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16 votes
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Calculate slope of line segments with QGIS

In the QGIS Processing Toolbox, there are GRASS tools v.split.length and v.drape (using QGIS 2.18.16). Before starting; 0.) make sure your DEM and road data are projected onto the same CRS. Then, ...
Kazuhito's user avatar
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13 votes

How to perform a slope analysis in QGIS?

Slope analysis is performed on a DEM (raster layer with elevation values). This is one way to do it. If your contours have an elevation value, you can use the interpolation option (raster/...
Gerardo Jimenez's user avatar
13 votes

Slope, in which direction?

The direction of a Slope is known as its Aspect. It's usually defined as the direction the slope "faces", to me that's a little ambiguous and it's more intuitive to think of it as the "downhill" ...
Dan C's user avatar
  • 12.2k
13 votes

Hillshade shows grid texture artifacts

The problem is because the DTM has a high-resolution pixel size when data (in my opinion) doesn't have the same resolution is some areas. For example, direct hillshade raster: Check pixel values (...
aldo_tapia's user avatar
  • 13.5k
13 votes

Calculate slope of line segments with QGIS

This is a modification of Kazuhito's answer using native QGIS algorithms using QGIS 3.12. In the QGIS Processing Toolbox, there are the tools Split lines by maximum length and Drape (set Z value from ...
Baswein's user avatar
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12 votes
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What is the default unit for slope in QGIS?

If you create a slope layer from Raster > Terrain Analysis > Slope, the output layer will have degrees as units of measurement. Instead, using the Slope GDAL tool from the Processing Toolbox will ...
mgri's user avatar
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10 votes
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Average Cross Slope Calculation

Contours do not cross each other, so I cannot explain it using your example. Instead, let me illustrate what this ACS does by a picture below. Looking at the pictures [1] and [2], you will find steep ...
Kazuhito's user avatar
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10 votes
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Getting x, y, slope in raster, using QGIS

You can use the algorithm Raster Values to points (or Raster Pixels to points Documentation link). Once the point layer is created you could export it as a csv file :)
wanderzen's user avatar
  • 2,110
9 votes
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Calculating average stream slope at each location along stream using ArcGIS Desktop?

As @Hornbydd pointed it is network searching problem. I suggest the following workflow: find source points of the streams sort them in descending order by flow length In the picture below 139 green ...
FelixIP's user avatar
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9 votes
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Finding pixels in DEM with 5% slope or less?

You mention 3D Analyst so I am assuming you have ArcGIS. Use the tool ArcToolbox-3D Analyst Tools-Raster Surface-Slope to create a slope surface from your LiDAR data. Use the tool ArcToolbox-3D ...
GBG's user avatar
  • 9,654
9 votes

How to get the slope from an elevation raster in QGIS?

It looks like you are not using a digital elevation model (DEM) data. It is just an image (scanned image) from layout or something and not a real elevation data. You need to use elevation data such as ...
ahmadhanb's user avatar
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8 votes
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Strange output from RSAGA topographic wetness index?

I think I see the problem. I could reproduce this, both using your script, and SAGA itself. The output from SAGA matches the output from your script. So it's not RSAGA. But look at the slope output ...
Steven Kay's user avatar
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8 votes
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Rotating symbols per attribute value in QGIS?

If you want to use a field in attribute table, you should select the field directly in the Data defined override which has the angle value. The field should be of double/integer type not string field ...
ahmadhanb's user avatar
  • 40.7k
8 votes
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Drawing slope signature in QGIS

Automatic solution I created a model that automatically creates the lines as you want as a layer style. Run the model, make the inputs and you get the style you want. Details about how I did it: see ...
Babel's user avatar
  • 70.6k
7 votes

Calculating relative share of an area of circle that has slope >15% in Germany

Doing this kind of processing is pretty straight-forward, but there are some tricks along the way that will determine how accurate your analysis will be. Your data will be generated from a slope ...
Roberto Ribeiro's user avatar
7 votes

Calculating slope direction in QGIS?

