Dear all,
I am trying to select the cells of an asc grid that intersect a polyline shape. My algorithm works fine but I found a "strange" behaviour concerning the asc grid visualization in map window.
In particular the first column has the width=37.5,
the last row (up) has the same width.
The last column and the the first row (bottom) have width=12.5.

The dtm I used is the following:

NCOLS 5
NROWS 5
XLLCENTER 12.5
YLLCENTER 12.5
DX 25
DY 25
NODATA_VALUE 0
1 2 1 4 1
2 3 2 5 2
3 4 3 1 3
4 5 4 2 4
5 1 5 3 5

The polyline is the following:
(12.5,12.5),(112.5, 112.5), (12.5,112.5)

The cells I've selected are the right ones as reported in the following grid.
NCOLS 5
NROWS 5
XLLCENTER 12.500000
YLLCENTER 12.500000
DX 25
DY 25
NODATA_VALUE 0
9 9 9 9 9
0 0 0 9 0
0 0 9 0 0
0 9 0 0 0
9 0 0 0 0

In attach you can find the files I'm using.
Best wishes,
Tonino

Hello, is there anyone who has observed this kind of problem when an asc grid is visualized in the mapwindow's main view? (The upper row and the first left column have a width 1.5 times the cell width? The first column on the right and the bottom row have a similar problem but the width is just the half of the cell width).
Tonino

Hi,

I have found a problem in the visualization of the ESRI ASCII GRID file format.
The image boundary is correct but all the cells in the first row and in first column are bigger (1.5 times), all the other cell are of the right size but are shifted of half cell size (both in x and y direction) and all the cell in the last row and in the last column are littler (0.5 times).

Anyone can easily reproduce the problem loading the following example file in MapWindow Gis 4.8.6 (as attach an image showing the problem):
_________________________________________________________________________________
ncols 2
nrows 2
xllcorner 0
yllcorner 0
cellsize 1
NODATA_value -9999
1 2
3 4
_________________________________________________________________________________
Only 4 cells and each cell has a different size.
The solution of this problem is fundamental for me otherwise I will be forced to leave MapWindow for another GIS tool.

Thanks
Gianni

sorry,Gianni
I have no skill to help you.
just wanted to ask what the PROGEA tool in your attachement is.

sandro