petronilamandeno

contour lines in grids

Discussion created by petronilamandeno on Nov 30, 2011
Latest reply on Apr 3, 2012 by petronilamandeno
I wasn't too sure how to describe this problem, and there may be two different problems, so I just titled this with the terms above as that is the results that I get: in a hillshade of an elevation grid, it appears as if the contour lines are etched into it.

The original files are tiled ASCII grids delivered by a LiDAR contractor.  The ASCII files are presumably created from the original LAS point cloud dataset.  It appears that way when I look at the ASCII file in GlobalMapper (a GIS program) and zoom in and can see all the trails and cool divets and hills.  Here's how the file looks in GlobalMapper:

I very nice surface.

Here's how it looks when I add it to ArcMap:

Not a very nice image.

As you can see, the data range is weird, from -2147483648 to 2147483647.  However, if I export it from ArcMap to another data format (say, ESRI GRID format), I get this:


The data range is right now, but it's got this funky contour line thing going on, and if I apply an on-the-fly (or permanent) hillshade effect, it looks like this:


For the level of detail I can get in GlobalMapping on the original dataset, this is, of course, completely unacceptable.

I have 50 more of these tiles, all at .5m resolution.  I need to merge this all into one surface and I can't very well do that at the moment and have it looking like someone drew it.  I know I'm doing something stupid or overlooking some setting, but I've been working in ArcMap for years and this is the first I've come across this and I really don't know what I'm missing.  Any clue?

Thanks in advance and my apologies for the size of the images.  There doesn't appear to be a way to re-size them via the forum. :(

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