Reduction of measurement data before Digital Terrain Model generation vs. DTM generalisation

Modern data-acquisition technologies provide large datasets. Such datasets are often cumbersome for rational processing, and their processing is time consuming. Therefore, there are several methods that can enable the reduction of the dataset size. One of them is generalisation of the Digital Terrain Model (DTM) or the reduction method within the initial processing of measurement data. Another method can be the Optimum Dataset (OptD) method. This paper presents two approaches towards decreasing the Light Detection and Ranging dataset. The first approach is based on the process of DTM generalisation, the second one is based on the application of the OptD method. The reduced datasets were used for isoline map creation depicting the overflow land in open-pit mining. It was proved that the reduction needs to be planned deliberately and that the degree of reduction should be performed in a way that allows to maintain the characteristics of the terrain.