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

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6
votes
2answers
4k 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 ...
1
vote
1answer
231 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 ...
4
votes
4answers
710 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 ...
1
vote
1answer
483 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) ...
2
votes
1answer
911 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 ...
1
vote
2answers
394 views

How do I intersect DEM and a polyline?

I'm working on Qgis, I need the longitudinal section of a river. Thanks
1
vote
1answer
520 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 ...
2
votes
2answers
215 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 ...
3
votes
1answer
164 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 ...
1
vote
1answer
438 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 ...
2
votes
1answer
88 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!
5
votes
2answers
2k 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
votes
1answer
453 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 ...
5
votes
4answers
815 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 ...
2
votes
1answer
49 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 ...
1
vote
1answer
172 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 ...
4
votes
5answers
3k views

Problems merging DEMs or other raster datasets? Clipping Raster dataset to vector line?

I have two DEMs that I am going create a hillshade from, and ultimately want one hillshade clipped to a county boundary. I am running into a couple problems, though. When I try to merge the two ...
2
votes
1answer
287 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 ...
7
votes
3answers
836 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 ...
3
votes
1answer
558 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 ...
1
vote
1answer
97 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 ...
5
votes
2answers
371 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 ...
5
votes
1answer
4k views

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 ...
11
votes
1answer
540 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 ...
0
votes
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 ...
3
votes
1answer
712 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 ...
4
votes
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....
2
votes
2answers
918 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 ...
6
votes
3answers
1k 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 ...
1
vote
1answer
244 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 ...
8
votes
2answers
865 views

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 ...
1
vote
1answer
829 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 ...
2
votes
0answers
495 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 ...
2
votes
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) ...
0
votes
0answers
210 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 ...
1
vote
2answers
942 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
votes
1answer
524 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 ...
6
votes
1answer
359 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 ...
2
votes
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 ...
5
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 ...
2
votes
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] ...
3
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 ...
4
votes
1answer
670 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 ...
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). ...
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 ...
5
votes
1answer
366 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 ...
1
vote
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 ...
2
votes
1answer
589 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 ...
8
votes
5answers
687 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
votes
1answer
608 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 ...