Questions related to slope analysis.

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3
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2answers
136 views

Calculate regional slope from DEM

I need to calculate regional slope for a coastline using a ~500 meter DEM covering a coastal plain and continental shelf where the slope for each grid cell is calculated by defining elevation extremes ...
0
votes
0answers
21 views

Slope calculated incorrectly from DEM

I am using the slope tool to calculate slope from a DEM. I'm getting values from zero to about 1.6%, which I know is much too low for some of the areas in my study site (I believe it should range from ...
1
vote
0answers
45 views

False calculated slope?

After the DEM creation, I wanted to create slope layer. However the result has not satisfied me. I don't think the slope map is correct. Have you ever encountered false calculated terrain map?
1
vote
1answer
24 views

How to find lowest elevation change using raster data and w.r.t muliple polygons

I am trying to complete a spatial analysis which yields areas (parcels of land) which are comprised of polygons (in an attribute table) that correspond to the lowest land slope regions or smallest ...
0
votes
0answers
18 views

Min and Max width of 3D Polygon or Multipatch feature

I am trying to carry out some analysis on a ski hill and need help with getting the right tools. I have created a TIN from lidar data and draped an ortho over the TIN in Arcscene. I have also created ...
3
votes
2answers
144 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 ...
2
votes
0answers
111 views

Connect two contour lines with calculated line length

Is it possible to make a plugin for QGIS like PEGGER for arcview 3.2? Problem is, how to make path over contour lines with a gradient in percent? Formula is: K= e*100/G*M ; K=10*100/0.08*10000=1.25m ...
1
vote
0answers
146 views

3D Polyline by Slope on Surface

I wish to project (continue/extend/whatever) a polyline upslope following a specified gradient along a DEM surface. Is there any way of doing this?
3
votes
2answers
105 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 &...
0
votes
0answers
36 views

Actual slope between two points from raster slope value

We have our own raster map and I have raster pixel slope value on map which is calculated using formula as shown in the link below Pixel Slope Calculation, which is used to show different color as per ...
4
votes
2answers
135 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 ...
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
211 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 ...
1
vote
3answers
2k views

How to create the attribute table for a raster that was produced by the Slope Tool (ArcGIS10)?

I use the Slope Tool (Spatial Analyst Tool – Surface) of ArcGIS10 by ASTER GDEM (that was exported to UTM projection). The program produce new raster (with slope value), but the resulting raster ...
2
votes
1answer
164 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 ...
1
vote
1answer
60 views

How to avoid unexpected values in border of slope raster in QGIS

I have a DEM like After calculating slope with QGIS, it's showing the following result So, how can I remove the unexpected value at the edge of this DEM? Which is showing almost 90 degree values....
7
votes
3answers
227 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 ...
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 ...
4
votes
1answer
833 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 ...
0
votes
1answer
141 views

Calculating slope length using LS-tool

Does anyone know how to get LS-tool mentioned in Zhang et al 2013. https://www.researchgate.net/publication/256938578_Extension_of_a_GIS_procedure_for_calculating_the_RUSLE_equation_LS_factor I tried ...
3
votes
1answer
350 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 ...
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
0answers
40 views

How can I statistically compare the surface slope of 2 different areas?

I could use the statistical tests like t-test and ANOVA, however I am afraid those test will easily show significant differences if I use the slope values of all cells from each area.
1
vote
1answer
35 views

How to assign a value for Slope of Different percent?

I have slope percent varying form 0 to 25 percent. Now I want to give a value for each slope percent. For example, if my slope percent is 2 % , I want to assign a value of 10. As a matter of fact, ...
1
vote
1answer
104 views

Slope analysis of DEM in QGIS?

I have very strange problem with the raster analysis. I have a DEM as a Geo tiff and I do a slope analysis in QGIS. I've done this many times and everything was ok but this time I received reversed ...
1
vote
0answers
33 views

python 2 polygon intersection

I have slope values derived from a DEM which I reclassified into NoDATA and vaules which I need. Then I made a polygon from this raster. I need to do intersection or something like that with the ...
1
vote
1answer
54 views

Select points situated on zero degree slope

I need to choose points from SHP file, which are positioned on raster cells with 0 degree slope. Creating a slope raster from DME is not a problem, but I don’t know how to write a script that chooses ...
2
votes
0answers
84 views

QGIS raster calculator - crash minidump

I'm new to QGIS and using version 2.10.1-Pisa. I have two raster layers created from ASTER DEM data. I have one for slope and want to create a binary layer where only pixels between 8 and 60 degrees ...
0
votes
0answers
86 views

Improve Slope Raster Precision?

