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Geographic Information Systems

Questions tagged [slope]

Use this tag when asking questions related to slope analysis.

250 questions
info Newest Frequent Votes Active Unanswered
0
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1answer
25 views

Slope is not consistent with the elevation of DEM and seems to be incorrect

I have a DEM image which shows the elevation is from approx. 81 to 103. I expected the slope should be 0-22m. However, the result from DEM-Terrain Model-Slope is from 2.5 to 13.2. Anyone knows why?
0
votes
0answers
21 views

GdalDEM slope error in Jupyter

I try to calculate slope data. This is the DEM source https://www.earthenv.org/DEM Firstly, I translate data with gdal.Warp according to image UTM zone. Original image .bil extension so first I ...
0
votes
1answer
52 views

Estimating slope by fitting a quadratic surface (Evans 1980) in ArcGIS Pro

I am needing to calculate slope using the quadratic surface method of Evans (An integrated system of terrain analysis and slope mapping, 1980), but not sure how to implement it in ArcGIS Pro. A GRASS ...
1
vote
1answer
44 views

LS Factor in SAGA (slope units)

In which units do I have to calculate Slope to use as an input for the LS Factor tool in SAGA (degrees, %, radians)? I couldn't find anything in the documentation.
3
votes
1answer
57 views

Strange output from QGIS Raster Terrain Analysis plugin

This is closely related to several other questions on this site: here, here, here etc. However, my issue is not resolved by following the answers provided. I am using the Raster Terrain Analysis ...
1
vote
0answers
38 views

Calculating maximum extent of debris flow from point with mean slope value

At a very large scale I perform a spatial analysis for which I have to apply mean slope criteria. These criteria allow me to calculate the maximum extent of an event (debris flow). I know that below a ...
1
vote
1answer
43 views

How should I interpret R terrain/slope output in degrees?

I'm calculating the average land gradient (in degrees) in Brazil and I do not know how to interpret the results. As I'm calculating the slope in degrees, 0.25 is 0.25 degrees, 25 degrees or should I ...
1
vote
1answer
21 views

Creating slope map with ArcGIS Desktop?

I created slope map with DEM model in ArcGIS Desktop. But it is only categorize in to two sections. I think it is problem with the horizontal and vertical scale. I used WGS84 coordinate system. How ...
0
votes
0answers
16 views

Calculate average slope values for a point using 50ft vector perpendicular to contour

I am trying to calculate the average percent slope of a hillside on either site of a data point. I tried extracting info from a DEM using a radius around the point, but I believe a more accurate ...
1
vote
1answer
32 views

Statistics of slope in individual polygons (asset) on Google Earth Engine

I have a single shapefile with multiple polygons, uploaded to GEE as an asset. I am trying to find the mean slope (using SRTM elevation imagery) in each of the polygons, on GEE. However, I get only ...
0
votes
0answers
51 views

Slope rasters - different results from different tools

I'm calculating Least Cost Path (LCP) within QGIS 2.18. The first step is to produce the slope raster from the DEM. Using r.slope in GRASS produces excellent results where I can go on and finally ...
0
votes
1answer
40 views

Convert slope file to calculate the percentage of the coverage

I calculated the Slope of the area that I'm working on, and I was wondering if there is a way to calculate the actual percentage of each bracket, meaning the percentage of contribution of each class. ...
1
vote
1answer
67 views

Converting RTK Elevation Data to DEM?

I have a shapefile that contains elevation data. I want to eventually convert this to a slope layer. I'm assuming I have to convert to a raster, then a DEM, then slope. Is that correct? If so, ...
1
vote
0answers
16 views

QGIS/GRASS: forecast slope variation in slope by a new road

For preliminary project purposes, I wonder if there is a way to forecast and calculate with QGIS and/or GRASS the variation of slope dued by new road, starting with terrain DEM and a project sketch of ...
2
votes
1answer
55 views

What the default unit in QGIS 2.18 $area is calculated and etc?

