Macey, Howard Francis (2010) Accuracy assessment of onshore digital elevation models using RTK GPS. (MSc(R) thesis), Kingston University, .

Abstract

A Digital Elevation Model (DEM) typically represents the height of the Earth's surface or terrain and is usually derived from photogrammetry, field survey and airborne technologies. There are a variety of applications that DEMs are ideally suited for, ranging from topographic mapping, 3D terrain visualisation and orthorectification of photographs to solving real world problems such as viewshed analysis and flood modelling. The main aim of the research project was to undertake an assessment of Maltese DEMs and critically evaluate the factors that affect their accuracies and a number of subsequent objectives were created from this. One of the main areas of focus was to compare the height values of DEMs against highly accurate cm level survey data collected using Real-Time Kinematic (RTK) GPS. In addition, the impact of terrain slope, land cover, DEM resolution and interpolation algorithm were investigated to see if these factors had an impact on accuracy. The research was undertaken in Mellieha in the Northern part ofthe Island of Malta and suitable study zones were defined for data collection. Geographical Information Systems (GIS) were used to spatially model and analyse the terrain whilst Microsoft Excel and Access were used to manipulate and process the attribute data. A form of relative analysis was undertaken to assess the internal accuracies ofthe DEMs. The main finding was that the currency of the DEMs caused accuracies to decrease because in many areas the terrain had changed significantly. The interpolation methods produced some variable results due to the irregular distribution of points used in the generation of the DEMs. In addition, the research found that there was no single factor that completely influenced the accuracy of DEMs. There was a slight correlation between DEM resolution and slope in relation to accuracy although this was not particularly significant and there was some evidence that land cover had some influence.

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