Generate Surface Distance Raster.

Instructions for use

The Generate Surface Distance Raster function generates the appropriate Surface Distance Raster, surface orientation grid, and surface distribution grid based on the Source Dataset and surface grid.

Surface Distance Raster: Used to express the shortest surface distance of each cell on the surface grid to the nearest source. The closest source is the one from which the current cell reaches the Min Distance of all sources. For a grid with no value in the surface grid, the distance result is still calculated as no value. The Calculator Method for the surface distance d from the current cell (set as G1) to the next cell (set as G2) is:

Where, B is the difference between the grid value (i.e., elevation) of G1 and the grid value of G2; A is the Straight-line Distance between the center points of G1 and G2, and the value of a is equal to the cell size when G2 is one of the upper, lower, left, and right cells adjacent to G1; When G2 is one of the four cells diagonally adjacent to G1, the value of a is the cell size multiplied by the square root of 2.

Surface Direction Grid: Used to express the direction of travel of the shortest surface distance path for each cell on the surface grid to reach the nearest source. In the surface direction grid, there are eight possible directions of travel (True North, True South, True West, True East, Northwest, Southwest, Southeast, Northeast), which are encoded using integers from 1 to 8, as shown in the following figure. Note that the cell where the source is located has a value of 0 in the surface orientation grid, and the cell with no value in the surface grid is assigned a value of 15 in the output surface orientation grid.

Surface Distribution Grid: It is used to mark the nearest source of each cell on the surface grid, and its grid value is the value of the nearest source of the current cell (when the source is a grid, it is the grid value of the nearest source; when the source is a vector object, it is the SMID of the nearest source). Cells with no value in the surface grid remain with no value in the exported surface assignment grid.

For example, the Source Dataset is a Point Dataset, where the point represents the location of the hospital within the range, and the surface grid is the DEM grid of the corresponding area. Execute the generated surface distance on this data to obtain three datasets, as shown in the following figure:

  • Surface Distance Raster: the distance from each pixel in Result Dataset to the nearest Source Dataset (point), namely, the distance from each pixel to the nearest hospital.
  • Surface direction grid: the direction of each pixel in the Result Dataset to the nearest Source Dataset (point), that is, the direction of each pixel to the nearest hospital.
  • Surface allocation grid: according to the distribution of hospitals, other pixels are allocated to the point data in the source data. If there are eight point data at present, eight areas are divided.

Function entrance

  • Spatial Analysis tab-> Raster Analysis group-> Distance Raster Drop-down Button-> " Generate Distance Raster".
  • Toolbox-> Raster Analysis-> Distance Raster-> Generate Distance Raster.

Operation steps

  1. Source Data Settings: Set the Datasource of the source data and select the Dataset where the source data is stored. The source data is the ground features or objects we are interested in, such as wells, roads or schools, which can be Vector Data or Raster Data.
  2. Surface Raster Data setting: Set the Datasource of the Surface Raster Data, and select the DEM Raster Dataset in the Datasource.

    The Cost Data set gives the cost of each pixel, which can be height, slope, etc. For example, the journey over a mountain to reach the destination may be shorter, but the time around it may be longer.

  3. Parameter Settings: Set the Distance Raster parameter, including Max Distance and resolution.
    • Maximum uphill angle: The uphill angle is the angle between the uphill direction and the horizontal plane. When the actual uphill angle is greater than maximum uphill angle, this direction of travel is not considered. The default maximum uphill angle is 90 °, that is, it is not limited by the uphill angle.
    • Maximum Downhill Angle: Downhill angle is the angle between the downhill angle and the horizontal plane. Similarly, when the actual downhill angle is greater than maximum downhill angle, this direction of travel is not taken into account. The default maximum downhill angle is 90 °, that is, the current analysis is not limited by the downhill angle.

      • Note: If the maximum uphill (downhill) angle is set, the Analyst Result may not be obtained, and there may be no path meeting the condition in the input Terrain Data.

    • Max Distance: used to set the Max Distance of the generated Distance Raster. The default value is 0, indicating that the result is not limited by the distance. This parameter is optional. When Max Distance is set (a value other than 0), the cell's value is set to no value in the Distance Raster, the Assignment grid, and the Orientation grid when the cell's minimum surface distance to the nearest source is greater than Max Distance.
    • Resolution: Set the resolution of Result Dataset. The default value uses 1/500th of the diagonal length of the rectangle corresponding to the source Dataset Bounds. This parameter is optional.
  4. Set Result Data. Select Result Data Datasource to save, Surface Distance Raster Data, Surface Orientation Raster Data, and Surface Assignment Raster Data result name. The default generated Distance Dataset Name is result _ Surface Distance, and the Direction Dataset is result _ Surface Direction. Allocation Dataset is a result _ SurfaceAllocation.
  5. Click the Environment Settings button to set the Analysis Environment parameters. The Analysis Environment parameters supported by the Generate Distance Raster include the Geographic Range, Clip Bounds, and Default Cell Size of the Result Dataset. Please refer to the Set up the Analysis Environment page for specific operations.

    Note: The environment parameter Set As Global is supported, that is, the parameter value set here is used as the total Raster Environment Analyst environment parameter. Other functions that support the environment Parameter Settings are not required to be set repeatedly. If an environment parameter is not set here, the setting of the parameter in the Raster Analysis Environment is read during analysis.

  6. Click the Execute button to execute the action that generates the Surface Distance Raster.

Application example

Calculate the surface distance, surface direction and surface distribution of the area by using the existing Raster Data and DEM Data of the river in a certain area as the Source Dataset and the DEM Data as the Surface Raster Data. With the maximum uphill and downhill angles set to 90 degrees, the Max Distance set to 0, and the resolution set to 25, the default resolution of the current source Raster Data, the result is three Datasets containing the Surface Distance Raster, the surface orientation grid, and the surface distribution grid:

  • Surface Distance Raster: refers to the distance from each pixel in the grid range to the nearest surface of the river (value area) in the source data.
  • Surface direction grid: refers to the surface direction of the nearest pixel from each pixel in the grid range to the river (value area) in the source data.
  • Surface assignment grid: In the result Raster Data, the grid value of each cell is the value of the nearest source of the current cell (other pixels are assigned to the source grid river (valued area) data according to the distribution of rivers).

Related topics

Distance Raster overview

Generate Line Distance Raster.

Build Custom Cost Distance Raster