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

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792 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 ...
8
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2answers
7k views

Is there a way to clip a raster using a vector polygon without having Spatial Analyst?

I have ArcView 10 and I'm trying to clip a DEM (TIFF) to a wilderness boundary (polygon). I know ArcView won't let me do this without Spatial Analyst, but I don't have $2500. I tried exporting my ...
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1answer
269 views

arcgis python window VS pywin32

I have problems while using the ZonalHistogram function in Python. It seems to give strange results, while, with the same code run in arcgis' python window everything works fine. I am trying to study ...
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4answers
1k views

Is there a way to programatically force RGB (3 bands) in a raster with arcpy?

I'd like to include conversion to a 3 band RGB raster in a script to prepare multiple DEMs for image processing. The input files are rasters extracted from a raster mosaic. The manual option is to ...
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1answer
780 views

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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1answer
1k views

Extraction of DEM from netCDF file into ASCII XYZ format

I need to extract a DEM of a waterbody from a netCDF file so I can ultimately convert the DEM into xyz format. I'm not sure how to go about doing this, and so far, I have tried to create raster layers ...
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2answers
540 views

How do I intersect DEM and a polyline?

I'm working on Qgis, I need the longitudinal section of a river. Thanks
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1answer
739 views

Using Latitude and Longitude with SRTM3 DEM file

I am new to working with DEM files but have a need to be able to work with SRTM3 DEM files to calculate elevation given a Lat,lon coordinates. I understand from reading the documentation that the ...
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2answers
223 views

Issue converting DEM in ASCII with LO17 (apparent) projection

I'm a newbie where GIS is concerned, so please don't hesitate to point me to a manual. We've got DEM files without any projection information. One is called 000426_LO17_200M_BD16_25.ORT and contains ...
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1answer
191 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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1answer
594 views

How to calculate an hypsographic curve of a raster trhough a DEM

I am using Arcgis 10.1. I have a MODIS raster from the NSIDC website with a pixel resolution of 500 m and an attribute table with the fields 'VALUE' (as the code of snow, clouds, etc.) and 'COUNT' (as ...
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1answer
93 views

Looking for literature on correcting one DEM with another

I am looking for some scientific papers (any language) according how to deal with the correction of one DEM with a other (such as ASTER with SRTM). Any idea? Thanks!
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2answers
3k views

How to compare two DEMs and show their difference?

I want to compare my DEMs (ASTER GDEM2 and SRTM4.1). I know, that the GDEM has some extreme "holes" with totaly wrong elevations (I found 3 of them in my working area). Now I need to know, if there ...
2
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1answer
497 views

How to manage null values in QGIS

I made a merge of several AsterGdem blocks near Egypt and Israel. I have portions of the Dead and Mediterranean Seas. Since near Galilea elevations are below sea level this makes the following problem ...
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4answers
1k views

Does a value in srtm dem file refer to the center or corner of a cell?

I'm working with srtm dem files. They are ascii text files containing a table/grid of elevation values. At the top of the file is some metadata to locate the grid in lat/lon: xllcorner ...
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1answer
55 views

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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1answer
187 views

srtm30 image: some are grayscale some are black & white

I downloaded these DEM files, http://www.dgadv.com/srtm30/ srtm30 globe. I open the DEM files in Multispec. Some of them are black& white, some are automatically grayscale. How do i get them ...
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1answer
336 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 ...
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3answers
1k views

Creating raster or vector raster from DEM point file?

i have a point shape of 75.000 elevation points in a regular 5 m grid. We now want to create a polygon grid with the elevation points as "centroids". Unfortunately, all attempts to do so fail: I ...
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1answer
656 views

Correct ASTER with SRTM or Topographic Map

I have a problem with my DEM again. I decided to use ASTER GDEM2 (for different reasons). ASTER GDEM2 have its problems, I know, and I dont want to discuss that again. I have to use it, because SRTM ...
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1answer
108 views

How do I retrieve an arc ascii grid file from NED 1/3 second data using python and OWSLib

I have my bounds, and have been able to connect to the server http://imselev.cr.usgs.gov:80/wmsconnector/com.esri.wms.Esrimap/USGS_EDC_Elev_NED_3? in python. What I don't know how to do is send a ...
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2answers
425 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 ...
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1answer
656 views

QGis raster terrain analysis - The curvature filter puzzles me

I am a french Master student at university Grenoble INP, and during my master project I have worked on DEM (raster) terrain analysis. Thus, I have read the source code of several QGis-1.7.4 raster ...
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1answer
4k 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 ...
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1answer
961 views

Export SRTM30 Dem file as 3d

i have downloaded some SRTM Dem files here: http://dds.cr.usgs.gov/srtm/version2_1/SRTM30//srtm30 They are from the USGS site. I would like to export them as 3d. I have ran through a few ...
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1answer
2k views

How to create a Digital Elevation Model

How to create a DEM starting from layers shapefile "contour lines" and "shares"? which module of GRASS I need to use? thanks for yours responses....
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2answers
1k views

SAGA GIS: How to load an .hgt file?

I want to display and work with the data from http://dds.cr.usgs.gov/srtm/version1/Eurasia/ in SAGA-GIS but am having difficulties knowing which module I should use to load the data. As far as I know ...
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3answers
2k views

What is a good way to produce wire frame images from DEM?

As part of a project for a wind turbine assessment, I would like to make a wire frame image to compliment my Viewshed / line of sight and Photo montage. I have never created a wire frame image from ...
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1answer
267 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 ...
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1answer
1k 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 ...
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2answers
131 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) ...
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253 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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2answers
1k 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, ...
4
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1answer
644 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 ...
4
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3answers
4k 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 ...
6
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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 ...
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2answers
3k 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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4answers
5k 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 ...
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1answer
1k 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 ...
13
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3answers
2k 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). ...
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1answer
397 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
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1answer
767 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 ...
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5answers
882 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 ...
4
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2answers
1k views

Translating grid to USGS .dem in C# via GDAL

I am attempting to translate ArcInfo binary grids to USGS DEM format (.dem). I have installed the GDAL .NET bindings thru this build installer. I can get to GDAL in my C# add-in I am working on. ...
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1answer
434 views

Command r.sunmask in GRASS

I have hypsometric model of relief, and I need to visualize shadows. I was suggested to use GRASS command r.sunmask, so I tried to set time values and run command, but it gives me an error "ERROR: ...
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2answers
724 views

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 ...
6
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2answers
868 views

What's a good toolchain to reproject some PNGs in plate carre to UTM?

I have some PNGs produced from Canadian DEM data. They're 1201px by 1201px heightmaps. Each one represents one quarter of a degree latitude and one quarter of a degree longitude. But I want to work ...
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3answers
1k views

getting from a DEM to points that could be used for a TIN

I have a DEM, and would like to create a set of points that I can use to make a mesh for a 3d modeling program, such as Maya, Blender, or SketchUp. If I were to make a TIN from a DEM in ArcGIS, ArcGIS ...
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1answer
457 views

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 ...
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1answer
6k views

Watershed Delineation

I am trying to delineate just the catchment area of some lakes, and am wondering the correct way to do this. I already have a filled DEM, along with a flow direction and a flow accumulation raster. Is ...