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

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2
votes
1answer
62 views

Extracting area from DEM Raster?

After applying constraints to the DEM I polygonised the raster (using GRASS r.to.vect.area) The result is shown below with a lot of vector with resolution = [30 * 30] Is there any solution to make ...
0
votes
2answers
60 views

Equidistance on line contour from DEM

I am using a SRTM 30 meters for slope and elevation. When i'm using this 30x30 rasters to generate contours i set a 30m equidistance for contour, and the results are ok. Now i'm wondering if it's ...
4
votes
2answers
695 views

Stitching Bathymetry and DEM data together in ArcMap?

I have a DEM built from Lidar data and bathymetry survey points for a river which flows on the DEM surface. My understanding is that Lidar data is not able to capture bathymetry under the river flow....
3
votes
1answer
407 views

SAGA tool 'Relative Heights and Slope Positions' - What do results tell me?

I am currently trying to get in morphometry, using the SRTM 30m DEM. I was recommended to test the SAGA mudule 'Relative Heights and Slope Positions' (http://www.saga-gis.org/saga_module_doc/2.1.3/...
4
votes
1answer
133 views

Raster cells with no data being generated by las2dem?

Anyone has an idea where these lines (with no elevation data) come from? They are generated while using the las2dem tool from LAStools. What needs to be done to avoid this? The raw data (.las file) ...
0
votes
2answers
68 views

Update raster pixels on a DEM

I have a DEM in the form of a raster that I would like to update in certain locations. Ideally, I'd like to be able to create a separate polygon or point shapefile with the values, in the correct ...
1
vote
1answer
19 views

In QGIS, add to existing dem tiles and expand corresponding contour coverage within a project

In my first QGIS project I have dozens of digitized layers that have spread beyond the contour and dem tile area that I started with. Please recommend how to safely expand or replace the dem and ...
0
votes
2answers
1k views

Create DEM with 1 foot contours from lidar data with 1.4 meter resolution

I have Lidar data which contains multiple .las files for an entire quad. I have figured out which .las is the area I am looking for. I was told the data is in 1.4 meter resolution and would work to ...
2
votes
0answers
29 views

Combining multiple DEMs into one file geodatabase

I have multiple file geodatabases (approximately 240) each contain a DEM. My issue is taking the DEM from each and putting it into a single file geodatabase without alot of mind numbing work. ...
1
vote
0answers
48 views

Quantifying amount of sunlight falling in a region

I am trying to objectively quantify or provide some form of indication that could point toward the amount of sunlight Anyone knows if there are any datasets (either instrumental or remotely sensed ...
3
votes
1answer
70 views

Simplify / generalization of flow lines

I'm trying to make a model of surface runoff of rain water. I'm using GRASS GIS function r.flow, which generates nice smooth lines of runoff. What I need is edit these flowlines someway to avoid ...
0
votes
0answers
71 views

how to define threshold value in r.stream.extract

I want to generate streams using r.stream.extract. on what basis we have to define the threshold value. I am using aster dem with 30m posting.Also i want to know the minimum stream length to be ...
6
votes
4answers
747 views

What are the most efficient Geographic Weighted Regression packages?

What are the most memory efficient open source packages for calculating a geographically weighted regression (GWR)? I am in a situation where I need to do a geographically weighted regression on a ...
6
votes
1answer
444 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 ...
10
votes
3answers
3k views

Create DEM from stereo pairs using ArcGIS for Desktop or Open Source GIS?

Does ArcGIS Desktop or any of its native extensions allow me to create DEMs from stereo pairs (acquired by satellite, GeoEye 1)? If the answer is a clear no, brownie points will go to an answer that ...
0
votes
0answers
17 views

Extracting Elevation (DEM) from air photos using open source software? [duplicate]

I have a few pairs of stereo air photos and I want to extract a DEM from them. I think that is possible using PCI (OrthoEngine), but I would like to do it using Open Source (or at least free) ...
2
votes
0answers
148 views

High Resolution Terrain Data for the Philippines

Where can i download Philippines terrain data that is better than the 30 m ASTER global dataset?
1
vote
2answers
133 views

Topographical Elevations for Central Africa and Cameroon

I am using QGIS and I have been faced with the problem of topographical maps. From searching online I could only find data for the United States. Google maps offers elevation contours, however I am ...
2
votes
2answers
455 views

How to extract elevation values at line start and end points from a DEM?

