Digital Elevation Model (DEM), which could be a Digital Terrain Model (DTM) or a Digital Surface Model (DSM).

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1answer
235 views

How to convert accuracy of DEM from 5 decimal places to 2

I had a csv dataset comprising of regular points containing elevation "z-values". I interpolated this using ESRI´s spatial analyst using the IDW method to produce a continuous raster surface. I set ...
2
votes
1answer
284 views

Conversion of ASTER GDEM data for CFD Analysis

I need to do a computational fluid dynamics (CFD) analysis of wind over a large area of land. I have obtained the necessary tiles from the ASTER GDEM data set (in .tif format) and was wondering how I ...
6
votes
2answers
5k views

Correct way to create a DEM from point data in csv files

I know this might seem a somewhat general question, but I have to start somewhere. I have a lot of csv files which contain point data containing height, aspect and slope measurements at a resolution ...
3
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2answers
1k views

1'' DHM: Hillshade is too rough - how to “generalize”?

I got this hillshade from my DHM (I used the hillshade-module from qgis). For my purpose there is too much relief detail (roughness). How can I get rid of this in QGIS or GRASS? Thanks! Martin
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1answer
790 views

Why does QGIS Profile from Line tool give me the same value for every point?

I'm trying to make an elevation profile with QGIS's Profile from Line plugin. But when I do, the resulting points all have the same value: -32,767. I'd like to know what I'm doing wrong. My elevation ...
6
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1answer
600 views

How do I find least cost path over a DEM based on slope magnitude and direction?

What sort of algorithms can I use to find a least cost path through a DEM where it costs more to traverse a cell going downhill or uphill than it does to follow the contour of the land? All the ...
3
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1answer
161 views

Change ellipsoid reference for altitude in a DEM

I have DEM data stored as RGF93 (Lambert-93) for lat/lon and NGF-IGN69 for altitude. I'm trying to change the reference ellipsoid for the elevation data (ultimately to NTF, but WGS84 would be fine to ...
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0answers
459 views

How to calculate Solar Radiation falling on vertical surfaces using DEMs and ArcGIS?

I am using ArcGIS10 Area Solar Radiation tool to calculate irradiation on horizontal surfaces (building roofs) but need to do the same for vertical surfaces (building facades). Any ideas on how to do ...
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0answers
199 views

slope and mosaic datasets

I was wondering if anyone has had any experience with combining multiple DEM’s into a mosaic dataset. I am working with several DEM’s and need to convert them to slope. I’m having an issue with ...
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1answer
3k views

How can I convert SRTM data to DEM or DTED?

i am working on a project which is not commercial and i need some digital elevation data for visualization. in net i have found a link and i have downloaded .asc data from following link.. SRTM Data ...
4
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1answer
499 views

Which interpolation method is the most suitable for DEMs?

Which interpolation method is the best suitable for hill/valley areas and normal ground with undulations and rivers? When working with Aster 30mX30m DEMs, which method will give the most realistic ...
1
vote
1answer
450 views

How to create a profile with profile points at discrete altitude intervalls, e.g. each 10 m

In both SAGA and QGIS theres a profile-from-line-function that does a nice job of creating profiles. But there's no way to control the altitude spacing. Any ideas for workflows that would allow me ...
13
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7answers
779 views

How to generate a random but believable digital elevation model?

Is there a way to generate a DEM, programatically or otherwise (arcpy or R?), that will feed into ArcGIS for further spatial analysis? Perhaps this needs to be broken down into smaller incremental ...
3
votes
2answers
5k views

Replacing Raster Values in Ras1 with Ras2

I have two rasters Ras1 and Ras2. I want to change the Ras1. In Ras1, there are few areas, lines, points I am interested having nodata cells and wrong data cells.(limited to interested areas only ...
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vote
2answers
914 views

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, ...
3
votes
1answer
281 views

Looking for Fortran code calculating drainage basin area

I am working in a project of glacier mass balance. For my project I want to integrate the area of the drainage basin in a glaciological system model (GSM). As the drainage area changes with time due ...
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vote
1answer
636 views

Help with technique to create contours from ASTER DEM in Phnom Penh, Cambodia

I have the ASTER version 2 DEM of Cambodia. I want to use it to create 1m contours of Phnom Penh, Cambodia. If anyone has this already please let me know. Now, onto the problems: I am using ArcGIS ...
5
votes
2answers
366 views

Seeking commercial web service for LIDAR/DSM data in USA

I apologize for not knowing all the proper terminology to ask this question. I am seeking a commercial service for providing pay-per-use high resolution elevation data in North America. It must come ...
7
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2answers
2k views

Can shaded relief be “blended” with DEM colour ramp in ArcGIS to produce a more visually dramatic result?