I found tool for this. That is Saga plugin called: Gradient vector from surface. And result is: you have to choose in style manager, arrow for lines
Frodo's user avatar
  • 2,407
7 votes
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Conditional Statement (CASE-WHEN) in QGIS for slope aspect

If the Aspect raster converted to polygon or you have a shapefile with "Aspect" field name in the attribute table and you need to put the text definition, then you are almost there, but you need to ...
ahmadhanb's user avatar
  • 40.7k
7 votes

Prevent SAGA in QGIS 3.0 from creating certain outputs?

Should be possible to do if you feel like hacking your qgis install. look for this file in your qgis install: https://github.com/qgis/QGIS/blob/master/python/plugins/processing/algs/saga/description/...
ndawson's user avatar
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7 votes

QGIS slope output problems

The herringbone pattern in your image is a classic indication that a Nearest Neighbor resampling occurred somewhere in your workflow. I suggest that you go back through each processing step and ...
Stu Smith's user avatar
  • 8,212
6 votes
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Calculating relative share of an area of circle that has slope >15% in Germany

You can download a European-wide DTM from the European Environmental Agency Or use other open DTMs of Germany like this As your calculations are in SI units, you should probably use a projected grid ...
HDunn's user avatar
  • 8,616
6 votes
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Calculating slope direction in QGIS?

You can generate the slope in several ways: Raster -> Analysis -> DEM -> Slope. Or via slope functions in the Processing framework (r.slope.aspect). Run it on your DEM. Do the same for the aspect. ...
lynxlynxlynx's user avatar
  • 4,222
6 votes

Information about algorithm used by Terrain models

There is good documentation on all aspects of GRASS internals, including references to literature. So see the documentation on r.slope.aspect. Unfortunately I find it difficult to get this level of ...
alphabetasoup's user avatar
6 votes

Creating slope map from DEM using QGIS?

In QGIS (build 2.16.2) there is a function for this build in, as is the case in many GIS programs, which calculates the slope for you. In QGIS this tool can be found under 'Raster'-> 'Terrain ...
Tins's user avatar
  • 506
6 votes

Calculate slope of line segments with QGIS

There is a new QGIS plugin called Road Slope Calculator that seems to do this. Quoting its project description: This algorithm is used to calculate the longitudinal slope of forest paths and roads, ...
tinlyx's user avatar
  • 11.1k
6 votes
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Changing DEM resolution when creating a slope raster?

Before creating your slope layer (Slope tool is the right choice) you can use the Resample tool to change the cellsize of your input raster, without changing the rasters extent. It is however ...
blabbath's user avatar
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6 votes
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Obtaining slope and aspect for points in QGIS

Run the following QGIS Processing Algorithms against your DEM: Slope Aspect Once you have your newly generated Slope & Aspect rasters, run the Point Sampling tool against each to retrieve your ...
Saijin_Naib's user avatar
  • 2,719
6 votes

Determining homogenity of flatroofs based on digital surface model / slope layer using QGIS

You could run "Raster pixels to polygons", to convert your raster to a vector layer: Make sure your Buildings have a unique id, then run "Intersection" with your Buildings: So ...
MrXsquared's user avatar
  • 33.9k
6 votes
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Draw buffer around points considering slope in QGIS

Not sure about the math, but the steps before it should work. I'm using 50 m buffer radius. Calculate a aspect raster Calculate a slope raster Sample raster values twice to get aspect and slope as ...
BERA's user avatar
  • 71.4k
5 votes

Slope layer with false results in QGIS?

As mentioned in comments by user30184 and GerardoJimenez this is due to the horizontal coordinates x and y having a different unit of measurement from the elevation coordinate z. For example, having ...
Andre Silva's user avatar
  • 10.2k
5 votes
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Fixed distance between two contours in QGIS

This may be possible in a manual sort of way using the 'Advanced Digitizing Tools' Using this tool you can specify a distance. Then you just need to set up your snapping options to snap on ...
Knightshound's user avatar
  • 4,430

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