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

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4
votes
1answer
913 views

How to give elevation information to a polygon feature class using existing TIN file ? (geological mapping)

I'm an ArcGIS 10.1 user. My issue: I have a printed form of a map which depicts geological bodies being surface rock occurence. Additionaly, there are elevation contour lines. I digitized the map by ...
1
vote
0answers
287 views

What steps does SAGA GIS take when calculating Topographic Wetness, specifically when handling depression filled (by ArcMap) DEM

I am a grad student involved with hydrological modeling. In the model I work on, we are calculating the Topographic Index (TI; without transmissivity - or set to 1) using Quinn's MFD algorithm. We do ...
3
votes
1answer
176 views

Elevation maps from point clouds: TPS vs. what other methods

In the reply to another question, @thehealingprocess refers to "...a comparison of interpolation methods for interpolating elevation maps from LiDAR clouds, and in almost all scenarios thin ...
5
votes
1answer
758 views

When computing flow direction, the D8 algorithm is used - are there major differences if others are used?

I am a student working with Hydrological models. Within these models we can route water across a DEM (within a delineated watershed or just within an un-delineated DEM) using many different flow ...
1
vote
1answer
961 views

QGIS DEM (Terrain models) Mode Slope creates wrong data [duplicate]

I have a DEM raster file downloaded from the USGS site. The file can be downloaded here. I am trying to create a slope raster in percent with the DEM tool in QGIS. The GDAL command is the following: ...
3
votes
2answers
835 views

How to create 3D water depth with ArcScene?

I was trying to visualize flood depth in 3D using ArcScene. What I had for this purposes are: high-resolution DTM of the valley orthophoto and Raster with flood depth information. I have draped ...
1
vote
1answer
2k views

Fill sinks error in arcHydro

I am working on a project that is modeling runoff at a county level. The DEM used is lidar derived and has a 5 ft resolution. The general workflow I am flowing is Sink evaluation Sink Selection (to ...
1
vote
3answers
331 views

Calculate Number Of Pixels Visible From Pixel

I am looking for a way in which to take an input DEM and create an output raster whose pixel's value is the count of pixels "visible" from that location. I use ArcGIS with Spatial Analyst, but also ...
2
votes
2answers
118 views

What are the ways we can control the quality of a DTM?

I imagine that for DTM obtained from Stereoscopic procedures or interpolation from a set of topographic points a comparaison with the original data can help, but what for DTM obtained from Remote ...
1
vote
1answer
815 views

Where can I obtain 3D data for Singapore?

I am looking for providers of 3D maps/models of Singapore. This might be either from photogrammetry/laser techniques or based on a DEM + building footprints/landuse with a height attribute. Is any ...
2
votes
0answers
71 views

Define uphill side of roads and buildings

I have a big raster of a mountain region and I need to extract the uphill side of roads and buildings, from these elements to the pick of mountains. For a road I know the uphill side changes in ...
0
votes
1answer
250 views

How determine data type of points in geotiff DTM?

I have some DTMs in geotiff files. I need to read them in C# and I've decided to use libtiff for that purpose. After some investigations, I've found that there are tiled tiffs, so I use ReadTile ...
1
vote
1answer
289 views

How to use ArcMap for HydroPower Potential

I am trying to determine the sites for small hydropower. I have a elevation dem, rainfall data, Curve number data (from soil and landuse shapefiles). I have already used the DEM to fill sinks, find ...
3
votes
2answers
436 views

Merging DEMs of different grid size

I'm trying to merge two grids with different cell size. One has a cell size of 10m and the other 50m. The 10m one covers a subarea of the 50m one. I know that the most accurate one is the 10m one and ...
0
votes
1answer
94 views

DEM difference looks like a hillshade

I wanted to find the elevation difference between 2 DEMs. When I got the data, I had to georef one image and had to aggregated it too because their cell values do not match. I also tried to resample ...
3
votes
3answers
2k views

