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Thank you to all who offered suggestions re the 'unformed' polygons problem.
The problem was eventually resolved by installing the newest version of
POLYVEC.exe (apparently not included in the latest service pack), which was
sent to me by a staff member at Clark Labs.
The customer service provided by the staffer who helped me with the problem
was excellent.
Regards,
Les McNamara
University of Western Sydney
----- Original Message -----
From: Les McNamara <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, May 15, 2001 11:51 AM
Subject: Idrisi-L : POLYVEC fails to form polygons
> --- Start of Idrisi List message
> Dear all,
>
> I am trying to create a vector file of a 25Mb raster landuse image so that
I
> may link landuse to a database. The image contains 30 different landuse
> types. I am using Idrisi32 with the latest update on a Windows 98 machine.
> The area of interest (a watershed) is surrounded by pixels with a value of
> zero - ie the backround.
>
> POLYVEC successfully converts the image to a vector layer, however two
> contiguous (different values) landuse areas in the raster image are not
> converted into polygons. All other contiguous areas that share the same
> value are displayed correctly. The area of the 'unformed' polygons in the
> new vector layer is identified correctly when clicked on within Idrisi32
but
> the area does not highlight. One of these areas appears to be 'open' to
the
> backround value (ie there is no line separating the background and the
> landuse, even though the boundary is clearly defined in the raster image.
>
> Although the areas are contiguos, their natural shape is very contorted
(one
> layer has 26 'islands') and sometimes only one pixel wide (one layer is a
> road). Could thin diagonals and/or and the contorted shape of some
landuse
> areas be causing this problem? How can I fix it? The vector image takes
a
> very long time to load in CartaLinx (a program that I am unfamiliar with)
> and when it does load boundaries appear correctly formed.
>
> Thanks in advance for any suggestions.
>
> Les McNamara
> University of Western Sydney
>
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