For questions about Digital Elevation Models (DEM), Digital Terrain Models (DTM) and Digital Surface Models (DSM)

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2
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2answers
93 views

Finding DEM/HIllshade sources California

Creating watershed maps for schools. I want to color ramp the elevation to show low and high points. What kind of files do I need and where to find them?
6
votes
1answer
600 views

Interactively determining upslope and downslope areas on DEM?

I know SAGA GIS can be used to interactively generate maps of upslope and downslope areas for a cell within a DEM, but the output is pretty ugly. An upslope area is defined as all cells (for a ...
2
votes
1answer
797 views

Extract elevation data from Landsat / MODIS imagery?

Just curious, have anyone tried to extract elevation data from LANDSAT or MODIS imagery? So far, I came across one journal by Toutin who did so using adjacent LANDSAT 7 imageries. Results seem pretty ...
2
votes
2answers
270 views

How can you create a depth raster from a DTM and a polygon in QGIS?

I have a DTM raster and a flood outline in polygon format - how do I create a depth raster for the flood outline (i.e. flood level minus DTM level)?
-1
votes
1answer
511 views

Automatic Lineament Extraction from satellite images using ENVI? [closed]

Can you tell me the steps of automatic lineament extraction from satellite images? Can ENVI perform edge detection and the lineament extraction?
0
votes
0answers
202 views

Striping Artifact in Aster DEM Mosaic

I'm working with SRTM and ASTER data for a university project. My goal is to delineate watersheds and evaluation of these with ArcGis 10 and ArcHydro. But a striping error occurs with the flow ...
3
votes
1answer
132 views

Grid-like artifact visible in contour layers?

I am creating contours from an Aster DEM in ArcMap 10.1 I see a grid pattern appearing, particularly in areas of dense contours: I see the same artifact if I create a Hillshade layer so presumably ...
1
vote
0answers
44 views

How to extract elevation data from ASTER/SRTM? [duplicate]

I just want to know if there are any other tools available in QGIS apart from the Point Sampling tool to extract elevation data from ASTER/SRTM/CartoDEM (for India) data? When I convert these images ...
2
votes
1answer
842 views

Converting LAS file to .asc DSM? [duplicate]

I want to count trees in SAGA GIS and I am trying to follow the steps described in Counting trees using segmentation and vectorization in SAGA Gis from dominoc925.blogspot.com (05th, March, 2012). ...
0
votes
2answers
143 views

TIN to Raster - specify raster's origin

How could I specify raster's origin, while using arcpy.TinRaster_3d?
0
votes
1answer
32 views

Is it possible to reveal the relief parameters “slope inclination” and “slope exposure” by dint of ASTER GDEM?

I’m trying to find information in technical and scientific articles – is it possible to reveal the relief parameters “slope inclination” and “slope exposure” by dint of ASTER GDEM? Or we can define ...
8
votes
2answers
179 views

What is a good metric for mapping accuracy

I have recently received a dataset that supposedly mapped the altitude a given region (a DEM). I would like to determine the accuracy of the new map by comparing it with a previously generated DEM. ...
2
votes
1answer
258 views

Rasterizing Contours - How to remove 0 values

I want to convert vector contours to a DEM. From other posts, I wanted to utilise the Grass r.surf.contours tool. Initially I converted the vector contour layer to a rasterized contours using the "...
3
votes
1answer
55 views

Algorithm behind custom tool of ArcGIS for Desktop called xyz2grid21?

I am a researcher from Romania and I have used xyz2grid21 ArcGIS tool (by Min-Lang Huang) in order to convert xyz files (LIDAR data) to ASCII and ESRI grid in order to obtain a DTM. I need to know ...
3
votes
2answers
144 views

Is SRTM 3 second arc free of non-terrain features?

