An automated GIS procedure for comparing GPS and proximal LIDAR elevations (original) (raw)
Related papers
Canadian Journal of Remote Sensing, 2006
High-resolution laser altimetry (lidar) is applied to geological problems such as bedrock and surficial mapping and the relationship to earth surface processes in the Fundy Basin of Nova Scotia. A "bald earth" lidar digital elevation model (DEM) is used in conjunction with field observations to map three flow units of the Jurassic North Mountain Basalt (NMB) based on contrasting terrain characteristics (slope, smoothness, and relief). The variable resistance of the flow units to erosion, documented by shatterbox experiments and down-core fracture density data, has a measurable control on incision by post-glacial consequent streams. In catchments where till cover is thick, greater surface runoff and weaker infiltration increase incision by as much as 43% for a given flow unit. Interpretation of field, petrologic, and digital topography data indicates previously unrecognized craters in the lower flow unit are the result of interaction between partially solidified lava and surface water or groundwater. Two new sets of surficial landforms have been identified that indicate ice was directed northwestward into the Bay of Fundy during the late stages of glaciation. Twice as many wave-cut terraces have been identified in the lidar DEM than previously mapped, and elevations have been extracted and compared with published values that are related to higher sea-levels at 12-14 ka. This paper demonstrates through a range of examples that the precision and enhanced resolution of lidar can improve our understanding of how landscapes form and evolve. Webster et al. 193 Résumé. L'altimétrie lidar à haute définition s'applique à des phénomènes d'ordre géologique, tels la cartographie du sousbassement rocheux ou de la surface terrestre, ainsi qu'au rapport avec les processus à la surface terrestre dans le bassin du Fundy en Nouvelle Écosse. Un modèle numérique d'élévation lidar « terre nue » est utilisé parallèlement avec des observations sur le terrain pour dresser la carte de trois écoulements basaltiques du Jurassique à North Mountain selon des traits caractéristiques divers (la pente, la régularité et le relief). Les différents facteurs de résistance à l'érosion des différents écoulements exercent un contrôle mesurable sur l'érosion verticale d'écoulements ultérieurs post-glaciaires. Dans des bassins-versants à couvert morainique épais, un plus fort ruissellement de surface et une plus faible infiltration dans le sol sont susceptibles d'augmenter l'érosion verticale pour un écoulement donné de jusqu'à 43 %. L'interprétation de données de terrain, ainsi que des données pétrologiques et topographiques numériques donne à entendre que des cratères dans l'écoulement le plus bas, jusqu'alors non constatés, proviennent de l'interaction entre la lave partiellement refroidie et solidifiée et de l'eau : soit l'eau de surface, soit l'eau souterraine. Ont été identifiés deux nouveaux ensembles de relief surfacique qui donnent à entendre que la glace se serait déplacée vers le nord-ouest pour se verser dans la Baie de Fundy pendant une phase tardive de l'âge glaciaire. Deux fois plus de terrasses coupées par l'action des vagues ont été constatées qu'il n'en était antérieurement cartographiées et des altitudes topographiques correspondant à des niveaux plus élévés de la mer il y a 12 ou 14 quatorze mille ans ont été calculées et comparées aux valeurs publiées. Ce présent travail fait voir, à travers une série d'exemples, que la précision et la très haute définition du lidar peuvent enrichir notre compréhension des processus de formation et évolution du paysage.
