Questions related to slope analysis.

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11
votes
2answers
3k views

How to calculate average slope in a grid?

This is actually a two part question: Which methods are there to calculate average slope by unit (say km²) for a given area? Are there any special requirements on the data - like additional ...
10
votes
3answers
2k views

Calculating mean slope: Harmonic or Arithmetic Mean?

I have to calculate the average upslope percent slope for a large dataset, the basic method is detailed here. However, I've begun to wonder if harmonic mean might be more appropriate than the ...
7
votes
3answers
214 views

Calculate average stream slope at each location along stream

I'm trying to calculate the time of concentration for every point along a stream network. To calculate the time of concentration, I need the upstream channel length and channel slope. I've been able ...
6
votes
2answers
174 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 ...
6
votes
1answer
186 views

Directional slope calculation

I'm trying to generate rasters of slope and curvature of an elevation DTM. The particularity is that i need to be able to specify the direction (e.g 180, 270 degrees)in this calculation. I am using ...
6
votes
2answers
2k views

Calculating average slope along line using ArcGIS Desktop?

I have a slope layer and I want to calculate the average slope along a line. This line isn't necessarily straight (e.g its a route, I would like to be able to input geographic coordinates along that ...
6
votes
1answer
124 views

Calculation of surface derivatives at the edge of the raster

I was wondering how does ArcMap10.2 calculate surface derivatives (slope, aspect) at the edge of the raster, since the Horn algorithm is used and uses the 8 neighboring pixels around each pixel. When ...
5
votes
2answers
2k views

Calculating slope cell-by-cell in ArcPy?

I am relatively new to the ArcGIS-Python environment and want to calculate elevation raster slope. But it says "ValueError: setting an array element with a sequence". Below code is what I have. ...
5
votes
3answers
992 views

How to calculate changes in slope angle between cells/areas?

I am doing an estimation of erosion with ArcGIS. I use the UniversalSoilLossEquation (USLE) for this. Now, i want to calculate the L-factor of this equation. I need the FlowLength for this. My ...
5
votes
1answer
7k views

Calculating Topographic Wetness Index (choosing from different algorithms)

Topographic Wetness Index can be expressed as Ln(a/tanB) based on the idea of Beven and Kirkby (1979) where a is the spesific catchment area (a=A/L, catchment area (A)divided by contour ...
5
votes
1answer
3k views

How to calculate polygon area considering slopes?

I am looking for an accurate algorithm or a service to calculate surface area on earth where points are calculated on the basis of GPS Coordinates. I am using Google Map Api version 3 and are drawing ...
5
votes
2answers
104 views

Compare slopes between adjoining line segments

Using a DEM, I assigned slope values to individual segments in a street network feature class. In some areas the slope values seem suspect, such as where a highway overpasses a local road. Is there a ...
5
votes
2answers
335 views

bicycle / bike map road grade markers - semi-automated?

So I'm making a bike commuting map for our area, and one of the features to show (common on a lot of bike maps) is some type of road grade marker. We're planning to show three categories: 'kinda ...
4
votes
1answer
274 views

Identifying south facing mountain land, above an elevation, within a slope range, less than fixed distance from major roadways

This odd question comes from believing that such an analysis is plausible in a GIS system. Only, I don't how to accomplish the various discrete steps implied from the Title, nor where to get a topo ...
4
votes
1answer
1k views

How is slope of a surface in an arbitrary direction produced?

I am currently developing a program that requires that I calculate the slope for each cell in a DEM. However when I try to understand the algorithm to be used I get stuck trying to understand exactly ...
4
votes
2answers
1k views

Querying slope data using raster calculator: why are all results true?

I am using ArcGIS 10.2.2. From a DEM, I have created a new raster showing slope using the slope tool. The color scheme was automatically classified into 9 tiers. What I want to do is query this raster ...
4
votes
1answer
252 views

How do I use a DHM in tiff format for distance and slope measurements?

I am a student and I have to work out a project about soil loss on a plot. I need basic measurements of this plot such as length, width, area and slope for my erosion calculations. I have got my ...
4
votes
2answers
106 views

Faster way to calculate slope between two points on DEM using ArcGIS for Desktop?

