Automatic generation of hypsometric layers for small-scale maps

This paper describes a new method for hypsometric tinting for small-scale maps. The method generalises digital elevation models by removing small unnecessary details and accentuating major valleys and ridgelines. The elevation data are filtered with lower and upper quartile filters that are combined using a drainage network. The lower quartile filter is applied in valleys, delimited by the drainage network, the upper quartile filter is used elsewhere. The level of generalisation is adjusted by simplifying the drainage network with an algorithm that removes the shortest streams. The resulting hypsometric layers match the quality standards of manually generalised reference layers and are appropriate for small-scale mapping.