Modelling vertical error in LiDAR-derived digital elevation models
ISPRS Journal of Photogrammetry and Remote Sensing, 2010
A hybrid theoretical-empirical model has been developed for modelling the error in LiDAR-derived digital elevation models (DEMs) of non-open terrain. The theoretical component seeks to model the propagation of the sample data error (SDE), i.e. the error from light detection and ranging (LiDAR) data capture of ground sampled points in open terrain, towards interpolated points. The interpolation methods used for infilling gaps may produce a non-negligible error that is referred to as gridding error. In this case, interpolation is performed using an inverse distance weighting (IDW) method with the local support of the five closest neighbours, although it would be possible to utilize other interpolation methods. The empirical component refers to what is known as ''information loss''. This is the error purely due to modelling the continuous terrain surface from only a discrete number of points plus the error arising from the interpolation process. The SDE must be previously calculated from a suitable number of check points located in open terrain and assumes that the LiDAR point density was sufficiently high to neglect the gridding error. For model calibration, data for 29 study sites, 200 × 200 m in size, belonging to different areas around Almeria province, southeast Spain, were acquired by means of stereo photogrammetric methods. The developed methodology was validated against two different LiDAR datasets. The first dataset used was an Ordnance Survey (OS) LiDAR survey carried out over a region of Bristol in the UK. The second dataset was an area located at Gador mountain range, south of Almería province, Spain. Both terrain slope and sampling density were incorporated in the empirical component through the calibration phase, resulting in a very good agreement between predicted and observed data (R 2 = 0.9856; p < 0.001). In validation, Bristol observed vertical errors, corresponding to different LiDAR point densities, offered a reasonably good fit to the predicted errors. Even better results were achieved in the more rugged morphology of the Gador mountain range dataset. The findings presented in this article could be used as a guide for the selection of appropriate operational parameters (essentially point density in order to optimize survey cost), in projects related to LiDAR survey in non-open terrain, for instance those projects dealing with forestry applications.
Influence of Vegetation, Slope, and Lidar Sampling Angle on DEM Accuracy
Photogrammetric Engineering and Remote Sensing, 2006
Detailed GIS studies across spatially complex rangeland landscapes, including the Aspen Parkland of western Canada, require accurate digital elevation models (DEM). Following the interpolation of last return lidar (light detection and ranging) data into a DEM, a series of 256 reference plots, stratified by vegetation type, slope and lidar sensor sampling angle, were surveyed using a total laser station, differential GPS and 27 interconnected benchmarks to assess variation in DEM accuracy. Interpolation using Inverse Distance Weighting IDW resulted in lower mean error than other methods. Across the study area, overall signed error and RMSE were ϩ0.02 m and 0.59 m, respectively. Signed errors indicated elevations were overestimated in forest but underestimated within meadow habitats. Increasing slope gradient increased vertical absolute errors and RMSE. In contrast, lidar sampling angle had little impact on measured error. These results have implications for the development and use of high-resolution DEM models derived from lidar data.
Accuracy assessment of lidar-derived digital elevation models
The Photogrammetric Record, 2008
Despite the relatively high cost of airborne lidar-derived digital elevation models (DEMs), such products are usually presented without a satisfactory associated estimate of accuracy. For the most part, DEM accuracy estimates are typically provided by comparing lidar heights against a finite sample of check point coordinates from an independent source of higher accuracy, supposing a normal distribution of the derived height differences or errors. This paper proposes a new methodology to assess the vertical accuracy of lidar DEMs using confidence intervals constructed from a finite sample of errors computed at check points. A non-parametric approach has been tested where no particular error distribution is assumed, making the proposed methodology especially applicable to non-normal error distributions of the type usually found in DEMs derived from lidar. The performance of the proposed model was experimentally validated using Monte Carlo simulation on 18 vertical error datasets. Fifteen of these data-sets were computed from original lidar data provided by the International Society for Photogrammetry and Remote Sensing Working Group III/3, using their respective filtered reference data as ground truth. The three remaining data-sets were provided by the Natural Environment Research Council's Airborne Research and Survey Facility lidar system, together with check points acquired using high precision kinematic GPS. The results proved promising, the proposed models reproducing the statistical behaviour of vertical errors of lidar using a favourable number of check points, even in the cases of data-sets with non-normally distributed residuals. This research can therefore be considered as a potentially important step towards improving the quality control of lidar-derived DEMs.
