Straight Line Allocation and Direction functions

The Straight Line Allocation function creates a surface where each cell is assigned to the nearest source based on the straight line distance between them. If there is only one source, then all of the cells in the surface are allocated to that one source.

If there is more than one source, the surface is partitioned into areas of adjacent cells. You can think of the partitioned areas as compartments dedicated to one feature, such as the location of a hospital or a store. The size and shape of the compartments is determined by the proximity of the cells to the sources.

If there is more than one source in a straight line allocation surface, then cells are assigned to the nearest source. Even if the distance between a cell and more than one source is the same, the cell is assigned to only one source.

The cell values in a straight line direction surface point the way back to the nearest source, indicating the direction, in degrees azimuth, back to the source. Imagine a compass, like the one below, hovering over each cell in the surface.

In a straight line direction surface, the cell values are based on degrees azimuth. With a value of 360, north is the top of the surface.

If there is more than one source, the cell value is the direction to the nearest source.

In this graphic, source 1 is the nearest source to cell A and, judging by the angle, is located in a straight line direction of about 15 degrees from cell A. Source 2 lies in a direction of 135 degrees from cell B. Source 3, 320 degrees from cell C. The source cells, in gray, have a value of zero, or no direction.