DEM editing operations

Each operation is described in the following table.

Operation	Description
Average filter	Applies a smoothing filter to the pixels under the mask. This filter is useful for flattening areas while still preserving the overall terrain. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width of the blend. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Median filter	Applies a median smoothing filter to the pixels under the mask. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. Large values, such as `100`, can flatten roads side-to-side and completely filter out small bumps, such as a car. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Noise filter	Computes the sigma and mean for the polygon. If the working area is greater than the sum of the mean and the product of the threshold multiplied by the sigma, it will be replaced with the average of the surrounding information. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. The value you enter in the Threshold box determines the range of values replaced. That is, if the working area is greater than the sum of the mean and the product of the threshold multiplied by the sigma, it will be replaced with the average of the surrounding information. The default Threshold value is `1.5`. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Hybrid median filter	A filter well suited to preserving building corners. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Rotated hybrid median filter	A slightly modified version of Hybrid median filter that preserves building corners, but may be better at removing hatching patterns that occur in areas of the digital surface model (DSM) produced by using the Semi-Global Matching (SGM) method. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Clamp filter	Applies a limited-average filter to the pixels under the mask. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. The value you enter in the Clamp box defines the maximum amount, in meters, by which to change a pixel. This ensures that abrupt elevation changes, such as, cliffs or buildings, are not filtered out while smoothing out small anomalies. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Terrain filter (flat)	Optimized for flat terrain, this filter removes elevation values that correspond to buildings and canopies, and replaces the pixels under the mask with an estimation of the bare Earth. The value you enter in the Size box defines the size of the filter. The default value is `100` for a filter size of 100 x 100 pixels, or the value specified previously. The value you enter in the Gradient box defines the maximum slope, in degrees, that corresponds to a natural feature, such as a hill. The default value is `30`, or the value specified previously. With this option, the operation attempts to preserve features with slopes below the specified threshold. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Terrain filter (hilly)	Optimized for hilly terrain, this filter removes elevation values that correspond to buildings and canopies, and replaces the pixels under the mask with an estimation of the bare Earth. The value you enter in the Size box defines the size of the filter. The default value is `100` for a filter size of 100 x 100 pixels, or the value specified previously. The value you enter in the Gradient box defines the maximum slope, in degrees, that corresponds to a natural feature, such as a hill. The default value is `30`, or the value specified previously. With this option, the operation attempts to preserve features with slopes below the specified threshold. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Remove bumps (flat)	Similar to Terrain filter (flat), but with different options, this filter attempts to remove bumps from the landscape in the area under the mask. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. The value you enter in the Gradient box defines the maximum slope, in degrees, a bump must have for it to be removed. Lower values will remove more bumps, but will also remove terrain features that were intended to be kept. The default value is `5`, or the value specified previously. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Remove bumps (hilly)	Similar to Terrain filter (hilly), but with different options, this filter attempts to remove bumps from the landscape in the area under the mask. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. The value you enter in the Gradient box defines the maximum slope, in degrees, a bump must have for it to be removed. Lower values will remove more bumps, but will also remove terrain features that were intended to be kept. The default value is `5`, or the value specified previously. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Remove bumps (keep linear)	Similar to Remove bumps (hilly), but with different options, this filter attempts to preserve long, thin shapes that Remove bumps (hilly) might otherwise remove. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. The value you enter in the Gradient box defines the maximum slope, in degrees, a bump must have for it to be removed. Lower values will remove more bumps, but will also remove terrain features that were intended to be kept. The default value is `5`, or the value specified previously. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Remove pits (flat)	Optimized for flat terrain, this filter attempts to fill in pits from the landscape in the area under the mask. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. The value you enter in the Gradient box defines the maximum slope, in degrees, a bump must have for it to be removed. Lower values will remove more bumps, but will also add terrain features that were not there originally. The default value is `5`, or the value specified previously. