| Re: vector layer comparison in IDL [message #42764 is a reply to message #42751] |
Fri, 25 February 2005 06:35   |
yp
Messages: 42
Registered: February 2005
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Member |
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Mark Hadfield wrote:
> 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)
Hi Mark,
Thanks for your suggestion. I did think of the same; to bring both
layers to same grid. But I am stuck here... How should I go about
interpolating the (x,y) pairs (No attributes are taken into account at
the moment)? Here I have to interpolate the co-ordinate rather than
data. If I go like interpolating all y's f(x) and all x's f(y) I'll end
up with wrong interpolated data when there are more than one parallel
lines.
Any clue?
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