SRTM Processing If you want know what a DEM, DSM or DEM is, please visit the. First the processing of an enhanced SRTM Digital Surface Model (DSM) is explained. This step is also necessary for the following processing of a Digital Terrain Model (DTM) on the basis of OpenStreetMap vector data. For detailed information see the. The explored the structure of the earth surface in February 2000. The earth surface height was recorded between 60°N and 56°S.
The data is available in 1.1 deegree (SRTM-1) for the USA and 3.3 degree (SRTM-3) tiles for the rest of the world. The resolution is for SRTM-3 three-arc-seconds, which is about 90 meters. The SRTM data (Level 2.1, the most advanced processing state) can be downloaded. SRTM Digital Surface Model (DSM) Processing Due to the side-looking radar technique used by SRTM voids occur in mountainous regions as you see on Figure 1. Fig.1: Voids resulting from side looking radar technique (left) and void pixels in the Alps are presented as black pixels (right). These voids have the value '-32.768' and were filled with DEM data provided by Jonathan de Ferranti for the OpenDEM project. Many thanks for that.
The data could be downloaded from the. Beside voids in mountainous regions, voids occur also near water bodies. A watermask was already applied for Level 2.1 SRTM data by the USGS. These voids were filled by a 3.3 Matrix with the mean value (zero values were ignored). The process was performed 3 times inn order to eliminate all voids. The data can be downloaded in the under the. SRTM Digital Terrain Model (DTM) Processing The SRTM mission mapped the structure of the earth´s surface including builtings and vegetation.
OpenStreetMap data was used to correct the height values for forested and built up areas. The resulting DTM is only an approximation, depending on many factors: 1. Time: The SRTM dataset is from February 2000 and many changes have occured since this time, especially in the built up regions 2. Quality of the OSM data: Completeness & accuracy 3. Accuracy of the SRTM dataset 4. Structure of the built up areas 5. Development stage and type of the forested areas At first all land areas with zero values were set to a value of 1.
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This was done for a better visual discrimination between land and sea areas. 2: Land values set to 1 (left) and the original dataset on the right for the German North Sea Coast (zeros in blue). The OSM land tiles can be downloaded. If the server is down, the data could also be downloaded from this server (stamp 3/2010).
For the built up and forested areas a computed value was subtracted. The computation of the values is described in detail in the following Built up areas are in general very heterogeneous. The question was: is itpossible to enhance the dataset by a subtracted constant value for the built up areas? The following OSM tags were used to identify the built up areas: highway: pedestrian highway: residential highway: livingstreet man made:building Forested areas should be not be as heterogeneous through as a more homogeneous canopy cover. But the recording of the data was in February.
So in the northern hemisphere the structure of the forested areas was quite heterogeneous for the deciduous forests. The radar backscatter was reflected from the trunks and branches due to the absence of the leaves.
Unfortunately, also for the coniferous forests the structure was not as homogeneous as expected. The following OSM tags were was used to identify the forested areas: natural: wood landuse: forest Whereas natural:wood is a tag used for natural woods the tag landuse:forest is used for forested woods.
Please be aware that the usage varies from country to country. The vector data was intersected with the SRTM raster data and two datasets were derived with the landuse classes of forest and urban.
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To compare these landuse classes with bare soils, also OSM vector data associated with moderate vegetation landuse:meadow and landuse:farm were intersected with the SRTM dataset. Difference images from SRTM and an official 5 meter Digital Terrain Model were computed (vertical RMS error. Cologne Region Flat Cologne-Bonn Bay with the greater Cologne urban area and surrounding rural areas (122.625 Pixels). Ruhr Basin Old metropolitan region with old coal mining areas and renaturalisation (54.579 Pixels). Rhineland Slate Mountains Forested mountainous area. Pkunzip freeware for windows 7.
(262.171 Pixels) Fig. 3: built-Up areas were marked in pink and forested areas were marked in green (click to enlarge).
Have a look at the original data: Table 1: Results of the computed difference images for the three test regions.
Digital Terrain Modelling (DTM) If your customer deliverables includes a Digital Terrain Map (DTM), then 3DReshaper is the tool of choice for easy to use ground extraction, contour mapping, and breaking line extraction. Ground Extraction The Ground Extractor tool in 3DReshaper is the fastest way to get your DTM directly from a point cloud. The tool processes automatically the point cloud in order to obtain a clean and accurate mesh of the terrain.
It detects vegetation, cars, road signs, buildings, etc. And is able to find all the points located on the ground.
Color along a direction Once you have the ground mesh, you will be able to color it along a direction so that the elevation changes are easier to see. Contour Lines Use also 3DReshaper to compute Contour Lines and either create a report or export them as.DXF to one of your other tools. Breaking Lines Massively extract streets, sidewalks or other items using the Extract Breaking Lines tool in 3DReshaper.
Automatically find the edges of contours, both convex and concave and adjust the extraction sensitivity, trim, extend, chain or edit your contours to precisely dial in the contours you want.
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FlashMNT 5.0 is a tool that allows the creation of a Digital Terrain Model and 3D computations. From points and/or breaklines, create a DTM, then use the various fonctions of FlashMNT Size: 1.98 MB Whether you want to get your topographical map with contours and 3D terrain model. Size: 1000 KB Section creation & quantity calculations. Size: 0 KB Create a terrain mesh from a set of unordered points, lines and polylines.
Size: 1.5MB Real time 3D visualization of terrain model, and DTM analysis Size: 17.2 MB Terrain for Rhino is a terrain modeling plug-in for Rhinoceros (commonly known as Rhino). This plug-in gives Rhino the ability to create a terrain mesh from a set of unordered points. Size: 2.25 MB Digital Terrain Model in description. (Signal Propagation, Loss, And Terrain analysis software) is useful for visualizing terrain and performing Longley-Rice path loss and coverage prediction using the Irregular Terrain Model. Size: 555 KB It uses Digital terrain elevation data for automatic extraction of path profile between an emitter and a receiver. This data is added to system, environmental and statistical parameters to feed the Ir. Size: 963 KB Projectable point sets occur - for example - in a Digital Terrain Model or a Digital Elevation Model.
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D# implements exact arithmetic for ultimate robustness. You can easily visualize the triangulated. Size: 211.82K TerrainCAD is a terrain generation, editing and modeling software. Powered by TerrainLib, TerrainCAD contains fast and robust algorithms to create and modify terrain meshes in no time.
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The capabilitie. Size: 4.68MB Terrain is a handy application that allows you to generate terrain maps and note specific points on the terrain. The program is a useful tool for the land surveyors that need to add notes and to adjus. Size: 14.9 MB MrMesh3D is an computer software that generates a tridimensional Terrain model as a regular squared mesh. MrMesh3D imports pictures, text files, dxf polylines or powercadd export data text files and e.
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