Not being able to use true transparencies with ArcGIS colour ramps where only solid colours are allowed has me always wondering about how to improve the look of the surface in my maps without ...
4
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2answers
5k views

Viewing .las format LIDAR data in QGIS?

Is there an easy path to visualizing this LIDAR data? I have QGIS, and some USGS LIDAR data in (.las) format downloaded from http://lidar.cr.usgs.gov/ . This means I have both the (.las) and ...
2
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0answers
478 views

GDAL tiling DTED (dt2) dataset as gdal2tiles for 3D Maps

i am searching some webgl technologies to create 3d map with digital elevation data. for web tech. i have found ReadyMap SDK to create 3d map from TMS... in ReadyMap for elevation data it uses sth ...
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3answers
2k views

How to convert raster data into regularly sampled points?

I am wondering if there's another way to convert raster data (ex: DEM) into regularly sampled points. I've used Raster to Point under ArcToolbox previously, but if the raster data is huge, that's a ...
8
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4answers
5k views

How to 'burn' a stream network into a DEM layer in ArcGIS 10?

I am working on a DEM that in an area where there is little relief. I would like to 'burn' the river network into the DEM so I can calculate flow accumulation and flow length accurately. I am using ...
2
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2answers
493 views

batch create DEM from contour maps (open source)

I have around 100 shapefiles of contours (1m interval) that I need to turn into DEMs; Is there a way to batch create these mde from contour lines? Using open source preferably.
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votes
2answers
2k views

How to use NASA Digital Elevation model data?

I've heard it is possible to use NASA elevation model to determine approximate elevation at (lat;lng) point. This might be really useful for my upcoming project since Google Elevation API has weird ...
12
votes
5answers
8k views

Is it possible to make a DEM from contours in QGIS?

Is it possible to make a DEM from contours in QGIS? I have a shp file (contours) and their heights, can I use QGIS for produce a DEM without using GRASS? I find this creating a dem from contours but ...
5
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1answer
339 views

How do I get the upstream distance to all points in a DEM from a single downstream point?

I want to get the upstream distance to all points in a DEM from a single downstream point. The goal is to create a "downstream distance to a point grid". This then would allow me to create "distance" ...
7
votes
2answers
2k views

How to build an artificial 'dam' across a river?

I have a DEM. Created all files related to watershed including accumulation, direction, streams etc... I'm stuck creating a dam. I request you to please let me know how to build an artificial 'dam' ...
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2answers
128 views

Finding Two locations with a conditional search on DEM

I want to find two locations H difference in elevation between two locations on a DEM. Ex: point A and B are my output after search on DEM. conditions are (1)buffer R distance around point A and (2) ...
8
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2answers
992 views

Extract the area of a DEM above where 60% of the region lies?

I have a DEM of a mountainous region. I'd like to extract the areas of the DEM above which 60% of the total DEM area lies. So, essentially I'd like to extract the areas representing upper portions of ...
6
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1answer
345 views

Problems creating TIN from British Columbia DEM data

Is anyone familiar with creating a TIN using ArcGIS9.3 and British Columbia DEM data (.GEN files)? I can't figure out how to get the breaklines to work during the creation of the TIN. Using ...
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2answers
2k views

Converting ASCII grid/NTF to SRTM/DEM

I want to use the Ordnance Survey Land-Form Panorama product in some software called Maperitive, which can read custom SRTM DEM files. The data is provided in the following formats: DXF [Contours] ...
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votes
4answers
4k views

Can I convert ESRI Grid (DEM) raster to USGS DEM?

