positions are partly regular. In effect it
is difficult to test/be conform to the Delauney constraints (circle
condition). The currently used simplex-insert algorithm obviously can't
handle such configurations, i.e. does not know which triangle to split
for the new point to insert, as the point is lying on a triangle edge.
The only choice here is to use a different algorithm (the old Pirol
one?, or I re-implement one which I already have - the latter needs to
be done for copyright reasons and it both takes time, as the
thiessen-line generation needs to be implemented newly.. not sure when I
find the time). The other solution would be to move all the points
slightly to avoid that they are located on the connection lines/regular
grid. However, this doesn't make sense from a GIS perspective. Or I
would find a way to modify the current code, i.e. change the point-pos
and remove the point aferwards. But again - I am not so savy on that
computational geometry stuff as I haven't implemented that algorith.
:(
on the clipping... I plan to work on that soon.
stefan
Arnd Kielhorn schrieb:
Hi Stefan,
I want that the background layer bounding the Thiessen Polygons. It
would be great!
Kindly regards
Arnd
Stefan Steiniger schrieb:
b) i need to check problem C, but I am not sure if there is a
misunderstanding. The background-border-layer is only used to
determine the dimensions of the final output (i.e. to avoid having a
too small output). Not sure if this is what you thought?
Arnd: I thought that the background border layer should avoid that the
outer polygon (cells) of the resulting output getting to big. I try to
use this function to delimit the output with a border layer (e.g. a
border of a field => polygon).
question: so you would like to have excluded the points outside that
backgound polygon? or do you want that the background polygon is
bounding the thiessen polygons? That could be possible to do as an
additional intersection operation (maybe)
and thanx ;)
Stefan
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