Questions tagged [dem]

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

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293 views

QGIS isolines from points and lines

I'm getting started with QGIS and I want to use survey data to generate isolines. Contour plugin works well except when surveyed area has linear details (say, a road) that are elevated relative to the ...
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254 views

Buffering based on topography in ArcGIS Desktop?

I need to do a buffer based on the real terrain. Like 500 meters from a polyline on all sides. I have DEM (SRTM) of the terrain. Is there a way to do that?
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85 views

Ensuring that a path goes downhill

GIS student hoping for a bit of wisdom on the Path Distance tool. I am doing a ski slope analysis, trying to find runs using cost grids (that incorporate slope, aspect, avalanche risk, etc.) While I ...
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256 views

ArcGIS create profile graph from existing point feature

I have a dataset of X,Y points (with a spacing of 20m between the points) that represents a flowline along a glacier. Next to dat, I got another point dataset of the glacier height with X,Y points and ...
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185 views

Smoothing relatively flat DEM for terrain and hydrologic analysis

I'm trying to do some terrain and hydrologic analysis from a 1/3 arcsecond DEM that I downloaded from the USGS National Map website. The issue I'm having is that the area in question is central ...
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84 views

How to extract and export “raised field” LIDAR objects?

I'm working on Windows 10. In input, I have a .LAS "GROUND_only" LIDAR point cloud (4 millions points). We're interested in geomorphological microstructures called raised field (ground elevation due ...
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72 views

Filling missing pixels of ASTER DEM

I need to perform hydrological analyses and map design purposes (hillshade creation) on a region far north. It is too northern to be covered by the SRTM DEM, therefore I am using the ASTER DEM. ...
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90 views

Why do lines appear after running Slope and/or Aspect tools? ArcMap 10.3

I am attempting to create a predictive model for my study area. I have 10m DEMs which I have merged together using the Mosaic to New Raster tool (Picture 1). I am now trying to use the Slope and ...
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78 views

Problem with contour line

I have a problem when I create a contour line from DEM, it's become sharp and not correct ( image attached ) . DEM cell size = 5m Contour interval = 5m
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361 views

How to convert raster DEM to reduce file size in QGIS? e.g. 32 to 8 bit floating point

I have a raster DTM (.tif, 32 bit floating point) which has a very large file size and is thus slowing down the software. I am looking for a way of reducing the file size without reducing grid cell ...
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89 views

Classification during DEM generation for Bare Earth Surface-ERDAS

I am using ERDAS photogammetry tools(eATE) to generate a bare earth type DEM from two Pleiades satellite images(pan-sharpened 0.5 cm resolution). I have run the process and the results were just OK. ...
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453 views

Adding Elevation Data to a Satellite Image Raster File from DEM

I have a satellite image raster file of an area and a DEM of the same area. I can Extract Values to Points by using this DEM as it contains the 'z' value i.e the elevation information in meter. The ...
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79 views

Discrepancies in SRTM 1ArcSec DEM

I have downloaded SRTM 1 ArcSec and processed it to retrieve topographic attributes. Prior to this, I have used 'fill' tool in ArcGIS as a pre processing step. Following is snapshot of clipped DEM; ...
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672 views

ArcGIS remove negative values from DEM, DEM max increases

I have a D.E.M. that has values between -1.13 and 23.33. In the Symbology, I changed the Stretch Type to Minimum-Maximum to get the true values and those previous values are what the raster draws. I ...
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637 views

How to delineate a zone of slope break

I have a DEM of a region and want to delineate about a half-mile region at the base of hills (e.g. an area where the slope changes from steep to shallow). I ran the slope analysis tool and it kinda ...
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182 views

Changing Ascii grid file inside a GeoJSON polygon

I have a Digital Terrain Model ASCII grid file that gdalinfo recognizes as AAIGrid. Its resolution is 2m. I need to alter it simulate the construction of an embankment, so as to feed it to a modelling ...
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46 views

Use of Airbus WorldDem altimetric values (EGM2008)

In France, the altimetric values are issued from a mesure of heights above the sea level based on the Marseille's tide gauge. If i didn't mess it up, the system is named NGF - IGN69 for mainland (See ...
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1k views

Display multiple ASCII (xyz) files in QGIS

I am new to QGIS and I am trying to import more than 700 xyz (it is the same as ASCII?) files into the map so I can get a digital elevation model and then get the average elevation for some small ...
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104 views

Mars MOLA .csv layer in QGIS misplaced and very small

I'm trying to add Mars MOLA .csv data on top of CTX and HiRise DEMs but when I load them all up in QGIS the MOLA data is at a completely different location and very small in comparison. I downloaded ...
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448 views

Compare a DEM and DSM with QGIS

I have a DTM with 40cm resolution and a DSM with 2cm. Now I would like to compare the two so I can identify vegetation that is higher than a certain distance from the ground. I changed the pixel size ...
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155 views

Hillshading for small, flat areas in QGIS?

I have a grid of approximately 172 points with elevation heights for one mound on a flat land. The surface of the mound is 200x200 meters, and the height towards the center is 3 meters. I did TIN ...
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439 views

Cell size in Mosaic to New Raster versus Resample cell size

I have several TIF 2 meter LIDAR DEM files (100+) that I am merging into a single raster and then creating 4m, 6m, 10m, and 30m DEM raster variants. I would normally just use the Mosaic to New ...
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66 views

Merging DEM file generted many negative value in QGIS

With four DEM files downloaded by Python Elevation package, I merged them in QGIS 2.8.3. I use raster-> Miscellanaous -> Input direction, no more attribute was added. The four dem data has ...
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50 views

Rows and columns too high

I currently have a 5m DEM with 6000 rows and columns. I need to keep the spatial resolution but reduce the number of rows and columns to 1000. I have used the basin tool to separate the DEM and ...
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84 views

Reproduce a raster with same cell size but different no of columns and rows

I have a DEM raster of 200m resolution, the no of columns and rows are 2458 and 2845, I want to reproduce this raster in a way that the cell size remains the same i.e. 200,200 but the no of columns ...
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288 views

Resampling using gdalwarp gives me no data

I have an image with the following information. Driver: GTiff/GeoTIFF Files:test_DEM.tiff Size is 91, 73 Coordinate System is: GEOGCS["WGS 84", DATUM["WGS_1984", ...
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33 views

Applying values to highest terminal segments in channel network using PostgreSQL?