I'm a forester, and I do lots of work with LiDAR derived DEM's. I'm looking for a quick-and-easy tool to calculate the slope between two points. The application for this would be drawing a proposed ...
4
votes
3answers
236 views

How to resample a 30m DEM to a 100m slope raster properly?

I need to resample a 30m DEM to a 100m slope raster. Do I just resample the 30m DEM directly to the 100m slope raster? or, do I convert the 30m DEM to a 100m DEM and then create a 100m slope raster ...
4
votes
1answer
202 views

How to use SRTM Global DEM for Aspect calculation?

I need to derive a raster representing aspect for North America (from STRM data, originally in geographic lat/long). In most projections, true north is only map north along eg the central meridian so ...
4
votes
1answer
766 views

How to compute average slope and area-weighted average slope?

I am learning GIS for use in hydrologic analysis. Related to computation of overland flow there are two types of slope that I would like to be able to obtain from GIS. The first is average slope for ...
4
votes
1answer
62 views

How do I consider entity alignment against slope direction?

I am a newbie to QGIS and don't know if the following is possible so would be grateful of any thoughts. I have a hill, most of which is given over to rectangular pasture fields. I hypothesize that ...
3
votes
2answers
91 views

How to calculate the relative share of an area of a circle that has a slope >15% in Germany

I need to calculate the share of buildable land for the 15 major german cities within a 50 kilometer radius of the city center. Part 1 of the definition buildable is that the area must have a slope ...
3
votes
1answer
287 views

How to subtract out the slope (in general) of a DEM?

I'm searching for a solution process to subtract out the slope of a DEM like this: I have a high resolution DEM and want to reconstruct historical/old/not active parts of a river. The problem is ...
3
votes
2answers
113 views

Fixed distance between two contours - Qgis 2.14.1

There is a possibility, when you select a contour line and give a fixed length of line, this line connects automatically to the next contour lines? I have two other questions on this subject but I do ...
3
votes
1answer
37 views

Creating groups containing slopes of a specific range

I have a basic knowledge of QGIS and can do everything I need to do to achieve my requirements except the following. I'm trying to graphically show areas of land that contain a set of specific slope ...
3
votes
2answers
258 views

Matching vector network to slope raster dataset in ArcGIS for Desktop Advanced 10.1

I am trying to calculate the average slope of a rivers network. Each part of the network is broken up into individually numbered segments. I have a high resolution slope raster and thought I could ...
3
votes
1answer
448 views

Calculating Mean Upslope slope, curvature, etc

I'm trying to generate rasters whose values summarize the mean value of a given parameter (slope, curvature, etc.) of the upslope terrain. I feel like this should be doable using only a flow ...
3
votes
1answer
105 views

What function should I use to assess the degree of elevational change (rocky cliffs etc.) of a DEM?

I have a DEM of my research area and I want to assess how the topography/elevation changes. I am specifically looking to see what areas may be good suitable bat-roosting habitat so I am trying to ...
3
votes
1answer
221 views

Compute global DEM topographic indices and compromise projections

I would like to compute global topographic indices based on SRTM elevation data. These indices are computed along river/channel networks extracted from a DEM and are a functions of both local slope ...
3
votes
1answer
325 views

How to display the slopes that only facing west using ArcGIS for Desktop?

Here is what I am struggling with ... In ArcGIS for Desktop I have to Derive and symbolise areas considered susceptible to avalanche risk based on the following simple rules: areas with a slope ...
3
votes
1answer
72 views

ArcPy Slope Script - Trouble Saving

I have an ArcPy script that applies the slope function to raster files in ArcGIS. I tried running the script with two raster files in the table of contents, and the script runs, but only saves one ...
3
votes
0answers
30 views

How to re-slope a given DEM to pre-determined slope in ArcGIS?

I have a set of topographic contours of a mine and like to re-slope those areas alongside the river to a pre-determined slope, say 22˚; and 27˚ for water pond wall. The existing slopes along the river ...
3
votes
1answer
137 views

Wrong direction in r.watershed slope length calculation?