The Journal of Island and Coastal Archaeology, 2019
The dynamic environmental history and relative sea level (RSL) changes experienced on the Northwest Coast of North America during the early post-glacial period and the early Holocene resulted in significant archaeological visibility challenges for prospection of early coastal archaeological sites. This study offers an integrated methodological approach in support of locating palaeo-coastal sites by combining: (1) geo-morphic interpretation of landscape attributes captured by LIDAR (Light Detection and Ranging) mapping; (2) GIS-based archaeological site potential mapping; and (3) local RSL history. The RSL history for the study site (Quadra Island, British Columbia, Canada) shows notable regression over the past 14,300 years from a highstand of at least 197 m resulting from post-glacial isostatic rebound. Late Pleistocene and early Holocene palaeo-shorelines are found inland from, and elevated above, modern sea level and represent key areas for archaeological prospecting. Bare-earth Digital Terrain Models (DTMs) derived from the LIDAR dataset were interpreted to identify palaeo-shorelines at 10 m and 30 m above mean sea level. A GIS-derived map was created to identify regions of high archaeological potential. Field validation suggests that this integrated methodology provides a promising approach for archaeological prospection that could be applied to other post-glacial coastal settings. ARTICLE HISTORY
Characterizing the error distribution of lidar elevation data for North Carolina
International Journal of Remote Sensing, 2011
Spatial data quality is a paramount concern in all geographical information systems (GIS) applications. Existing standards and guidelines for spatial data commonly assume the positional error is normally distributed. While non-normal behaviour of the error in digital elevation data has been observed in previous research, current guidelines for digital elevation data still assume that the errors for observations in open terrain are normally distributed. This research employed an accuracy assessment dataset from a substantial lidar data collection effort, the North Carolina Floodplain Mapping Program. Strong evidence was found that the vertical error of lidar elevation data is not normally distributed and that both major and minor outliers are very common. Of the five land cover types considered, only the distribution for urban areas approximated a normal distribution, even though these observations were generally much less accurate than those for open terrain. No influence of slope on the occurrence of non-normal behaviour in the distributions was found. The RMSE z (root mean square error) statistic used to characterize the fundamental accuracy of digital elevation data was found to be very sensitive to the occurrence of outliers, questioning its use in current guidelines. *
Accuracy Assessment of Lidar Data Using Geomatic Approaches
2013
The fast development in Remote Sensing technology with various sources of data especially LiDAR (Light Detection And Ranging) images promote the ability of using data , but the accuracy of produce Maps issue always need to be evaluate. So the main aim of this research is to evaluate the accuracy of using elevation data for various techniques, such as Photogrammetry and remote sensing techniques then comparison with traditional filed surveying using DGPS total station and level instrument. LiDAR data gives accurate elevation therefore; 3D model can be obtained from LiDAR data which can be used in many applications such as civil engineering and surveying engineering, etc. In this research University of Technology has been chosen as case study area, and many Geomatic approaches executed such as extracted height of features from field surveys using Total Station and comparison with the heights extracted from LiDAR data. According to the results analysis it can be stated that the elevati...
A comparison of digital elevation models generated from different data sources
Geomorphology, 2009
It can be challenging to accurately determine the topography of physically complex landscapes in remote areas. Ground-based surveys can be difficult, time consuming and may miss significant elements of the landscape. This study compares digital elevation models (DEMs) generated from three different data sources, of the physically complex Narran Lakes Ecosystem, a major floodplain wetland ecosystem in Australia. Topographic surfaces were generated from an airborne laser altimetry (LiDAR) survey, a ground-based differential GPS (DGPS) survey containing more than 20,000 points, and the 9″ DEM of Australia. The LiDARand DGPS-derived data generated a more thorough DEM than the 9″ DEM; however, LiDAR generated a surface topography that yielded significantly more detail than the DGPS survey, with no noticeable loss of elevational accuracy. Both the LiDAR-and the DGPS-derived DEMs compute the overall surface area and volume of the largest floodplain lake within the system to within 1% of each other. LiDAR is shown to be a highly accurate and robust technique for acquiring large quantities of topographic data, even in locations that are unsuitable for ground surveying and where the overall landscape is of exceptionally low relief. The results of this study highlight the potential for LiDAR surveys in the accurate determination of the topography of floodplain wetlands. These data can form an important component of water resource management decisions, particularly where environmental water allocations for these important ecosystems need to be determined.
Experimental Verification of the Possibility of Using Lidar Data from a Forested Area in Archeology
2015
One of the most progressive method for spatial data acquisition is Airborne Laser Scanning (ALS), widely called LIDAR (an acronym of LIght Detection And Ranging). Its biggest advantage is that the laser beam can pass through vegetation so we can create a Digital Terrain Model (DTM) also in forrested areas where e.g. photogrammetry fails due to dense canopy cover. One of the most significant INSPIRE principles says “spatial data should be collected only once and kept where it can be maintained most effectively”. That is reason we decided to test whether or not LIDAR data gathered for forestry can be used in archeology.