Slope algorithms and their effect on risk prediction

Slope and aspect were calculated by nine different methods.

Each method has been published, and can be considered to be a valid technique. The "Maxslope score" is the ratio of maximum value calculated for a particular algorithm, as a proportion of the maximum value calculated by the "Simple method".

Slope algorithms investigated

Method Maxslope score

Fleming and Hoffers (Ritter's) method 0.7523

Horn's 0.6746

One over distance 0.6674

Sharpnack and Akins 0.6607

Diagonal Ritter's 0.6411

Averaged down-dip slopes 0.7526

Simple method 1.0000

maximum downward gradient 0.8931

The slope map derived by each method was used as an input to the FIREMAP model. The resultant effect on the outputs of the model can be seen by selecting the results option at the top of this page, then choosing one of the methods from the menu.

A discussion of the results can be found by selecting the option "What it means"