Generate Line Distance Raster

Feature Description

The Generate Line Distance Raster function produces corresponding line distance raster, straight direction raster, and straight allocation raster based on the source dataset.

Line Distance Raster: Represents the distance from each cell to the nearest source, where the raster value equals the Euclidean distance between the current cell and the nearest source. The nearest source is the one with the minimum straight-line distance from the current cell to all sources. For each cell, the distance to a source is calculated by connecting their centers and using the Pythagorean theorem with the two orthogonal sides of the right triangle formed. Thus, Euclidean distance calculation depends only on cell size (resolution). The diagram below illustrates straight-line measurement, with source raster cell size set to 10.

The distance L from the cell at row 3, column 3 to the source is:

Straight Direction Raster: Indicates the azimuth direction from each cell to its nearest source. Raster values represent the clockwise angle in degrees from due east (90°), with due south as 180°, due west as 270°, and due north as 360°. Cells corresponding to sources have a value of 0°, with valid range 0-360°.

Straight Allocation Raster: Identifies the nearest source for each cell. Raster values correspond to the source's grid value (for raster sources) or SMID (for vector sources). The diagram below demonstrates line distance raster generation with cell size 2.

For example, using vector point data representing hospital locations, executing Euclidean distance generation produces three datasets:

  • Line Distance Raster: Each cell's distance to the nearest hospital.
  • Straight Direction Raster: Azimuth direction from each cell to the nearest hospital.
  • Straight Allocation Raster: Divides the area into regions allocated to each of the eight hospital points.

In practical applications, line distance raster is suitable for scenarios without obstacles or uniform travel costs. For instance, rescue aircraft can use it to determine distances to hospitals with no aerial obstacles. The allocation raster identifies the nearest hospital, while the direction raster provides orientation. However, for ground vehicles encountering varied terrain costs, Euclidean distance becomes inadequate.

Feature Entry

  • "Spatial Analysis" Tab->"Raster Analysis" Group->"Distance Raster" Drop-down Button->"Generate Distance Raster (Euclidean)".
  • Toolbox->Distance Raster->Generate Distance Raster (Euclidean).

Steps

  • Source Data Settings: Configure data source and dataset containing source features. Sources can be vector or raster data representing features of interest (e.g., wells, roads, schools).
  • Parameters: Set distance grid parameters including max distance and resolution.

    Max Distance: Defines the maximum output distance. Cells beyond this distance receive NoData. Default 0 indicates no distance limit. Optional parameter.

    Resolution: Specifies output dataset resolution. Default uses 1/500th of the diagonal length of source dataset bounds. Optional parameter.

  • Set Result Data: Select output datasource and specify names for distance raster, direction raster, and allocation raster. Default names: result_StraightDistance, result_StraightDirection, result_StraightAllocation.
  • Click "Environment Settings" to configure analysis environment parameters, including geographic extent, clip bounds, and default cell size. Refer to Setting Analysis Environment for details.

    Note: Environment parameters can be set as global defaults for raster analysis. Unset parameters will use values from raster analysis environment settings.

  • Click "OK" to execute. Click "Cancel" to exit.

Application Example

Using river raster data from a region with max distance 0 and resolution 25 (matching source data), three output datasets are generated:

  • Line Distance Raster: Each cell's minimum distance to river features (valued areas).
  • Straight Direction Raster: Azimuth direction to nearest river cell.
  • Straight Allocation Raster: Allocation of cells to nearest river segments.

Related Topics

Distance Raster Overview

Generate Surface Distance Raster

Generate Custom Cost Distance Raster