| | 94 | * maximum_distance(Optional): Double Precision |
| | 95 | * Defines the threshold that the accumulative distance values cannot exceed. |
| | 96 | * Any cell location that has accumulative Euclidean distance value exceed this value will be assigned NoData for output value. |
| | 97 | * The default is to the edge of the output raster. |
| | 98 | * cell_size(Optional): Cell size of the output raster |
| | 99 | * Either set in the environment settings of the workspace |
| | 100 | * Or depends on if the input source is: |
| | 101 | * raster: same cell size as the input raster |
| | 102 | * feature: determined by the shorter of the width or height of the extent of input feature divided by 250. |
| | 103 | * out_direction_raster(Optional): Output raster dataset |
| | 104 | * The calculated direction (in degrees) each cell center is from the closest source cell center. |
| | 105 | * Return value: Raster Layer |
| | 106 | * The distance raster identifies the Euclidean distance for each cell to the closest source cell, set of source cells, or source location(s). |
| | 107 | * The distances are measured as Euclidean distance in the projection units of the raster, and are computed from cell center to cell center. |
| | 108 | * Algorithm |
| | 109 | * Euclidean distance is calculated from the center of the source cell to the center of each of the surrounding cells. The Euclidean algorithm works as follows: for each cell, the distance to each source cell is determined by calculating the hypotenuse with x and y distances between cell centers as the other two legs of the triangle.[[BR]] |
| | 110 | [[Image(http://help.arcgis.com/en/arcgisdesktop/10.0/help/009z/GUID-B6170E16-50FB-45FB-A724-E24251CDF305-web.gif)]] |
| | 111 | (Illustration from ArcGIS Online Help)[[BR]] |
| | 112 | * If the shortest distance to a source is less than the specified maximum distance, the value is assigned to the cell location on the output raster. |
| | 113 | * If the cell is at an equal distance to two or more sources, the cell is assigned to the source that is first encountered in the scanning process. User cannot control this scanning process. |
| | 114 | * The actual algorithm computes the information using a two-scan sequential process(need to figure it out?). This process makes the speed of the tool independent from the number of source cells, the distribution of the source cells, and the maximum distance specified. The only factor that influences the speed with which the tool executes is the size of the raster. The computation time is linearly proportional to the number of cells in the Analysis window. |
| | 115 | * Reference: |
| | 116 | [http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z0000001p000000.htm] |