I made an elevation map of my study area in Macapa, Brazil. But the region has the average elevation lesser than 30 m as I can see from my map derived from SRTM 3 second arc. According to my ...
3
votes
0answers
707 views

Creating one DEM from multiple ASC files

I am struggling with this several days and now its time to ask how to do it in QGIS. I have very detailed 27 ASC grid files with overall size of 9 GB created from 1m contours of large area (600 m2). ...
4
votes
1answer
588 views

How to extract DEM (Digital Elevation Model) from 3D model

How can I extract a Digital Elevation Model from a 3D model of a building, made with SketchUp, using Blender,qgis or any other software?
5
votes
2answers
251 views

Sun azimuth on shaded relief LiDAR maps

I have a LiDAR map and want to change the view so that the ground shadow is manipulated (looking for archaeological anomalies). I think it is the sun angle that I need to alter but I don't know how. ...
2
votes
2answers
581 views

How to use OS Terrain 50 in QGIS

I am new to GIS and I wish to perform view shed analysis of wind turbines from a DEM. I have downloaded OS Terrain 50 and the data is contained within numerous zipped folders. I am using a Mac with ...
3
votes
1answer
196 views

Highest DEM pixel in polygon

I'm working with QGIS and have a big DEM raster layer with height information and a vector layer with many polygons, representing 1 x 1 degree tiles. Now I want to find for every polygon the highest ...
4
votes
1answer
760 views

Generate channel network (rainwater run off) - which algorithm is the best?

I want to compute DEM for a whole country (cca 79 000 sqr. km) and I need to be hydrologically correct as much is possible. After, for this correct DEM I need to compute drainage lines of surface ...
1
vote
0answers
201 views

Correlation between point feature (disease) and elevation

I have a problem! How can I calculate the correlation between point feature and Dem raster? Hypothesis: disease prevalence in high altitude is more than low altitude. I must do this in ArcGIS 10 and ...
7
votes
3answers
732 views

Filtering out canopies and buildings from DSM to have a bare earth elevation

Can anyone suggest methods in filtering out trees and buildings from a DSM so as to come up with a reliable DEM? What I have is a grid from a LIDAR data (.tif file, with 1m resolution). I was going ...
2
votes
1answer
399 views

How to convert ASCII in x,y,z format using gdal_grid?

I have a map saved in (AFAIK) Arc/Info ASCII format and I would like to convert it with gdal grid but I am getting errors. My data (p.csv) is in the following format: 319053.25,319301.12,544.28 ...
0
votes
0answers
111 views

QGIS DEM Output cell size does not match DEM input cell size

As my first post I offer a humble apology if this is such a basic question as to make any of you cringe. I feel like I have exhausted my search skills and read through the QGIS documentation ...
2
votes
1answer
130 views

Query DEM Elevation at Point in QGIS

I'd like to be able to pull up a DEM (or create a mosaic of them) and simply query the elevation at points I click. Is this possible using QGIS?
4
votes
1answer
153 views

In which way is height information stored in a DEM?

I'm struggling with different DEM data, because I don't know how to convert the height information in meters. When I load ASTER and SRTM tifs in QGIS, it shows me the spectrum of the grayband (0 to ...
1
vote
0answers
35 views

Converting DEM data to height information in meters using QGIS? [duplicate]

I'm relatively new with QGIS and currently I'm working with ASTER and SRTM DEMs. The goal is to create vector heightcontours with labeling in meter. Can you tell me how I can convert the grayband ...
7
votes
3answers
568 views

Is there a difference between the Planchon & Darboux and Wang and Liu depression filling algorithms? Other than speed?

Can anyone tell me, based on actual analytical experience, if there is a difference between these two depression filling algorithms, other than the speed at which they process and fill depressions (...
4
votes
1answer
482 views

Flow direction generated for river is incorrect

I am trying to generate a hydrologic model and I can not really proceed on the next processes. I have this problem on generating flow direction. I have already executed fill sinks and the next is flow ...
4
votes
2answers
870 views

What is the source of horizontal and vertical striping in USGS DEMs?

When processing 30m and 10m DEM data downloaded through the National Map Viewer from the National Elevation Dataset, we noticed horizontal and vertical striping not only in the produced results, but ...
0
votes
4answers
853 views

Using Arcpy, how can I determine min and max elevation from a raster DEM layer within my current extent?

Using Arcpy, how can I determine min and max elevation from a raster DEM layer within my current extent? I'm currently using Data Driven Pages to centre the layout on each feature extent. I need to ...
5
votes
0answers
346 views

Has anyone used ArcGIS for 'automatically' detecting lineaments from a high-resolution (1m) DEM? [closed]

I have a set of DEM's produced from LIDAR data. I am wondering if anyone is familiar with or knew of any published research papers which looked at (semi-)automatically detecting lineaments /or ...
2
votes
1answer
439 views

How to handle “illegal data type (Float64)” error when trying to convert .tif to .bil?