I'm a beginner in QGIS . We are using 2.18 version. What are the basic units for area and slope, etc? SI, so means m, m^2, °? Or I can set it by myself? If it's possible to set it, where?
0
votes
1answer
134 views

Creating polygons of specific slope percentage from a slope raster in QGIS

I am trying to extract all areas where the slope is greater than 20% and then turn those areas into a polygon. I'm using QGIS 3.0.2.
4
votes
1answer
57 views

Service Area (ArcGIS), including slope as a cost

I'm trying to make a service area network analysis containing the time that is needed using a bike starting from one point. The attached map shows this service area when the bicycle speed is 20km/t, ...
0
votes
1answer
374 views

Calculating slope/gradient from longitude and latitude

I've recently got some field erosion data. The only geographic data I have is the (lon, lat) (in degrees). I need to plot the erosion against the slope, however, I do not have the slope yet. Is it ...
1
vote
0answers
114 views

QGIS - Lookup elevation or slope from geoTIFF from a series of lat/lon values

I have a geoTIFF file (pretty large) covering a good chunk of Spain around Almeria. I got it from the EU-DEM v1.1 data (25m resolution), freely available in which I have a route in lat/long and I want ...
1
vote
0answers
72 views

Edit a raster (DEM) to create a constant slope angle

I'm trying to edit a raster (DEM) that has square sides (90 degrees) to create a surface with a constant slope angle of 18 degrees. I'm working in QGIS and have not been able to find any help for ...
-1
votes
1answer
21 views

Unwanted artefacts working with Raster analysis

I am trying to make a simple slope map from a DEM (tif). I already tried with the different slope-tools in QGIS (GDAL, SAGA, GRASS) and also the 3D Analyst in ArcMap. Boths bring the same result: a ...
0
votes
1answer
17 views

How to define the angle of points on slope?

I have point data set and DEM and my task is to identify how many points are falling on the slope of more than 40 degrees. How could I do this in ArcMap?
0
votes
0answers
31 views

Why is my aspect not displaying the full data?

I am trying to get the slope aspect for the altitude shown above. Can someone please advise me on why this may not be working properly?
0
votes
2answers
179 views

Issues with QGIS Slope Analysis

Having issues with slope analysis. I click raster, analysis and then slope. I enter my input and output and run the tool. The output I get doesn't appear to have been calculated correctly. Instead of ...
0
votes
0answers
13 views

Mosaic multiple slope files

I am trying to mosaic multiple slope files into one large slope file. What is the best tool to use? I have tried mosaic to new raster but the values change from multiple decimal points to whole ...
1
vote
1answer
69 views

Generalizing slope raster in Mapinfo?

I am working on calculating a slope raster in Mapinfo using a 15cm DEM derived from a LiDAR point cloud and the output data will have 3 predefined breaks displayed so I need to blur those relatively ...
0
votes
0answers
28 views

Specifying width of least-cost path in ArcGIS Spatial Analyst?

I am performing a least-cost path analysis using ArcMap in an area with high slope variation. I am working with a 0.5x0.5m raster to prevent generalization and elimination of danger slopes. I need a ...
0
votes
1answer
113 views

Slope Classification for HRU in a watershed (SWAT Model)

For the definition of HRU (Hydrological response units), the parameter slope can be classified into maximum of 5 classes. Depending on the definition the results will vary. Is there a commonly used ...
1
vote
1answer
89 views

Changing DEM resolution when creating a slope raster? [duplicate]

I want to create a slope map using a LiDAR DEM. I think that I should use the slope tool; but I need a slope map with a 2m resolution and I'm not sure how to do that. How can I have a slope map with ...
0
votes
1answer
45 views

Slope and mosaics

I have used a large number of Gtopo30 altitude tiles and used the mosaic tool to create a large DEM for my area of interest. I am trying to get a slope for said area but when running the slope (...
0
votes
1answer
60 views

How to create a surface with a slope of 2%?

I am working on a project where I have a polygon of a basin that I should create his base whose elevation begins at -1m and go down in every direction with a slope of 2%. Does anyone know how to do it ...
2
votes
0answers
72 views

QGIS: How to find a line with defined slope starting from a point over a DEM? [closed]

If I have a DEM as raster layer and a point with defined position in a point layer, how could I generate a line with defined slope of e.g. -1%? The end point can be anywhere and should be defined by ...
0
votes
1answer
72 views

Selecting a subset of a raster, based on aspect and slope, as input to calculate area

Background I created some digital elevation models and subsequently made a 2 layer raster for each containing the calculated aspect and slope using raster::terrain. Now I want to calculate the area of ...
4
votes
2answers
84 views

Is inverting slope map same as invert surface?

