Scale-triggered display problem with mosaicked elevation raster

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06-21-2014 07:55 AM
NeilCurri
New Contributor II
Hello,

I have 2 adjoining DEM rasters that I have combined into a single, continuous raster using Mosaic To New Raster. The two source rasters overlap, and both have some 0 pixel values around their edges. Here's the overlap of one atop the other:

[ATTACH=CONFIG]34792[/ATTACH]

Here are the options I am using in the Mosaic to New Raster tool:

[ATTACH=CONFIG]34794[/ATTACH]

In order to deal with the overlap and the fact that some of the pixels at the edge = 0, I set the Mosaic Operator to Maximum. Raster values are in Meters and range from 0 to 1,683, so I use 32 bit unsigned as the Pixel Type. The mosaicked raster looks fine at the boundary. However, at the southeast edge, there is some odd banding that is happening in the display. This is how it looks at 1:125,000 scale, with 2 odd bands of pixels at seemingly odd ranges from the neighboring pixels:

[ATTACH=CONFIG]34795[/ATTACH]

One of the odd band of pixels goes away when zoomed in at higher scales, but one remains. Here it is at 1:60,000:

[ATTACH=CONFIG]34796[/ATTACH]

At scales higher than 1:1:57,311, both odd bands of pixels disappear and the raster looks "normal". Here it is at 1:50,000:

[ATTACH=CONFIG]34797[/ATTACH]

Why the odd display, and why only at smaller scales? Looking at these again, it appears as if the odd bands of pixels are "ghosts" of other parts of the raster.
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by Anonymous User
Not applicable
Original User: ncurri

The problem seems to be with using "maximum" as the Mosaic Operator in the Mosaic to New Raster tool.

When I use "maximum" I can repeat the display problem I described in my first post. However, if I first use SETNULL function to set all 0 values in my overlapping source rasters to null - that way I can use "first" or "last" as the Mosaic Operator instead of "maximum" - the resulting mosaicked raster displays fine at all scales.

Weird.
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