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The Heat Map tool considers individual records (e.g. customers) as sources of "heat" (e.g. demand) and generates polygons representing different levels of heat in a given area. This can be helpful by rendering a large amount of point-level detail as more intuitively understandable hot spots.
The tool divides the world into grid cells and calculates a heat level for each cell by giving the cell full credit for heat sources within it, and some smaller amount of heat from nearby cells. Cells are then tiled relative to one another and aggregated into polygons.
There are two tabs that require user input to successfully configure the tool:
Input - Two input fields are considered:
A spatial object field containing points the represent the heat sources.
An optional numeric field specifying how "hot" this particular point is. If the points represent customers, this might be a revenue figure, for example. If this is omitted, all points will be considered to generate equal heat.
Questions - The tool is configured with 5 parameters:
Grid Size: The tool's process is based on grid cells. A smaller grid size will produce more grid cells, giving a more detailed map as a result, but will take longer to process. Since the processing time is related to the grid size exponentially, even a small increase in size can impact the run time considerably.
Max Distance: This is the maximum distance at which heat from one cell can contribute to the final heat level of another cell. While heat propagation generally decreases with distance, it is helpful to entirely cut it off at some point to avoid excessive processing time calculating insignificant contributions from far away cells.
Decay Function: Cells get full heat from points inside them, and no heat from points beyond the max distance, but in between they must get some fraction based on the distance to the heat source. This is controlled by the decay function. The default (1 - [Distance]/[MaxDistance]), gives a simple linear slope.
Smooth Results: The results of the tool consist of aggregated grid cells, which can look quite jagged. Selecting this will cause a series of smooth/generalize operations designed to straighten edges and round corners.
Output Type: The tool produces polygons representing different levels of heat. It can be helpful to have these as either non-overlapping "Donuts" each containing a single heat level, or as "Stacked" polygons each containing their own heat level, and all higher levels.
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