An investigation into the precision of a digital camera

Civil Engineering and Geoscience

The variants of an LOD of a 3D building model and their influence on spatial analyses

The level of detail (LOD) of a 3D city model indicates the model's grade and usability. However, there exist multiple valid variants of each LOD. As a consequence, the LOD concept is inconclusive as an instruction for the acquisition of 3D city models. For instance, the top surface of an LOD1 block model may be modelled at the eaves of a building or at its ridge height. Such variants, which we term geometric references, are often overlooked and are usually not documented in the metadata. Furthermore, the influence of a particular geometric reference on the performance of a spatial analysis is not known.In response to this research gap, we investigate a variety of LOD1 and LOD2 geometric references that are commonly employed, and perform numerical experiments to investigate their relative difference when used as input for different spatial analyses. We consider three use cases (estimation of the area of the building envelope, building volume, and shadows cast by buildings), and compute the deviations in a Monte Carlo simulation.The experiments, carried out with procedurally generated models, indicate that two 3D models representing the same building at the same LOD, but modelled according to different geometric references, may yield substantially different results when used in a spatial analysis. The outcome of our experiments also suggests that the geometric reference may have a bigger influence than the LOD, since an LOD1 with a specific geometric reference may yield a more accurate result than when using LOD2 models.Urban Data Scienc

Icesat full waveform altimetry compared to airborne laser altimetry over the Netherlands

Since 2003 the spaceborne laser altimetry system on board of NASA’s Ice, Cloud and land Elevation Satellite (ICESat) has acquired a large world-wide database of full waveform data organized in 15 products. In this research three products are evaluated over The Netherlands. For this purpose the raw full waveform product, the derived Gaussian decomposition product and the global land evaluation product are compared to laser data from the Dutch national airborne laser altimetry archive AHN. Using the CORINE land cover 2000 database allows us to compare ICESat to AHN elevation profiles with respect to the land cover classes forest, urban, bare land/low vegetation and water. This comparison shows that a large average height difference of 5.7 m occurs over forest, while much smaller differences of 1.24 m over urban areas, of 0.43 m over bare land/low vegetation and of 0.07 m over water are found. The reason for this large difference over forests is that the standard processing of NASA does not take the position of the last Gaussian mode of the waveform into account. Incorporating results from a full waveform processing procedure allows us to determine improved ICESat profiles. Comparing the improved profiles shows that the average difference with the AHN profiles over forest is reduced to -0.38 m, while the average differences for the other land cover classes do not exceed -0.75 m. Encountered limitations are discussed in the conclusions.Remote SensingAerospace Engineerin

ICESat Full-Waveform Altimetry Compared to Airborne Laser Scanning Altimetry Over The Netherlands

Since 2003, the full-waveform laser altimetry system onboard NASA's Ice, Cloud and land Elevation Satellite (ICESat) has acquired a worldwide elevation database. ICESat data are widely applied for change detection of ice sheet mass balance, forest structure estimation, and digital terrain model generation of remote areas. ICESat's measurements will be continued by a follow-up mission. To fully assess the application possibilities of the full-waveform products of these missions, this research analyzes the vertical accuracy of ICESat products over complex terrain with respect to land cover type. For remote areas, validation of individual laser shots is often beyond reach. For a country with extensive geo-infrastructure such as The Netherlands, excellent countrywide validation is possible. Therefore, the ICESat full-waveform product GLA01 and the land elevation product GLA14 are compared to data from the Dutch airborne laser altimetry archive Actual Height model of the Netherlands (AHN). For a total population of 3172 waveforms, differences between ICESat- and AHN-derived terrain heights are determined. The average differences are below 25 cm over bare land and urban areas. Over forests, differences are even smaller but with slightly larger standard deviations of about 60 cm. Moreover, a waveform-based feature height comparison resulted in feature height differences of 1.89 m over forest, 1.48 m over urban areas, and 29 cm over low vegetation. These results, in combination with the presented processing chain and individual waveform examples, show that state-of-the-art ICESat waveform processing is able to analyze waveforms at the individual shot level, particularly outside urban areas.Remote SensingAerospace Engineerin

3D Pilot: Eindrapport werkgroep Aanbod van 3D geo-informatie

OTB ReseachOTB Research Institute for the Built Environmen

3D pilot: Managementsamenvatting: impressie van een jaar samenwerken

OTB ResearchOTB Research Institute for the Built Environmen

Establishing a reference model for 3D geo-information in the Netherlands

This paper presents the work in progress of a research project that aims at establishing a reference model for 3D geoinformation in the Netherlands by extending existing 2D and 3D national and international standards.Department of GIS TechnologyOTB Research Institute for the Built Environmen

Towards a 3D geo-information standard in the Netherlands

This paper presents the ongoing research project in The Netherlands in which a large number of stakeholders are realising a 3D testbed based on selected use cases and test areas. The findings of the project will result in a Proof of Concept for a 3D Geoinformation standard and a 3D data infrastructure in The Netherlands compatible with international (e.g. CityGML) and national standards.OTB onderzoekOTB Research Institute for the Built Environmen

Slimme 3D indoormodellen ter ondersteuning van crisismanagement in grote openbare gebouwen

In dit project richten wij ons op het gebrek aan up-to-date 3D indoormodellen voor een groot aantal openbare gebouwen. Deze modellen zijn voor vele stakeholders, maar vooral voor organisaties die zorg moeten dragen voor het managen van de veiligheid van openbare gebouwen, inclusief de BHV (Bedrijfshulpverleners), de brandweer en de veiligheidsregio’s, cruciaal. De enige ruimtelijke indoorgegevens, die momenteel voor de meeste gebouwen beschikbaar zijn, zijn 2D bouwtekeningen of ontwerp-BIMs (Building Information Models) voor de nieuwe gebouwen. Deze geven de staat van het gebouw ‘zoals ontworpen’ weer, die kan verschillen van de staat van het gebouw ‘zoals gebouwd’ of ‘zoals het is’. Tijdens operaties in de hulpverlening is kennis over verbouwingen (bijv. verlaagde plafonds of verhoogde vloeren), hoogte van de kamers en gangen en aanwezig meubilair van cruciaal belang voor brandbestrijders. Dergelijke informatie kan alleen verkregen worden via een up-to-date 3D indoormodel van het gebouw. Het project richt zich op verscheidene thema’s, die elders afzonderlijk behandeld zijn, maar nooit als één geheel. Het project streeft er naar een brug te slaan tussen onderzoek op het gebied van 3D indoorreconstructie variërend van puntenwolken, 3D indoormodellen (geometrie, semantiek en topologie) en 3D indoornavigatie ten behoeve van gebruikers. Op dit moment bestaat er geen procedure voor halfautomatische of automatische 3D reconstructie uit puntenwolken Puntenwolken zijn de data die vergaard worden nadat een apparaat een scan heeft uitgevoerd van alle hoeken en gaten van het gebouw. De puntenwolk wordt vertaald in een uitgebreid 3D-model dat verder kan worden onderverdeeld of geaggregeerd om verschillende gebruikers en activiteiten in crisissituaties te ondersteunenUrbanismArchitecture and The Built Environmen