Each time I try to convert (in QGIS 2.2) an elevation model from .tif to .bil format a get this error: ERROR 1: Attempt to create ESRI .hdr labelled dataset with an illegal data type (Float64). ...
2
votes
1answer
995 views

Getting Negative Topographic Wetness Index (TWI) values in SAGA GIS?

I am getting negative topographic index wetness values in SAGA GIS - anyone else every get this? Not all negative values, but the minimum of the TWI range is negative for some steep watersheds we are ...
4
votes
1answer
822 views

Topographic Index - Why is upslope contributing area divided by downslope contour width and not upslope contour width?

In the Topographic Index calculation, a is the upslope contributing area per unit contour length. Is the "unit contour length" calculated from examining the contour widths of the downslope cells that ...
3
votes
1answer
225 views

Creating constant slope DEM using ArcGIS Desktop?

I wanted to create a DEM of constant slope say 1/3000. How can I proceed in ArcGIS Desktop 9.3? The area may be 1000m x 1000m or any other as per convenience.
0
votes
1answer
543 views

DXF (points and lines) in QGIS - Doesnt import z coordinates

Trying to get to grips with QGIS, coming from a Mapinfo and Civil3D background. I have a DXF file with points (X,Y,Z) and lines. I want to open this in QGIS and use the interpolate plugin to create ...
1
vote
1answer
198 views

Extracting DEM from imagery using ArcGIS for Desktop?

I'm using ArcGIS for Desktop and I'd like to know how can I extract the elevation model from a imagery of photos. I have the have each image (jpg) geo referenced. After, I don't know what tool may use ...
2
votes
1answer
471 views

Obtaining average value around polygon in raster for different cross sections?

I have elevation data in a raster, river (blue line) and the flooded area (black polygon) as shown in the image below: I want to find the water depth in the flooded area (inside the black polygon). ...
0
votes
1answer
84 views

What dem data are Flex Viewers using to create elevation profiles?

I asked a similar question a year or two ago here: Can Elevation Profile data in Arc's Flex Viewer 3.0 be exported? which appears to not have an answer. Another question regarding the Flex Viewer (3....
0
votes
1answer
69 views

Viewshed over Multiple DEM Models Possible?

I finally got the viewshed working correctly over one DEM model. However, I am wondering is it possible to do the viewshed over multiple DEMs? E.g. A Multiple County Viewshed based off one point. ...
1
vote
3answers
1k views

ArcMap - Making DEM using GPS vector data [closed]

I am new to GIS and GPS. I am going to make a digital elevation model of my school's campus using a trimble gps unit. I know the accuracy is not the best but it is just for a school project. My ...
0
votes
2answers
340 views

r.topidx error: required parameter output not set

I'm calling GRASS r.topidx from QGIS 2.2.0. I can get other tools to work on the DTM, for example r.watershed. But r.topidx I get the Oops message: Oooops! The following output layers could not be ...
5
votes
1answer
292 views

How can I get the profile graph on ArcMap to display specific points?

I currently have 2 layers: 1) DEM of existing terrain 2) Polygon in vector format of future water retention basin I need to draw cross sections across this basin for eventual cut and fill calcs. I ...
0
votes
0answers
271 views

How to create .dem file in QGIS?

I have an elevation data in .asc file, but need to convert it to .dem file to later use in COMSOL. However, in Raster--> Analyzes-->DEM I got just error message: ERROR 1: DEM Default Setup: Importing ...
2
votes
1answer
2k views

Dem file in .adf format, while .tiff is needed

I would like to use this standalone tool to get different kind of Dem visualizations (http://iaps.zrc-sazu.si/en/svf#v). I see that the program accept only .tiff DEM. Now, the DEMs I got are not in ...
1
vote
2answers
370 views

Retrieve Elevation from Color in Raster DEM

This might turn out to be a newbie question, and that would be because I'm fairly new to GIS work, but extensive online searching, asking associates with some basic GIS knowledge and hours in various ...
0
votes
1answer
680 views

Best Resampling Method for DEM reprojection in QGis

I need to reproject a DEM (aster file) in order to have the same CRS as all my other project data - I have different SHP for the same DEM's location but they have a different CRS. Which resampling ...