Abstract
To date, digital terrain model (DTM) accuracy has been studied almost exclusively by computing its height variable. However, the largely ignored horizontal component bears a great influence on the positional accuracy of certain linear features, e.g., in hydrological features. In an effort to fill this gap, we propose a means of measurement different from the geomatic approach, involving fluid mechanics (water and air flows) or aerodynamics. The particle image velocimetry (PIV) algorithm is proposed as an estimator of horizontal differences between digital elevation models (DEM) in grid format. After applying a scale factor to the displacement estimated by the PIV algorithm, the mean error predicted is around one-seventh of the cell size of the DEM with the greatest spatial resolution, and around one-nineteenth of the cell size of the DEM with the least spatial resolution. Our methodology allows all kinds of DTMs to be compared once they are transformed into DEM format, while also allowing comparison of data from diverse capture methods, i.e., LiDAR versus photogrammetric data sources.
Highlights
A lot of geomatic applications use digital terrain model (DTM) as the basis to derive other products such as cartography, hydrological features, engineering solutions, urban planning, environmental studies, time series analyses, reports, statistics, etc
In order to study the influence of the resampling method to resize the Instituto Geográfico Nacional” (IGN) digital elevation models (DEM) to the size of the Instituto Cartográfico de Andalucía” (ICA) DEM, we compute the differences in height for the two extreme cases, i.e., Quéntar
After computing the scale factor, the results obtained from the adjusted PIVEHD (APIVEHD) applied to our dataset seem to be suitable for estimating the horizontal displacement (Tables 7–9), but there is a variable that could be modified for suitable estimation yield by APIVEHD; this variable is the cell size ratio between the DEMs compared
Summary
A lot of geomatic applications use DTMs as the basis to derive other products such as cartography, hydrological features, engineering solutions, urban planning, environmental studies, time series analyses, reports, statistics, etc. It is possible for each cell in the CompDEM to be horizontally displaced in any direction, so that homologous contours cross each other as shown, where the area between homologous contours has been filled with gray color Both vertical and horizontal accuracy are important features to keep in every DEM because error in vertical and horizontal positioning could have bad consequences when, for example, computing flood risk areas. CompDEM altitude is higher than the RefDEM altitude and an urban area is flooded); the image on the bottom right shows the error due to horizontal inaccuracy (the CompRef is moved to the left and up direction and an urban area is flooded) Another example of horizontal accuracy importance comes from the ability of LiDAR data to produce a highly detailed drainage network [9] and it would be interesting to know the variation in the streams if computed with different DEM sources.
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