| Re: vector layer comparison in IDL [message #42809 is a reply to message #42764] |
Wed, 23 February 2005 12:06   |
Mark Hadfield
Messages: 783
Registered: May 1995
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Senior Member |
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yp wrote:
> Mark Hadfield wrote:
>
>> yp wrote:
>>
>>> Is there a sensible way to compare two exported vector layers
>>> and compute the residuals using IDL? I am sorry for asking this
>>> simple question...
>>
>> Not at all. I, for one, have no idea what your simple question
>>means. Is this some sort of GIS thing?
>
> Yes Mark, it is related to GIS. Then, you might advise to use some
> GIS package. However, I have have 100s of *files* - these files are
> basically ARC vector layers exported as ASCII files (lon, lat, ...,
> attributes). For instance, I have 50 sites where the surveys have
> been done in two different times (hence 100 ASCII tables); estimate
> the absolute changes (residuals or differences). I believe that there
> should be some way of doing it in IDL...
OK, so what do *you* think is the way to go about this and where do you
foresee difficulties? Can you get the data into IDL? Do the lon and lat
data differ between 2 surveys at the same site? If not, simple
subtraction of the attribute data should be OK; if so, I guess you'll
need to interpolate to a common grid first. Or is there more to it?
--
Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)
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