Abstract
Digital elevation models are today a common part of geographic information systems and derived applications. The way of their creation is varied. It depends on the extent of area, required accuracy, delivery time, financial resources and technologies available. The first model covering the whole territory of the Czech Republic was created already in the early 1980's. Currently, the 5th DEM generation is being finished. Data collection for this model was realized using the airborne laser scanning which allowed creating the DEM of a new generation having the precision up to a decimetre. Model of such a precision expands the possibilities of employing the DEM and it also offers new opportunities for the use of elevation data especially in a domain of modelling the phenomena dependent on highly accurate data. The examples are precise modelling of hydrological phenomena, studying micro-relief objects, modelling the vehicle movement, detecting and describing historical changes of a landscape, designing constructions etc. <br><br> Due to a nature of the technology used for collecting data and generating DEM, it is assumed that the resulting model achieves lower accuracy in areas covered by vegetation and in built-up areas. Therefore the verification of model accuracy was carried out in five selected areas in Moravia. The network of check points was established using a total station in each area. To determine the reference heights of check points, the known geodetic points whose heights were defined using levelling were used. Up to several thousands of points were surveyed in each area. Individual points were selected according to a different configuration of relief, different surface types, and different vegetation coverage. The sets of deviations were obtained by comparing the DEM 5G heights with reference heights which was followed by verification of tested elevation model. Results of the analysis showed that the model reaches generally higher precision than the declared one in majority of areas. This applies in particular to areas covered by vegetation. By contrast, the larger deviations occurred in relation to the slope of the terrain, in particular in the micro-relief objects. The results are presented in this article.
Highlights
Thanks to a development of computers, geographic information systems and internet the exploitation of geographic data spread into most domains of human activities
Because it failed to show the normal distribution of height deviations, the confidence interval of 95% was used to determine the accuracy of elevation models
The results showed that despite a presence of systematic effects the models comply with the declared accuracy in both the open terrain and the areas covered by vegetation (Hubacek et al 2015)
Summary
Thanks to a development of computers, geographic information systems and internet the exploitation of geographic data spread into most domains of human activities. The first models were generated using traditional cartometric methods that were supplemented by surveying methods when the high accuracy at limited areas was required (Gallant 2000). The airborne laser scanning (ALS) is in the forefront of the methods of the elevation model production. This technology allows collecting large volumes of data covering extensive areas in relatively short time. The ALS was employed for creating the new elevation models in the Czech Republic These models, with their level of detail and accuracy, represent a new generation of geographic data. It is necessary to conduct an independent verification of their accuracy and to determine possible limitation of their use
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