I am new to the whole gis-experience and need your help working with QGIS. I have: DEM raster with heights (3d) line-shapefile which contains the rivers (2d) I need: heights for "start" and "end" ...
2
votes
1answer
2k views

Problem merging two rasters in Qgis

I have two rasters in Geotiff, same CRS. I tried to merge them and I have this error code ERROR 4: `C:/Anita_Tepoztln/Rasters/e142.tif' does not exist in the file system, and is not recognised as a ...
1
vote
0answers
41 views

Z factor to get the results in square meters and cubic meters?

I have a DEM surface in WGS 1984.I want to calculate surface area and volume in different elevations.I wonder for example If I want to measure the area and volume below some height how shall I set the ...
1
vote
2answers
415 views

Masking out places with elevation below 5 m from a DEM

I have a DEM of a study region; I want to modify the DEM in order to reflect the coastline outlook when the sea level was 5 meters higher than today. What I have done so far is to use 'Raster ...
0
votes
1answer
71 views

Determining length of roads that fall under low elevation using ArcGIS Desktop?

I am working on a project on sea level rise impacts of roads. Basically I need to determine length of roads that fall under low elevation (from 1m to 5 m elevation). I have a DEM file and road shape ...
2
votes
1answer
119 views

Calculating slope for points with downhill slopes rendered as negatives in ArcGIS

I have a DEM and a series of points. I'd like to measure the change in slope along the series of points. Distinguishing between uphill and downhill slopes matter to me, and ArcGIS' slope function ...
2
votes
1answer
905 views

How to know if flow accumulation map reflects true catchment areas?

I have calculated flow accumulation (img file) using this DEM (img file), which is 0.5 degree resolution, using arcmap. I am wondering if the cell accumulation value can directly be translated into ...
1
vote
0answers
27 views

line from min to max of a digital elevation model

I have some geometries as multipolygons and a dem (digital elevation model). I need a line from the max value to the lowest value of the dem for every multipolygon. Is qgis a tool i could use or do i ...
9
votes
7answers
12k views

Open source tool to convert a DEM to a 3D model

I would like to convert a DEM (Digitial Elevation Model) file (e.g. from SRTM) into a 3D model that I can then edit with regular 3D modeling tools (e.g. Meshlab/Blender/etc.). However I'm using Ubuntu ...
0
votes
1answer
360 views

How to extract points from a Digital Elevation Model in ArcGIS 10.1?

More specifically my question would be if there is a way to create a grid over the digital elevation model in GIS and extract points, or elevational data, from the intersecting points of the grid? I ...
1
vote
0answers
85 views

Calculating slope from elevation returns hole when using ST_Slope in PostGIS

I have rasters from the National Elevation Dataset loaded into a PostGRES database and am using the built-in function ST_Slope to calculate the slope. However these contain many holes where there is ...
0
votes
0answers
375 views

Processing LAS dataset in QGIS 2.8.2 [duplicate]

I need to extract DEM from LIDAR dataset in QGIS 2.8.2. I have installed LAS tools in QGIS. I cannot configure my LAStools because I do not get Processing-->Options and Configuration and instead I get ...
1
vote
1answer
211 views

Is it better to take the elevation of a GPS unit or that of a Digital Elevation Model?

When searching of gps routes in wikiloc, for the trailrunning race "Transvulcania" I have several routes to look. I downloaded a lot, but every route has a distance between 71 kilometers and 74 ...
13
votes
5answers
933 views

Dikes extraction from DEM

I do have DEM of 1x1 meter and original LiDAR point cloud in .las, that DEM is made of. I need to extract river dikes (highest points of the dikes) to vector feature (point, polyline). Any idea for ...
0
votes
1answer
83 views

ArcGIS Raster To Multipoint Mac/OSX alternative

Is there an alternative to the ArcGIS Raster To Multipoint tool for Macs? The VIP thinning method is particularly of use. A comparative point cloud thinning/simplification tool to this would just as ...
4
votes
1answer
314 views

How to extract most probable flow line from multiple lines?

