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Note: MacDEM's filters manipulate DEM elevation data. Image manipulations are already capabily handled by Photoshop, GraphicConverter, etc., so those functions are not included in MacDEM.

Though MacDEM generally merges DEMs seamlessly, sometimes there are gaps between DEMs. The Fill Gaps filter fills those gaps. Specifically, void elevations (those less than -32000) that are in gaps up to about 50 samples wide will be replaced with an interpolated value.

Displays a dialog box allowing you to find all occurrences of a given elevation value and replace them with another value. Note that if you click in the DEM before using this option, the "Change From" value will default to the elevation value of the sample you clicked on.

Changes the elevation units of the front window's DEM back and forth between meters and feet.

Scales the front window's DEM elevations by a user specified amount. The scale must be greater than or equal to 0.001. Scales less than one are allowed, but less than zero are not.

Scans the front window's DEM elevation data and replaces any values which are less than -32000 with zero.

Scales the front window's DEM elevation data for maximum dynamic range. The internal representation of the elevations are scaled by the largest value possible that keeps them within the range of a 16-bit integer. This gives the DEM the finest elevation resolution possible. The DEM's elevation resolution metadata is adjusted accordingly to maintain the same effective elevation values.

Using Normalize before a Mean 3x3 filter can sometimes provide for smoother results.

Another use would be to normalize the elevations prior to exporting to Photoshop. This will "brighten" the image in Photoshop, making it easier to see and work with. Photoshop's Levels would do this too, but could clip peaks if you are not careful.

Applies a 3x3 mean filter to smooth the elevation data in the front DEM window. Elevations of zero and elevations less than -32000 are not changed and are not used in computing means. This preserves coastlines and prevents void and fill data from affecting valid elevations.

Applies an adaptive filter to the elevation data to smooth out "stair steps" caused by elevation quantization. Sometimes very fine "contour lines" are visible in shaded reliefs due to elevation quantization (steps of 1 unit). Applying the Normalize filter to reduce the quantization, followed by the application of this filter, largely eliminates these lines. Elevations of zero and elevations less than -32000 are not changed and are not used in the filter. This preserves coastlines and prevents void and fill data from affecting valid elevations.