16
votes
Accepted
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, ...
- 31k
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" ...
- 12.3k
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 (...
- 13.8k
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 ...
- 2,346
12
votes
Accepted
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 ...
- 16.3k
10
votes
Accepted
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 ...
- 31k
10
votes
Accepted
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 :)
- 2,130
9
votes
Accepted
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 ...
- 10.2k
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 ...
- 41.2k
9
votes
Accepted
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 ...
- 73.8k
8
votes
Accepted
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 ...
- 41.2k
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
- 2,407
7
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, ...
- 11.1k
7
votes
Accepted
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 ...
- 41.2k
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/...
- 27.8k
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 ...
- 8,314
6
votes
Accepted
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.
...
- 4,257
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 ...
- 8,828
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 ...
- 506
6
votes
Accepted
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 ...
- 975
6
votes
Creating polygons of specific slope percentage from a slope raster in QGIS
I assume that you created slope percent image from the DEM data and I will start from there. You can extract the slope percent that are greater than 20% using the following workflow:
Load the slope ...
- 41.2k
6
votes
Accepted
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 ...
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 ...
- 35.2k
6
votes
Accepted
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 ...
- 76.2k
6
votes
Calculating slope using the 3*3 window approach for elevation data
Here is a shotgun answer, detailing four common methods in deriving terrain attributes. Since you do not indicate a language nor software this is provided in a matrix index context. In an application ...
- 32k
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 ...
- 10.3k
5
votes
Accepted
Slope calculations appear to be 90 degrees off in ArcGIS 3D Analyst?
I think your error is a result of performing a slope calculation on a DEM that isn't in a projected Coordinate Reference System (CRS). The reason for performing a transformation/warping of your DEM is ...
- 1,398
5
votes
Accepted
How to understand/interpret slope unit values in QGIS 2.14?
QGIS slope result is in degrees. From the official doc :
Slope: Calculates slope angle for each cell in degrees (based on first
order derivative estimation).
- 5,679
5
votes
Finding pixels in DEM with 5% slope or less?
You can take the DEM and run the "Slope" tool in 3D Analyst. It is under the "Surface" Toolset. Choose "percentage" as the output type.
Once you have the "Slope" raster you can run the Reclass tool ...
- 3,786
5
votes
Service Area (ArcGIS), including slope as a cost
In Network Analyst (NA), there is a concept of cost associated with traversing (that is, going through) a road link (edge). Such cost is calculated based on the direction in which a road link was ...
- 30k
Only top scored, non community-wiki answers of a minimum length are eligible