There is a tool for DEM to Raster in ArcGIS but I need to convert my ArcGIS DEM rasters (mostly LiDAR) into USGS DEM. The idea is to import this DEM into Sketchup and create a "sandbox" TIN surface ...
13
votes
2answers
1k views

Good practice for generating contours from a DEM

We have just received a large set of DEMs at work and I would like to generate contours from them. The DEMs have a resolution of 1m and a size of 1kmx1km. Output from gdalinfo: Driver: ...
6
votes
3answers
5k views

How to use SRTM Global DEM for Slope calculation?

I have downloaded SRTM GDEM (~90 km resolution). I am using ArcGIS 10. I have tried to use spatial analyst to compute for slope. However, I can not compute for the slope. The output values has only ...
6
votes
2answers
857 views

FOSS method to split raster into smaller chunks

I have a raster (USGS DEM actually) and I need to split it up into smaller chunks like the image below shows. That was accomplished in ArcGIS 10.0 using the Split Raster tool. I would like a FOSS ...
4
votes
1answer
621 views

Obtaining a contour as a single polygon in ArcGIS?

I have a DEM that I want to retrieve a single contour polygon from at a given elevation. I can use the Contour tool to obtain a series of polylines at a given elevation by setting the contour interval ...
6
votes
3answers
1k views

How to find the elevation differences between adjacent pixels in ArcGIS?

Is there a way to determine what the difference in elevation is between two adjacent pixels? I am using an SRTM DEM to map faults. I am using the vertical error (>16m) as a criterion for the ...
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3answers
5k views

How to smooth a DEM?

I have a SRTM DEM and I want to create a shaded relief from it. I created the shaded relief in GRASS and the result is very nice, but a little rough becouse the area is near flat and the DEM is 90m in ...
5
votes
1answer
349 views

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 ...
2
votes
1answer
563 views

Read .DEM (USGS) FIles with C#

I have a huge number of .DEMs and have been investigating how to process them into something useful. Does anyone know how, or even if it is possible to read coordinates and elevation data from ...
11
votes
3answers
1k views

Detrending DEMs? - Removing the elevation trend over sloped surfaces (diagram included)

Is there a known methodology for removing the trend from a DEM surface? For example, if I had a DEM of a river, that river would flow from high elevation (upstream) to lower elevations (downstream). ...
4
votes
1answer
577 views

Is it possible to reverse the trend/values of a raster?

For example - if I have a raster DEM covering a stream with higher elevations in the west (up river) and lower elevations in the east (down river) is it possible to reverse this trend so that the east ...
8
votes
5answers
657 views

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 ...
7
votes
1answer
9k views

creating a dem from contours

I have a large set of contours that I received broken down into several different subsets. I have merged most of the subsets together creating a larger set of contours in three different files. I have ...
8
votes
4answers
2k views

How to aquire a topographical map of Britain?

First of all, let me say that I know next to nothing about GISs. I'm trying to find / make / aquire a topographical map of britain. I want to use it as a height map in Dwarf Fortress so it needs to ...
5
votes
1answer
328 views

When merging two DEMs, do they have to be in the same pixel bits?

I have a simple question. I have 2 different Digital Elevation Modeling (DEM). One is the state DEM and has 30m and has 16 pixel bit. I have a couple of smaller DEM that has 30m but they have 32 pixel ...
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2answers
1k views

DEM problem in ArcGIS

I have a 32 bit DEM with resolution 0.5 * 0.5 and range of elevation is 1299 to 1489. When I want to export or use copy raster tool or create fill in Arcgis, the results are elevation between ...
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1answer
443 views

Importing ERDAS-processed GTOP030 dem data into ARCGIS

I have two GTOP030 DEM images. After downloading them, I have imported into ERDAS and mosaiced them. Then I have exported it to .tif file in order to open it in ARCGIS. But when I tried to open it in ...
3
votes
1answer
687 views

Solar radiation calculation from GTOP030 DEM image

Can you help me to calculate solar radiation from GTOPO30 DEM image at the 30 m spatial resolution. I'm trying to do this many times using spatial analysis solar radiation calculation tool in ArcGIS. ...