I have to apply uncertainty principle to computing flow accumulation using Monte Carlo method. I generate raster with random numbers which represents mistakes in creating DEM. Then I apply those ...
1
vote
1answer
233 views

Getting aspect and reclassifying raster files using Python in a loop

By using Python in PythonWin 2.7.3, I tried to obtain aspect files of a list of raster files in a folder(called database_Dem20) and save it to another folder, database_Dem20/testOutput. In the same ...
1
vote
0answers
76 views

How to interpolate a Raster DTM

I have a GeoTIFF DTM produced from Agisoft Photoscan at 0.05 m resolution. However the interpolation used by the program to remove the riparian vegetation has used points from the channel, thus ...
0
votes
2answers
546 views

Reversing Extract by Mask in ArcGIS for Desktop? [duplicate]

I have a DEM and I want to apply some tools to it (fill and others). In my DEM I've zones (drawn as mask) that need to be exlcluded from that processing. I don't want to apply the processing to the ...
9
votes
2answers
1k 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
112 views

Merging USGS DEM files in ArcMap?

I'm trying to merge my DEM files into 2 separate files, one will have 4 files and the other will have 3. I've been reading every post from when someone asked this before for over an hour and I'm still ...
4
votes
2answers
503 views

Interpolate Temperature Using DEM

I want to "co-interpolate" temperature with DEM. I have SRTM 90m aggregated to 1km and I want to "co-interpolate" my DEM with points with temperature data. How do I do this? I am using ArcGIS 10.
0
votes
2answers
109 views

QGIS - Edit Surface DEM to Add Buildings

Okay, let me start by saying I'm no expert in QGIS, I'm more into engineering. I'm building a 2D hydraulic model and I would like to add the building footprints (elevated) to my DEM, so flow will go ...
4
votes
2answers
371 views

DEM local adjustments - terraforming

I'm looking for software that can perform local adjustments in DEMs with tools similar to paintbrushes used in graphics editing programs but streamlined to respect geomorphology. To give you an idea ...
0
votes
1answer
108 views

Understanding InSAR interferometry?

I understand that the result of InSAR interferometry yields a LoS deformation and if deformation in the vertical or horizontal is to be computed, it should require additional gps observations at the ...
1
vote
0answers
38 views

Merging DEM files using PostGIS

I have several DEM files and I want to merge them to create a mosaic. I found the St_Union(raster) or St_MemUnion(raster) functions but I don't know how to use them. Are there any other solutions?
8
votes
3answers
613 views

Handling mountain shadows when classifying Landsat 8

I'm trying to classify some area in northern Mongolia using Landsat 8 satellite images from 2013. Since the recordings were made in winter, the sun is very low at the acquisition time. Therefore there ...
0
votes
5answers
435 views

How to create 10m DEM from 30m DEM?

I am not regularly working in raster analysis. I have a 30M DEM and I would like to create a 10 DEM out of that. Is it possible to do this using QGIS? and How? EDIT: (I understand that a sub ...
1
vote
0answers
26 views

Export of a Raster Not Preserving Color [duplicate]

I'm trying to make a pretty shaded relief map using the technique described here. I've done this process several times in the past without any problems but today am perplexed about what is going on. ...
1
vote
1answer
163 views

How to find the coordinates of the lowest point in a polygon

I am working in QGIS 2.6. I have a file of several polygons and I want for each one, to find the lowest point (where is it located and its elevation). I am using "Grid statistics for polygons" which ...
2
votes
2answers
241 views

Does a SRTM DEM image show details such as fields?

I'm working through the QGIS Training Manual where I have a step to get ... ... raster images (SRTM DEM) which cover the region you have selected for your course. SRTM DEM can be ...
2
votes
2answers
242 views

Creating basic DEM file with flat geometry in ArcGIS Desktop?

I want to create a basic DEM file in .ascii format which will just be a rectangular grid and with no slope i.e same elevation at every cell. Please provide information on how to achieve this. I am ...