discrepancy between ASCII file and pixel size and pixel width in metadata.

yianni

Hi all,

I have an ASCII file that if I load it as an elevation grid from 3d point data and I choose to treat the 3rd coordinate value as elevation, it will load as expected as a nice colorful background

Now if I go to check the metadata of the file then the pixel width is 1.006 meters and the pixel height is 2.787 meters.

Also when I change the resampling of the specific file, from bilinear interpolation to say box average 2x2 the hole layer gets "pixelised" and if I physically measure the edges of the pixel, I get the same 1x2.7m, which is great ( I used to think that I just told GM to show me the ASCII as it actually is, no interpolations).

Here is where it gets confusing:

if I chose to load the same file as a point only from the "generic ascii text file input options" card (NOT as an elevation grid from 3d point data as I did before) I expect my screen to fill up with rows upon rows of points, which have as an attribute the elevation value of the specific location.

However, if I measure the spacing of those points it is different to the 1.0m x 2.7m as mentioned above. Actually in the file that I just tried to load, all points are now 0.5m. apart when I measure their distance on my screen with the GM distance ruler.

Any ideas on why is that? I was expecting to see a point every 1x2.7 m and not every 0.5m. Why do not I get a pixel size and width of 1m x 2.7m when the ASCII file has points are every 0.5m?

Any good ideas on the above? I am inclined to believe that I am doing something wrong or have gotten the idea backwards and some guidance would be nice..

On a different note I do remember seeing this weird 1.0m x 2.7m pixel width and height before in the metadata of XYZ files in global mapper. 

Thanks

y