Weight map for distance calculation

A weight map is optional input for a distance calculation. If all parts in your map are equally accessible, there is no need to specify a weight map: the system assumes a weight of 1 for all undefined pixels.

• To exclude inaccessible areas from a distance calculation or to indicate insurpassable barriers, prepare a weight map in which negative values or the undefined value are assigned to inaccessible areas; assign value 1 to accessible pixels.
• To work with relative accessibility, prepare a weight map in which weight values represent the relative difficulty to surpass pixels.
• To calculate a travel time map, prepare a weight map in which weight values are inversely proportional to the relative speed that can be obtained in the different mapping units.

In a weight map, value 1 means normal accessibility, positive values represent a factor of resistance, and negative values represent insurpassable barriers i.e. inaccessible areas. Value 0 in a weight map means free accessibility, distance/time values will not increase while passing these areas.