Is it possible to invert a slope map same as invert a surface? I found code on this website https://support.esri.com/en/technical-article/000006694 The code is following: (([elevgrd] - Z_Max) * -...
7
votes
2answers
186 views

Prevent SAGA in QGIS 3.0 from creating certain outputs?

I'm wondering if there is a way to prevent SAGA from generating temporary files. For example, if I just want to generate a slope map using SAGA I have to wait for all 11 other grids to get processed. ...
1
vote
0answers
79 views

Setting maximum slope/flow length in flow accumulation using SAGA?

I like to limit the slope length in SAGA GIS. In other words, the flow accumulation should only account for a specific length until a subsurface flow initiates and surface flow stops. Actually, I ...
0
votes
0answers
47 views

How can I project a raster DEM and not get serious distortion in the resulting DEM?

Please see this link to see a fine example of what I am dealing with. Distortion in projected raster My specific situation is that I have downloaded DEM data from the National Map (USA) and it comes ...
1
vote
0answers
79 views

QGIS/GDALDEM SLOPE Output Has Contoured Or Terraced Texture

I have been trying to greatly reduce or eliminate the contour-like texture that appears in my output from gdaldem slope. The image, below, demonstrates this textural effect. The texture of the ...
0
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0answers
161 views

Understanding Slope Line and Flow Direction in ArcGIS Desktop?

I would like to create a Flow Direction (Polyline - not raster) which needs to follow slope direction (as arrow in picture I attached) I'm working in mike urban (SWMM Model) and the software assign ...
2
votes
0answers
67 views

“two ways” Reclass QGIS

I'm a forestry technician and I've one question dealing with forest road planning... in order to calculate areas that can be cover by a specific machine (with a given work distance) I do as follow: "...
3
votes
1answer
82 views

Conditional Statement (CASE-WHEN) in QGIS for slope aspect

After processing a DEM with a mask to get the aspect values of some polygons I would like to create a new field classifying those values as N, NE, E, SE, S, SW, W, NW. I've written this but I can't ...
1
vote
3answers
695 views

Exporting slope raster for entire country in GEE

I have loaded SRTM (30m resolution) DEM data through Google Earth Engine and have determined the slope for the entire country of Peru. When I export the image out into Google Drive, I get the ...
0
votes
1answer
126 views

Determining Upslope and Downslope from Line Features to Map Hydrologic Capture Zones

I am trying to map hydrologic capture zones (HCZ). HCZ's are contributing areas upslope of any potential capture feature (i.e. road, pipeline path, railroad line), that would alter/impact the natural ...
1
vote
0answers
56 views

Creating a bottom-top aggregated slope model in QGIS

I have a Slope model and would like to create a bottom-top aggregated slope model across a waste dump. So I am looking at creating this through the slope's mean values. One approach I thought of was ...
1
vote
1answer
475 views

Calculate slope of line segments with QGIS

I want to calculate the slope of a forest road in mountainous areas. No problem with ArcGIS following the instructions of the following post: (see comment of user 'FelixIP') How do I find the slope ...
2
votes
1answer
359 views

Hillshade shows grid texture artifacts

I tried to make an hillshade and a slope map from a DTM using QGIS but the result shows some artifacts. As you can see in the picture there is a grid texture in the hillshade and the slope map. I ...
1
vote
1answer
152 views

Calculating mean slope of lines based on DEM?

I have a DEM and a line vector shapefile (also available in PostGIS) and I need to calculate the mean slope of every line. Direction of the slope (positive or negative) is not important. That means I ...
4
votes
1answer
285 views

calculate slope of lines between nodes?

I need to calculate the mean slope of roads between nodes with QGIS. I have a DEM and a vector (PostGIS) with the roads, nodes are additionally displayed as point shape and also contain an elevation ...
2
votes
2answers
535 views

How to convert 4band RGB/A GeoTiff to 1band Gray GeoTiif?

I'm creating slopeshade images from a DEM. What I'm doing is: gdaldem slope -alg Horn -s 1 -compute_edges -co BIGTIFF=YES in.tif /vsistdout/ | \ gdaldem color-relief -co BIGTIFF=YES -co TILED=YES ...
0
votes
1answer
154 views

Fuzzify Slope Values

For a suitability analysis I need to define the suitability of slope from DEM values (in %) to build new trails. Knowledges says that flat and rather steep areas are not suitable due to water runoff. ...

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