Creating DSM and DTM from a LAS using a freeware solution

Is it possible to export a surface and terrain model files from an aerial, LiDAR point cloud (LAS) set? I am using SAGA GIS for very basic operations, but I couldn't find this option (and I have a ...
0
votes
0answers
103 views

r.shaded.relief plugin on a DEM layer

I loaded a raster digital elevation map from the DEM explorer website. I defined the projection and created a mapset. I then loaded the raster file into GRASS with the r.in.gdal plugin to create a DEM ...
0
votes
0answers
17 views

Adding a Z Unit [duplicate]

I'm struggling with the Z Unit conversion of some data. Both the NHD data and my DEM are in a GCS with Decimal Degrees. These data sets project perfectly on the fly, but after I adjust the Z Unit of ...
1
vote
1answer
455 views

Adjusting Z Units on a DEM

I am learning how to use ArcHydro and attempting to change the Z Units because I get a warning message saying the Spatial Reference Doesn't Match. The DEM was in Meters, and I adjusted the Z Unit to ...
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 ...
3
votes
2answers
1k views

Create Contours From a DEM without 3D or Spatial Analyst

I'm wondering if there is a way to create contours from a DEM using ArcGIS without 3D or Spatial Analyst Extensions. I know that there are a few questions out there pertaining to this (How to create ...
3
votes
2answers
3k views

How to produce a CSV file from .tif file with elevation data? [duplicate]

just want to ask, I have a .tif file that contains all the elevation of a country. How can I convert that to a CSV file that contains x,y,z values where x and y are the latitude longitude respectively ...
7
votes
2answers
3k views

how do you identify ridges on an elevation raster?

I was wondering whether anyone might be able to tell me in layman's terms how to extract or differentiate between ridges and hilltops from 10m elevation data using ArcGIS 10.1?
2
votes
2answers
411 views

Terrain Accessibility map using GIS (ArcGIS or QGIS)

I need to make an accessibility map showing the walking distance based on the terrain and availability of road networks, could anyone point me in the right direction where i could learn to do so. ...
6
votes
4answers
742 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 ...
1
vote
2answers
780 views

DEM/Raster Peak and Valley identification and/or elimination (non-generalization)

I am an curious is there is a tool or process that can identify and/or eliminate obvious peaks and valleys in a DEM. I have looked into smoothing but I am interested in keeping the original sharpness ...
8
votes
2answers
3k views

DEM Elevation Units

I'm fairly new to the GIS world, and have a quick question. I'm currently using 10.1. I do not know much about rasters, so does transforming a DEM from one projection to another automatically convert ...
12
votes
1answer
10k views

When to use IDW vs Kriging Interpolation for DEM creation?

I'm trying to create a DEM using point data spaced very regularly about 10m apart. The area I am interpolating is an educational facility with many flat parking lots and football fields but still has ...
0
votes
0answers
300 views

Estimating sunlight hours from slope, aspect, and latitude

I'd like to estimate annual sun hours (or insolation, or solar radiation) for 4 points, 1 each on the four sides of the summit of a hypothetical flat-sided mountain. I have slope and aspect for each ...
1
vote
1answer
2k views

Creating Cost Surface Raster for Least Cost Path Analysis?

I have a DEM raster and would like to carry out a cost path analysis. Among other factors such as slope, proximity rivers etc. I would also like to take elevation into consideration. According to ...
0
votes
1answer
76 views

generate subcatchment starting from a DTM [duplicate]

I would like to know if there is a plug-in in Quantum GIS, which can help me to generate subcatchments starting from a DTM. Thank you very much!!!
3
votes
1answer
577 views

Create DEM from cartosat stereo pairs?

I have two carstosat stereo pair images. All i need to do is to extract DEM from those. So, i tried it doing with OSGeo4W. but i didn't succeeded in it. So IS there any other softwares or opensource ...
4
votes
2answers
2k views

Drawing irregularly shaped boundary polygon around set of LAS points using ArcMap?

I am working with a set of LAS data which is irregularly shaped, picture a starfish as the point coverage, surrounding the starfish may be water on one side, may be more land elsewhere but no points ...
2
votes
1answer
217 views

NASA ASTER DTM - what is its datum? What are the elevations relative to?

