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Editing elevation pixels

Available with Image Analyst license.

Pixel Editor can be used to edit elevation rasters, such as digital elevation models (DEM), digital surface models (DSM), or digital terrain models (DTM). The Capture group allows you to replace a region of pixels within another region. There are tools to view your elevation data on the Inspect group of the Pixel Editor tab, and there are tools and Operations that can be applied to the data on the Edit tab.

The Capture group has two tools: Copy Copy Region and Replace Replace Region. Copy allows you to specify an area in the region in which you want to copy the pixels, and then dynamically move and apply it to a different area. Replace allows you to specify a region that you want replaced, and lets you dynamically drag the working region to another area to be used to fill it. Both of these tools work on pixels from the current layer being edited, or you can choose another raster layer to work with in the map by specifying the Source Layer.

The Inspect group has tools that work with elevation data. Locate Outliers Locate Outliers will highlight the pixels that statistically deviate from normal values, within the selected region of interest. Pixel values that are three or more standard deviations away from the normal range of values are considered outliers. Once these outliers have been identified, you can use operations such as the Outlier Filter Outlier Filter to remove these anomalies from the elevation data. Find Minimum and Maximum Find Minimum and Maximum will highlight the minimum and maximum values within the selected region of interest. Minimum pixels are displayed in green and maximum pixels are displayed in red. To unselect the pixels from either Locate Outliers or Find Minimum and Maximum, click the Clear Pixel Selection Clear Search button on the Inspect group. Shaded Relief Shaded Relief allows you to visualize your elevation data in its native form, or as shaded relief. The shaded relief view can help you identify abrupt changes or subtleties in elevation that may be difficult to visualize on a digital elevation model (DEM).

DEM view
Shaded relief view of a DEM

The Edit tab allows you to interactively Replace Value At Replace Value At each pixel specified, or Replace Value Within Replace Value Within the specified region. Type the New Value in the text box. Then use the Replace Value At or Replace Value Within tool to specify the location to replace the values. If your text box is left blank, the new value will be NoData.

There are several operations that can be applied to elevation data. See the table below for the available tools.

IconOperation or filterDescription
Add to

Add To

Add to, or subtract from, a specified value for all the pixels in the selected region.

Positive values will add to the pixel value, and negative values will subtract from the pixel value.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Blur

Blur

Obscures the selected region with a blurred effect. Blur can also be used to smooth a noisy area.

The Factor option allows you to set the level of blurring to perform, in which higher values result in more blurring.

Check the Sharpen check box to sharpen the image that has been obscured. This will make the region less noticeably obscured.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Elevation Void Fill

Fill Voids

Create pixels where NoData voids exist in your elevation dataset. Voids are often caused by water bodies, insufficient stereo overlap, class type selection, or exclusion. Void filling is most commonly performed when generating a ground surface.

The Fill Method allows you to choose the maximum width of a void to fill.

  • Fill All—All the voids will be filled, regardless of the void's width. This method is the default.
  • None—None of the voids will be filled. Small voids can still be filled using the Short Range IDW parameter.
  • Maximum Void Size—The maximum void width value is used to specify the largest size of a void that you want to fill. If the width or height of the bounding box around the void is larger than the maximum void width value, the void is not filled. The units of this parameter are the same as the units used in your data's spatial reference system.

Check the Short Range IDW check box to fill small voids using the inverse distance weight (IDW) algorithm. If you turn on this parameter, you need to specify the maximum Search Radius that will be used for void filling. A void that is farther away, from any valid pixel, than this threshold value will remain as a void. The units of this parameter are the same as the units used in your data's spatial reference system.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Interpolate From Vertices

Interpolate from Vertices

Use values from the vertices of your selected region to interpolate the surface.

This can be used to remove nonground features or fill in NoData gaps.