I extracted a channel network from a dem but due to some technical difficulties the layer had some discontinuities. So after filling them, i suddenly realised that the Strahler orders it gave me were ...
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306 views

Hillshade effect not working when no data is on screen

I'm working on a DEM and I selected hillshade effect to be active. The problem is that I can't get it to appear when a no-data area is shown on my screen. If I move the area just enough for the no-...
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207 views

Is it valid to resample a raster from 1m to 3 feet?

I know that in general it is not a good idea to up-sample. I am curious if it would still be be a "bad idea" with a minor change like this from 1m resolution to 3 feet? Going to 3 feet would not ...
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56 views

Zonal smoothing on a specified area of a raster?

Is there any way to smooth a specify an area on a raster, such as a DEM, and smooth it? For example, I'd like to smooth out the artifact highlighted in the red box. What is the best course of ...
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71 views

Ideal minimal area for watershed automatic delineation using DEM SRTM

I need to do a bunch of analysis on a city using for that, watersheds . As smaller the watersheds are, better are quality of my work. Due to the vertical accuracy of SRTM DEM, I know there are some ...
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860 views

Creating a Greyscale DEM from Multiband (RGB) GeoTIFF in QGIS

I'm trying to merge some river bathymetry with LiDAR from the surrounding riverbed using QGIS 2.14.0 Essen. The river bathymetric data is a GeoTIFF, and it comes with a separate scale associating the ...
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375 views

DEM / Basemap Alignment

The image below shows the problem I'm facing. I'm trying to align a DEM with the ArcMap Imagery Basemap. Unfortunately, I can't make them to perfectly align. I tried changing the coordinate system to ...
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38 views

Creating tiling scheme to get multiple extents before gridding elevation data

Looking to create 1 degree by 1 degree tiles with pixel overlap to get extents before I start gridding. So basically I would like to have a shapefile of the tiling scheme with extents before having ...
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155 views

Generating continuous aspect surfaces from DEM with QGIS

I'm trying to extract aspect surfaces from different DEM sources at different resolutions in QGIS. I've had success working with SRTM-derived grids (3-arcseconds) and am trying to perform the same ...
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38 views

Inserting ground control points in ASP NASA?

I am using PLEIADES stereo images and  the Nasa software : Ames Stereo Pipeline (ASP) in order to generate a Data Elevation Model (DEM). In addition to that, I have some ground control points and I ...
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94 views

Turning simple raster file into DEM?

I'm using QGIS LYON 2.12.1, and I want to turn a plain gray scale raster file (that I got from Google search) into a DEM. The aim is to apply the DEM (terrain models) function to the newly created ...
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455 views

Why does the flow direction tool in ArcGIS desktop give wrong output (unique values from 1-255)?

I ran the flow direction in ArcGIS, and received unique values ranging from 1-255. I know that these values are wrong, and should be along the lines of 1, 2, 4, 8, 16, etc multiples. The DEM is ...
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321 views

Calculating flow distance of pixel from outlet using R?

I have created these raster files for a river basin: DEM Flow Direction Flow Accumulation Also, I have another raster with values of rainfall. All the 4 rasters have same spatial extent, ...
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176 views

QGIS - .vrt DEM layer only partially goes to hillshade

I am using QGIS 2.12 on Macbook Pro running on Mac OS X Yosemite 10.10.5. I have six adjacent DEMs of the 7.5-minute quadrangle size (National Elevation Data or NED, I think). I loaded them into a ...
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131 views

Calculating aspect in flat areas in ASTER DEM with ArcGIS for Desktop?

I have an analyzed aspect surface from ASTER DEM 30m resolution in ArcGIS 10.2. But it shows many aspects in flat area.Normaly it must calculate this are as flat (-1). How can I resolve this problem?
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150 views

How to extract area information from a raster based on a DEM or contour lines

I have a raster representing the distribution of a specific land cover type - the raster values are 1 for where the land cover type is present and 0 where it isn't. I also have a DEM with 5m ...
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69 views

Mosaic DEM has large pixel when displayed in ArcMap?

I created a mosaic dataset in ArcMap 10.2 from tiles of ASTER DEM's at 30m resolution. I am attaching the image of what my export looks like. You can see that there are extremely large, alternating ...
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75 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 ...
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172 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 ...
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45 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 ...
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87 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?
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128 views

How to fit Google Earth satellite image to UK OS 50 DEM

I have extracted a DEM tile from the UK Ordnance Survey's free OS Terrain 50 dataset The tile contains spot heights for a grid comprising 51 nodes (West to East) by 51 nodes (North to South) with ...
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81 views

Managing or Reducing noise in a mosaic raster

I have created a raster with the Mosaic to New Raster tool from 3 separate rasters. However in my mosaic I have some consecutive pixels which seem to be the noise of the previous procedure. Is there ...
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180 views

Ignoring certain values when creating profile graph in ArcGIS for Desktop?

I have a statewide DEM I am trying to create a profile of, however the DEM has some areas of widely varying size (bodies of water) where data was not collected and these areas were all filled by my ...

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