[UW-GIS-L] random errors
crossco at u.washington.edu
Thu May 31 13:05:41 PDT 2007
In my first large-scale GIS effort, I am encountering some errors for
which I cannot pinpoint the cause.
I am using the "buffer" and "erase" functions in sequence and repeating
it many times; specifically, I am buffering a stream vector with some
width, and then again with a width incrementally larger, and then erase
the smaller buffer from the larger, leaving a rectangular "buffer" some
distance from the stream vector.
For example, I buffer the stream vector with a 10ft wide buffer, and
then again with a 20ft wide buffer. I then erase the inner 10ft of the
20ft buffer - leaving a 10ft wide buffer that is 10ft from the stream
vector. I then repeat this with 30ft and 20ft, moving away from the
stream vector in 10ft increments. I do this until some decision
criteria are met (based on a zonal stats raster analysis). this is being
repeated many times for each stream vector segment, and across many
(tens of thousands) vector segments.
My problem is that the process is encountering an error in the buffering
and/or erasing process and quitting even though the decision criteria is
met. However, if I restart the process from the point where it quit,
there appears to be no problem, and it will go to completion. The
result is a seemingly random error in the buffering and erasing
functions. Has anyone else encountered this? any suggestions?
I am taking care to conserve memory, and storing intermediate buffers
"in memory" and deleting after iterations, so I don't see a memory drain
on the system.
Thanks for any suggestions.
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