# Tagged Questions

acronym for digital terrain model -- a data structure providing elevation (or some other geographical variable) as an empirical function of horizontal position

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### What is the difference between DEM, DSM and DTM?

I am listing some of the acronyms used in our work and had to stop to think about whether to list these together or separately. In some circles they are synonymous, in others they have distinct ...
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### How to calculate terrain Curvature?

I have an elevation raster and I would like to get some basic terrain variables, such as slope, ruggedness, aspect or curvature. The problem is that I don't seem to have the possibility to calculate ...
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### How to calculate the total ascent along a path

I am working on a series of footpath routes and have been asked if it possible to calculate the total ascent that a walker would have climbed if the travelled along each route? I know that it is ...
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### Elevation profile sample point algorithm

In generating an elevation profile, samples from the underlying raster must be taken. If the objective is to create a profile of maximum quality, how should the locations of sample points be ...
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### What is the smallest contour interval possible when derived from a DTM?

I am converting a 2m DTM to contours, and would like to have the smallest interval possible. Is there a theoretical limit, or even a rule of thumb for defining contour intervals based on the ...
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### How can I convert a DEM into areas of “flatness”, with an arbitrary fill/cut to area ratio?

I want to find areas of relative "flatness" in a DEM. How can I find flat areas? I want to find a neighbourhood of contiguous cells that have an elevation variance that is within a certain ...
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### How to change DEM's gradient colour?

I'm a newbie about GIS. I'm from Italy and I've got a *.tif file of my region. I've loaded it has raster but I have a question: The dem has a gradient colour magenta. How change this colour to ...
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To go a little bit further than the semantic question regarding DEM/DTM/DSM, I'd like to know if there is a free (of charges and use) DTM datasets? And what about resolution? As far as I know,only ...
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### How to find upstream - lateral and downstream zones around urban areas?

I've a DTM and a shapefile of built-up areas. For a fire risk model, I've to find (within a defined buffer zone) two zones around built-up areas: one that is above/higher and lateral and the other ...
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### Where to acquire elevation data for UK?

I'm looking for digital elevation data for UK. Does anybody know if there is a good service providing data for free that are of better accuracy than ASTER-DEM that is around 30m and if not what is the ...
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### Extra lines in Sketchup DTM when using stamp tool

I have a DTM in Sketchup. I am trying to use the stamp tool to make a level area on which to build a building. However, when I use the stamp tool lots of extra lines appear on the DTM seemingly at ...
1k views

### River drainage basin boundary

I'm looking for a set of outlines of the river basins in the UK - I don't need a particularly detailed or highly accurate map - just a map saying point X will drain into the Thames or point Y will ...
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### Profile plot trouble in Grass GIS

I'm new to Grass and GIS environments in general, and I recently faced a problem when trying to get the profile plot from a DTM. When I draw the transect, instead of the plot, I get the following ...
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### How to limit a specific area in order to have a topographic 3D map using MatLab?

I am using MatLab, I want to build a topographic 3D map, I am following this guide, I have been doing the steps listed on the section Draping Geoid Heights over Topography, and I do not have any ...
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### Driver Error : DTM to Raster using GDAL_GRID

I am looking to interpolate a DTM (eventually over 4,000 DTMs) that is in a personal geodatabase format. I would like to do this in as few step as possible, eventually writing a batch script to do ...
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### What is the method for finding the percentage of common cells among 2 or more DTMs for the same area?

I have a study area and 6 different DTMs for that area from different sources and I would like to know the percentage of pixels with the same value. I suppose I will have to extract some statistic and ...
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### What is the highest obtainable resolution of FREE elevation data in the UK?

I am seeking closure with this question guys. I am aware of various sources of free elevation data ~30+ m, and I have been searching for higher resolution FREE data for a while now. This already ...
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### Where to acquire free elevation data for Thailand/Bangkok?

I am in the process of writing my thesis on flood hazard preparedness and forecasting in South East Asia, specifically Thailand. My analysis requires a medium resolution (even better, high resolution) ...
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### How to get the altitude of the vector shapes from DTM raster layer?

I have a vector layer containing thousands of vector shapes/polygons and a raster layer with DTM. Every shape has its own OBJECTID in attribute table. I would like to get the altitude of every shape, ...
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### Polyline ZM: automatic vertex height errors correction

Paolo I've got many rivers (polylines ZM) with a lot of height errors in Polylines 'vertices. Vertices' Z errors are not all equal in height (i.e. they are not all at zero height). I must create a TIN ...
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### Is there any accuracy difference between standard DTM editing tools like DT Master and automatic removal of artefacts using ERDAS?

I would like to know whether there is any accuracy difference while editing DTM points using standard photogrammetry software like Inpho DT Master and automatics removal of artefacts in ERDAS imagine. ...
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### Correlation and terrain databases [duplicate]

I would like to know what kind of computation I could perform on a terrain database. I'm making terrain for VBS2 from raw data (shp files and DTM Elevation files) and then I'd like to be able to check ...
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### How to transform a DEM to a cartesian coordinate system?

I am using the script r.inund.fluv. I run the script with all the required parameters and it produced a lot or errors. I emailed the author of the script and he said that "I think you are not ...