Im working with ArcGIS and i have a raster layer created with just four points in XYZ, the plane that forms between these four points has a slope of 10 percent. When using the tool SLOPE (3D Analyst> ...
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. ...
1
vote
1answer
87 views

QGIS slope percent calculation

I'm using QGIS and I'm trying to calculate slope < 20% from a file I have but when I use the raster calculation SLOPE < 20 the result is all black. What am I doing wrong? The data is already in ...
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 ...
0
votes
1answer
112 views

Slope (Spatial Analyst) output shapefile having weird values

I'm trying to calculate the slope for a raster layer using ArcMap 10.2 and the Slope (Spatial Analyst) function. The raster I'm using is an NED 10m mosaic DEM, and the mosaic's datum is in WGS 1984. I ...
0
votes
0answers
28 views

Predicting Potential Areas of Eagle Nests based on Slope and Elevation using Mean +- 1 Standard Deviation?

I am trying to predict Potential Areas of Eagle Nests based on Slope and Elevation using the Mean +- 1 Standard Deviation as the potential range that eagle nests could occur. I have data about known ...
5
votes
1answer
8k 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 lenght(...
2
votes
1answer
127 views

How to make slope map from elevation map in Lat/Long?

I have an elevation raster map of the world, in Lat/Long. When I make a slope map, the results of the raster cells will be either 0, or values close to 90. The problem seems to be that the Slope ...
1
vote
1answer
798 views

Buffer analysis - use of surface area based on DEM

I have one problem and this is that I would like to create a buffer around point. This is simple with ArcMap using the buffer tool. But is it possible to create the buffer considering also the true ...
1
vote
0answers
184 views

Performing Theil-Sen regression on raster data by R software

I have seven NDVI raster layers (in ERDAS img format) of an area. Each NDVI layer is the peak growing time of that year. I want to do trend analysis of NDVI values change over the years pixel by pixel....
0
votes
1answer
463 views

Determine start/end points for line slope calculation [duplicate]

This is a follow up question based off of this question. I have a line feature class representing storm drains and a point feature class representing where storm drains are connected. The point ...
0
votes
0answers
214 views

QGIS: calculate slope of line-segments

Using QGIS, I'd like to achieve the same as in question calculate-slope-of-street-segments. I have a shapefile with lines (rivers) and a DEM. So I suppose the best way is somehow like this: 1 - ...
1
vote
1answer
161 views

Calculate slope of line based off of point layer

I have a line feature class that needs to have its slope included as a field. I have a point layer that contains points and their elevations for the start and end of the line segments. How can I ...
2
votes
1answer
113 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 ...
0
votes
0answers
92 views

Problem with calculating slope in QGIS

Ive downloaded DEM form earthexplorer. But after calculating slope I only have blac img. with same value in min. and max. When calculating aspect or relief, DEM works correctly. Have you met with ...
2
votes
1answer
615 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 ...
1
vote
1answer
62 views

Mean watershed slope - are there better methods than taking the mean of the contained slopes?

I am wondering if there are better methods for determining the mean watershed slope, other than taking the mean of the slope values contained within the watershed? For example, could or should one ...
0
votes
0answers
28 views

Another Z-Factor Challenge

I've been working on a DEM, trying to calculate the slope. I have it in WGS_1984 and re-projected into NAD_1983_MTM_8, my preferred projection for this project. Every time I run the slope tool, ...
0
votes
0answers
92 views

Problem in running r.slope.aspect in GRASS

I am new to GRASS GIS, and have been trying to use the r.slope.aspect function to find out the slope, dx and dy rater map from an elevation map(512*512)[1]. But I am getting the following output: ||...
1
vote
1answer
134 views

How to perform slope using PostGIS?

I want to perfom Slope using PostGIS. I used this query but i got a strange result unit : create table my_slope as SELECT ST_Slope(rast,1,'32BF','PERCENT',1, false) as slope FROM my_raster I wonder ...
0
votes
0answers
64 views

How to make a map showing the slopes of the terrain

I am not too familiar with techniques, and was looking for ways to make a slope map for a given area. It ended with finding this site and posting the question. We are in the process of zoning a new ...
2
votes
1answer
655 views

Hydrology tool dataset in ArcGIS 10.1 for calculating slope?

I am quite new to the hydrology toolset in ArcGIS and thought it may be useful for extracting slope data from a raster. I was wondering if anyone had experience trying to extract slope data upslope ...