I have downloaded some data from http://asterweb.jpl.nasa.gov/gdem.asp I would like to relate the elevations to some coastal data which is estimated to a specific ordnance dataum. Can anyone tell ...
8
votes
3answers
2k views

How to get the subbasin area of each specified river segment?

I have a DEM file of one district, and I have used those following tools in spatial analyst tools in ArcGIS 10.1 to get files related to the original DEM file: Fill Flow direction Flow accumulation ...
0
votes
0answers
46 views

qgis - slope from DEM - errors due to projection and oversimplified 'z factor' [duplicate]

I'm trying to generate a slope raster from a DEM raster. It seems there is a pretty significant error due to the 'z-factor' option. I'm fairly new to this, but some other posts and responses ...
0
votes
0answers
75 views

determine the catchment area from dem or hillshade [duplicate]

I want to determine the catchment area of river from hillside. Is there a plugin that I can use in qgis ?
1
vote
1answer
155 views

How to: script convertion from SRTM to 3D printable file?

Given a STRM3.tiff file as input. How to convert this STRM.tiff file into a 3D printable file ? which I may load into most 3D printers' sofwares. My objective is to print some terran, lunar, or ...
0
votes
1answer
90 views

Change slopes derived from DEM

I have a DEM for a region over which I want to simulate an ecological process. I would like to run several simulations for the same region but I want to alter the topography for the simulations. ...
1
vote
1answer
1k views

Creating Random Points in ArcGIS 10.1

I would like to create random points across my study area (which is a DEM raster) using the Feature Class> Create Random Points. However, I need to select/copy/move/delete these points and re-arrange ...
0
votes
2answers
137 views

Two r.mapcalc calculations return a much bigger raster cell size than the input raster

I tried the following calculations with a GeoTiff sample, having a cell size of 25m: Calculating the togographic exposure (TOPEX) and estimating the mean topographic curvature Both, the resulting ...
2
votes
0answers
194 views

Whats the best way to create bathymetric contour lines?

I have a raster dataset with both Topographic and Bathymetric stored in it. What is the best way to create exact contours of the lake-bed? This becomes tricky when I want to make the contour for depth ...
0
votes
1answer
548 views

Where to obtain LiDAR Data for Romania?

I need LIDAR Data for realizing a urban hydrology study (Romania areas), whence I can get this data? There is a chance to obtain data for this area (Cluj-Napoca city)? I'm PhD student are chances to ...
1
vote
2answers
512 views

How to identify valleys on DEM in ArcGIS 10.1 [closed]

First, What is the best and easiest way to identify valleys in a DEM raster? Second, how do you create a least-cost pathway for each valley in a region based on low angle slope and proximity to ...
3
votes
2answers
3k views

Cropping Geotiff with gdalwarp

I downloaded a geotiff from the recently published 25m-DEM of the European Union (see: http://courses.neteler.org/eu-dem-new-digital-surface-model-at-25m/). One tile has about 5GB so I would like to ...
2
votes
1answer
470 views

qgis2 slope analysis from NED data gives crazy histogram

I'm attempting a simple slope analysis in QGIS2 using the plugin at Raster -> Terrain Analysis -> Slope. The slope output layer has a very strange histogram, basically spikes at 0 and at 89.9098 with ...
3
votes
3answers
1k views

How to calculate peaks in a DEM

How could I extract all peaks from a DEM (large mountainous area)? Peak means something like: a pixel which is sourrounded by other pixels with smaler elevation numbers in a area arround the "peak-...
6
votes
2answers
186 views

How to automate creation of toe of slope from DEM?

I was looking for an automated process to "identify" the toe of a slope from a DEM and ran across this ESRI thread and technique: I am at Step 7 but have no idea how this is accomplished. I get it is ...
0
votes
1answer
261 views

calculate least cost pathways for a region and create distance rasters to rivers [duplicate]

How do you calculate all the least cost pathways that exists for a region? I would like the output map to display all routes (and was wondering whether this can be done in one set of operations). I ...