Blom has many years of experience in producing high quality elevation models from LiDAR data. Almost all deliveries are preceded by manual editing where the automatic classification is corrected for errors to assure a final product with expected quality. Classification of laser data determines which laser points represent ground and which represent other objects, such as vegetation and buildings. Since the classified ground points are the foundation for the elevation model, it is important that the classification is carefully controlled.
Blom has a wide experience in collecting and editing all types of laser data. Both in larger projects, like the nationwide NNH project in Sweden or the similar NLS project in Finland, and in smaller projects with higher point densities.
Both NNH-data and NLS-data are, at their present state, only controlled with respect to gross errors; hence require additional editing to assure a high quality elevation model. Errors occur primarily in dense and low vegetation, at rapid terrain variations, along bridges and in complex urban environments. When generating elevation contours it is also important to supplement with break lines, especially at water edges.
In flood analysis errors in classification can cause severe misinterpretation. Vegetation erroneously classified as ground may be incorrectly assumed as a barrier to water flow, and missing ridges and banks might cause incorrect analysis of water spread.
The time needed for editing varies between projects and depend on which requirements there are of the final product, vegetation type and season, terrain types and quality of laser data.
If you would like to know more about editing and what is required for your product to achieve the desired quality, please contact Dag Solberg.