Edit elevation pixels

Disponible avec une licence Image Analyst.

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

The Capture group contains the Copy Region and Replace Region tools. These tools copy or replace pixels from the same dataset or from a different dataset in the map. If using another dataset within the map, use the Source Layer drop-down list to set the correct map layer to use; this layer must have the same bit depth as the raster being edited. The target layer is always the raster dataset that you are editing.

The Inspect group contains tools that work with elevation data. Locate Outliers highlights 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 the Outlier Filter tool to remove these anomalies from the elevation data. Find Minimum and Maximum highlights 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 deselect the pixels from either Locate Outliers or Find Minimum and Maximum, click the Clear Pixel Selection button in the Inspect group. 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).

The Edit tab allows you to interactively replace pixel values:

• Replace Value At replaces each pixel specified
• Replace Value Within replaces values in the specified region.

Type a value in the New Value 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 the selected region, of the elevation data. See the table below for the available tools.

Icon	Operation or filter	Description
	Add To	Add to, or subtract from, a specified value for all the pixels in the selected region. Positive values add to the pixel value, and negative values subtract from the pixel value.
	Blur	Obscure 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.
	Custom Processing	Apply a raster processing template (.rft.xml) to the selected region. The following two factors must be true for the operation to be successful: Both the input (raster being edited) and the output region must have the exact same properties, such as number of bands, bit-depth, and so on. The parameters in the processing template must all be valid.
	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. 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 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 void 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 must 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 remains a void. The units of this parameter are the same as the units used in your data's spatial reference system.
	Interpolate from Edges	Use values from the edges of your selected region to interpolate the surface. This can be used to remove nonground features or fill NoData gaps. There are four Interpolation Methods for this function: Nearest Neighbor—Calculate pixel value using the nearest pixel. Linear Tinning—Use a triangulated irregular network from the center points of each pixel in the irregular raster to interpolate a surface that is then converted to a raster having a regular pixel grid. Natural Neighbor—Find the closest subset of input samples to a query point and weights them appropriately to compute an interpolated value. See How Natural Neighbor works for more information on this method. Inverse Distance Weighting—Determine pixel values using a linearly weighted combination of a set of sample points or pixels. The weight is a function of the inverse of the distance from the known points or pixels. If you select the Blend check box, the result of the operation buffers the region and interpolates the buffered area, so that the result looks seamless. The Blend Width text box allows you to specify the number of pixels to use in the blending interpolation. The blending uses the same interpolation method that was specified for the operation.
	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 NoData gaps. There are four Interpolation Methods for this function: Nearest Neighbor—Calculate pixel value using the nearest pixel. Linear Tinning—Use a triangulated irregular network from the center points of each pixel in the irregular raster to interpolate a surface that is then converted to a raster having a regular pixel grid. Natural Neighbor—Find the closest subset of input samples to a query point and weights them appropriately to compute an interpolated value. See How Natural Neighbor works for more information on this method. Inverse Distance Weighting—Determine pixel values using a linearly weighted combination of a set of sample points or pixels. The weight is a function of the inverse of the distance from the known points or pixels. If you select the Blend check box, the result of the operation buffers the region and interpolates the buffered area, so that the result looks seamless. The Blend Width text box allows you to specify the number of pixels to use in the blending interpolation. The blending uses the same interpolation method that was specified for the operation.
	Pixelate	Obscure 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 create more pixelation. Check the Sharpen check box to sharpen the image that has been obscured. This will make the region less noticeably obscured.
	Set Average	Set the selected region to its computed average elevation.
	Set Constant	Set the selected region to a constant elevation. Specify the Value to apply to the region.
	Set NoData	Set the pixels in the selected region as NoData pixels for each band.
	Average Filter	Use an average filter on the selected region. This smooths 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.
	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.
	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.
	Outlier Filter	Remove outlier pixels and other noise within the region. For example, if there was a flock of birds in the sky when the lidar data was captured, this removes 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.
	Terrain Filter	Remove aboveground 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 are typically missed by the Conservative option but does not capture the type of sharp reliefs that are captured by the Aggressive option. This 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, that 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 taller objects—such as utility towers, vegetation, and portions of buildings—as ground.

Remarque :

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

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