There are four resampling methods for this function:

  • Nearest Neighbor—Calculates pixel value using the nearest pixel. If no source pixel exists, then no new pixel can be created in the output.
  • Linear tinning—Uses a triangular irregular network from the center points of each cell in the irregular raster to interpolate a surface which is then converted to a regular raster.
  • Natural Neighbor—Finds the closest subset of input samples to a query point and applies weights to them based on proportionate areas to interpolate a value.
  • Inverse Distance Weighting—Determines cell values using a linearly weighted combination of a set of sample points or cells. The weight is a function of the inverse of the distance from the known points or cells.

If you use the Blend check box, the result of the operation will buffer the region and interpolate the buffered area, so that the result looks seamless. The Blend Width text box allows you to specify how many pixels should be used in the blending interpolation. The blending will use the same interpolation method that was specified for the operation.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Pixelate

Pixelate

Obscures the region by resampling the region to an exaggerated pixel size.

The Factor option allows you to set the level of resampling to perform, in which higher values will create more pixelation.

Check the Sharpen check box to sharpen the image that has been obscured. This will make the region less noticeably obscured.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Set Average

Set Average

Set the selected region to its computed average elevation.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Set Constant

Set Constant

Set the selected region to a constant elevation.

Specify the Value to apply to the region.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Set NoData

Set NoData

Set the pixels in the selected region as NoData pixels, for each band.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Average Filter

Average Filter

Use an average filter on the selected region. This will smooth the elevation values within the region.

The Filter Size option allows you to choose the size of your filter window while performing the operation. A filter size of 8 means you are using an 8 by 8 filter window. Larger values result in more smoothing.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Constrained Filter

Constrained Filter

Use an average filter that has a threshold on the maximum a value can change, within the selected region.

The Filter Size option allows you to choose the size of your filter window while performing the operation. A filter size of 8 means you are using an 8 by 8 filter window. Larger values result in more smoothing.

The Threshold is the maximum value that the pixel can change. If the change is larger than the threshold, the original pixel value remains unchanged.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Median Filter

Median Filter

Use a median filter on the selected region.

The Filter Size option allows you to choose the size of your filter window while performing the operation. A filter size of 8 means you are using an 8 by 8 filter window. Larger values result in more smoothing.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Outlier Filter

Outlier Filter

A filter that removes outlier pixels and other noise within the region.

For example, there may have been a flock of birds in the sky when the lidar data was captured. This can remove such anomalies from your source elevation.

The Filter Size option allows you to choose the size of your filter window while performing the operation. A filter size of 8 means you are using an 8 by 8 filter window. Larger values result in more smoothing.

The Threshold is the number of standard deviations separating a pixel value before it is considered an outlier.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

Terrain Filter

Terrain Filter

Removes above ground structures in a DSM, while preserving natural slopes in the selected region.

Three method are used for detecting ground points.

  • Standard—This method has a tolerance for slope variation that allows it to capture gradual undulations in the ground's topography that would typically be missed by the conservative option, but not capture the type of sharp reliefs that would be captured by the aggressive option. This method is the default.
  • Conservative—When compared to other options, this method employs a tighter restriction on the variation of the ground's slope, allowing it to differentiate the ground from low-lying vegetation such as grass and shrubbery. It is best suited for flat topography.
  • Aggressive—This method detects ground areas with sharper reliefs, such as ridges and hilltops, which may be ignored by the standard method. Avoid using this method in urban areas or flat, rural areas, as it may result in the misclassification of higher objects—such as utility towers, vegetation, and portions of buildings—as ground.

When the Exclude Region Intersections check box is checked, any regions that intersect the active region will be excluded from this operation.

The Undo button Undo can be used to reverse the last action that was performed with the tools on the Pixel Editor tab. Undo can also be performed by pressing Ctrl+Z; this shortcut can also be used to undo actions that were performed within the Pixel Editor Operations pane. The Redo button Redo can be used to reverse the undo action that was performed with the tools on the Pixel Editor tab. Redo can also be performed by pressing Ctrl+Y; this shortcut can also be used to redo actions that were performed within the Pixel Editor Operations pane.

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