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Remove pits (hilly)	Optimized for hilly terrain, this filter attempts to fill in pits from the landscape in the area under the mask. The value you enter in the Size box defines the size of the filter. The default value is `7` for a filter size of 7 x 7 pixels, or the value specified previously. The value you enter in the Gradient box defines the maximum slope, in degrees, a bump must have for it to be removed. Lower values will remove more bumps, but will also add terrain features that were not there originally. The default value is `5`, or the value specified previously. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Fill from edges	Removes the data under the polygon and fills it by using values from the edges of the polygon. This method is useful for stripping features to get to bare-Earth elevations when you are confident that the polygon edges have accurate elevation values. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width of the blend. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Fill from vertices	Removes the data under the polygon and fills it by using values from the digital elevation model (DEM) at the location of the polygon vertices. This method is useful for stripping features to get to bare-Earth elevations when you draw a polygon so the vertices are at accurate elevation locations. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width of the blend. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Fill from polygon	When opening a vector layer from another source that has an elevation value associated with the vertex of the polygon, this filter will fill in using that elevation. This filter is useful for setting the height of lakes. If the polygon is one you created, this operation acts exactly like Fill from vertices: it removes the data under the polygon and fills it using values from the DEM at the location of the polygon vertices. This is useful for stripping features to get to bare-Earth elevations when you draw a polygon, so the vertices are at accurate locations of elevation. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width of the blend. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Opposite ends fill (blend all sides)	Useful for editing features, such as bridges. The filter examines the selected polygon on each short end and finds an average elevation for each; for example, where a bridge touches the ground. The two elevations are then used in an interpolation along the length of the bridge. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width of the blend. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Opposite ends fill (blend ends only)	Useful for editing features, such as bridges. The filter examines the selected polygon on each short end and finds an average elevation for each; for example, where a bridge touches the ground. The two elevations are then used in an interpolation along the length of the bridge. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width of the blend. With this method, the blend applies only to each short end of the polygon. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Road average filter	Applies an average filter under the mask, but differently than Average filter. This filter is useful for flattening roads while preserving the inclines in the road. The filter does not read outside the mask, except from the ends. This ensures that features not on the road do not creep into the roads, except at the ends, where the road should blend into the road outside the mask. The value you enter in the Size box defines the size of the filter. The default value is `15` for a filter size of 15 x 15 pixels, or the value specified previously. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Road median filter	Similar to Road average filter, except it uses a Median filter instead of an Average filter. The value you enter in the Size box defines the size of the filter. The default value is `15` for a filter size of 15 x 15 pixels, or the value specified previously. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Average elevation	All DEM pixels under the polygon are set to the average of all of the pixels. After you click Apply, the Elev box displays the average value computed. This filter is useful for setting areas, such as lakes, to be flat. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Constant elevation	Sets the elevation value you enter in the Elev box to all pixels under the polygon. This filter is useful for setting a lake to a predetermined height, or for creating a "clean" building shape. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width of the blend. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Add to elevation	Adds the value you enter in the Elev box to all pixels under the polygon. This filter is useful for removing forests of a specific height while still following the general contour of the terrain. To decrease DEM values, enter a negative value in the Elev box. If necessary, you can also click the Blend check box, and then in the box to the right, enter a value for the width of the blend. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Average elevation blend up	Sets the elevation of all pixels under the polygon to the average elevation of all pixels under the polygon. This filter is similar to Average elevation, except, when blending, the pixel values are never set lower than the values at the edge of the polygon. The filter is useful for setting areas, such as lakes, to be flat. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.
Constant elevation blend up	Sets the elevation value you enter in the Elev box to all pixels under the polygon. This filter is similar to Constant elevation, except, when blending, the pixel values are never set lower than the values at the edge of the polygon. The filter is useful for setting areas, such as lakes, to be flat. If necessary, select the Apply blending subsequently check box to blend pixels under the active mask during future editing operations. If the active polygon represents an area that should not have a smooth transition between it and surrounding areas, such as a bridge, make sure the Apply blending subsequently check box is clear.