Background: New technologies for terrain reconstruction have increased the availability of topographic data at a broad range of resolutions and spatial extents. The existing digital elevation models (DEMs) can now be updated at a low cost in selected study areas with newer, often higher resolution data using unmanned aerial systems (UAS) or terrestrial sensors. However, differences in spatial c...

This research aims to protect Digital Elevation Model (DEM) data from piracy or counterfeiting. An invisible watermark inserted into the data, which will not considerably change value, is necessary. The proposed method involves use of two-dimensional discrete cosine transform (2D DCT), a combination 2D DCT and wavelet (DWT), Fourier DFT) in frequency domain. used include National DEM file downl...

This paper discusses the flight test results of a real-time Digital Elevation Model (DEM) integrity monitor for Civil Aviation applications. Providing pilots with Synthetic Vision (SV) displays containing terrain information has the potential to improve flight safety by improving situational awareness and thereby reducing the likelihood of Controlled Flight Into Terrain (CFIT). Utilization of D...

This paper describes a new fast and scalable parallel algorithm to compute global flow accumulation for automatic drainage network extraction in large digital elevation models (DEM for short). Our method uses the D8 model to compute the flow directions for all pixels in the DEM (except NODATA and oceans). A parallel spanning tree algorithm is proposed to compute hierarchical catchment basins to...

Elongated topographic artifacts, such as the striping production artifacts described for USGS 7.5-minute DEMs, can result in globally biased estimates of slope and aspect. As such, developing methods to reduce these artifacts and their resulting biases is important. This study presents an algorithm for the mitigation of these artifacts, using Terrain Resource Information Management (TRIM) digit...

The aim of this study is to investigate the accuracy and reliability of radargrammetric DEMs generated from RADARSAT-2 stereo pairs. Two ultrafine mode images U7 and U26 were acquired over an area in Istanbul from descending orbit, HH polarization, in SGF format. U7 and U26 were taken on August 2, 2009 and July 30, 2009 with view angles of 34.0 35.3 and 48.5 49.5 at the near–far edges, respecti...

Terrain aided positioning (TAP) is a kind of positioning method which acquires position information from the terrain elevation datum underneath the vehicle. This method has the characteristics of autonomy, allweather, anti-interference, strong stealthiness and high accuracy. It is widely used in the navigation system for various aircrafts, cruise missiles and underwater vehicles. The fundamenta...

Under increased urban settlement density, access to a high resolution (land-parcel scale) bare-earth Digital Elevation Model (DEM) is a pre-requisite for much decision support for planning: stormwater assessment, flood control, 3D visualisation, automatic delineation of flow paths, sub watersheds and flow networks for hydrological modelling. In these terms, a range of options face the DEM-build...

Calculations based on US Geological Survey (USGS) digital elevation models (DEMs) inherit any errors associated with that particular representation of topography. We investigated the potential impact of error in a USGS 30 m DEM on terrain analysis over 27 km. The difference in elevation between 2652 differential Global Positioning Systems measurements and USGS 30-m DEM derived elevations provid...