Or have I completely misunderstood something now? As a programmer I took it for granted that the row number would change if I traversed the map up and down in the program along the North-South axis ...
2
votes
4answers
970 views

Error When Trying to Run Slope Analysis Script

I have written a script which is supposed to loop through all the rasters in a folder and perform a slope analysis on each raster and save the results in another folder. I keep getting the following ...
2
votes
3answers
3k views

Calculating slope in percentage with QGIS

I'm working with QGIS, v. 2.0.1. I have several soil types. They are (amongst others) described with slope indications. I already calculated the slope from the DTM in degrees, but as description of ...
2
votes
3answers
4k views

Creating a Slope Map Using Contours

I am trying to create a slope map. I have many contour elevation files. I tried to use the slope tool in Arctoolbox, but it calls for raster files and I'm working with vector data. Any help with this ...
2
votes
1answer
232 views

SRTM DEM with 16 bit signed pixel type changes to 32 bit float when creating slope/aspect/curvature

I have mosaiced 8 SRTM DEM tiles in order to get one raster layer of elevation. When I use "Mosaic to New Raster" tool I set as a pixel type format "16 bit signed" because this is the format that SRTM ...
2
votes
2answers
883 views

Calculate Slope Between Pixels Through Time: A Time Series Trend Analysis

I have a 9 year weekly time series (~500 raster grids of equal cell size and extent). I'm interested in obtaining the regression line slope between pixels (Imagine stacking all 500 grids on top of ...
2
votes
2answers
990 views

Toblers's Hiking Equation and Slope Dilemma

I'm trying to use Toblers's Hiking equation to determine economical backgrounds of some hillforts. The equation is anisotropic which means that the speed of movement that it calculates differs whether ...
2
votes
2answers
342 views

Arcpy Slope Analysis Script

I'm trying to run slope analysis in ArcGIS. I have written an ArcPy script that converted feature layers to raster files. Now I have a list of rasters (each with a unique name) in the table of ...
2
votes
1answer
162 views

How to disassociate roughness from slope

How to measure topographic roughness irrespective of slope in ArcGIS? I have used many methods to generate roughness layers, including TRI, VRM (which is supposed to be less correlated with slope), ...
2
votes
2answers
2k views

Calculate Slope of Street Segments

Using a DEM, I need to assign slope to individual segments in a street centerline feature class. It will be used to account for increased travel time for steep slopes in a network analysis. I am ...
2
votes
1answer
455 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 ...
2
votes
1answer
131 views

Slope tool gives wrong degree values

I am trying to create a slope map in ArcMap out of a DEM. I used the Slope Tool (Spatial Analyst), selected my DEM as input and degrees as an output result. There I got the message that "The Z units ...
2
votes
2answers
267 views

What is the “best” way to automate the GIS slope and aspect algorithm?

I am currently obtaining slope and aspect of roofs using ArcGIS as follows: Mosaic several Lidar .asc files to new raster Extract by mask using Mastermap building outlines to get hold of just the ...
2
votes
1answer
279 views

QGIS has an automatic way of finding the LS factor?

I wonder if is possible to calculate LS (soil erosion) factor automatically in QGIS? Or at least a way to calculate the length slope?
2
votes
1answer
589 views

Error when slope creating using ASTER 30m DEM

I have tried to create a slope map using ASTER 30m DEM obtained from internet. But when I use it to create (using ArcGIS 10 & 3D Analyst) a slope raster, the output is only 0-89 range. My ...
2
votes
1answer
2k views

What angular units does the QGIS raster calculator use: Degrees, Radians, Gradians?

I am working with QGIs and am converting a slope raster with values in degrees to a slope raster with values in percent using the raster calculator and the following formula: ...
2
votes
1answer
98 views

Calculating slope for points with downhill slopes rendered as negatives in ArcGIS

I have a DEM and a series of points. I'd like to measure the change in slope along the series of points. Distinguishing between uphill and downhill slopes matter to me, and ArcGIS' slope function ...