Questions related to slope analysis.

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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 ...
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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?
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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 ...
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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 ...
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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 ...
3
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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 &...
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0answers
37 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
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2answers
137 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 ...
2
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1answer
166 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 ...
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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....
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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 ...
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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 ...
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1answer
144 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 ...
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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.
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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, ...
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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 ...
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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 ...
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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 ...
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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> ...
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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 ...
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1answer
113 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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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....
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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 ...
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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 - ...
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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
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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 ...
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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 ...
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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 ...
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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, ...
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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 ...
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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: ||...
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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 ...
1
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1answer
82 views

Why slope tiff image produced with QGIS does not show properly in paint?

So I have this slope tiff image that I created using a DEM reprojected in meters. When I view it in QGIS, it shows fine. If I try to edit the picture in paint or Gimp afterwards, I dont see the same ...
4
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1answer
207 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 ...
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2answers
804 views

How to properly get the slope from an ASTER DEM in QGIS?

I have inserter a raster dem layer from ASTER satellite and I want to get a raster that has the slope of the area. I use terrain analysis > slope but the output is so wrong. Why is that? here is the ...
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0answers
39 views

How do I make a constant slope elevation model in arcMap? [duplicate]

I am currently working with ArcMap to develop an elevation model of a quarry showing how the terrain at the quarry site would look post-closure. One of the requirements is that the slopes placed along ...
2
votes
2answers
276 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 ...
4
votes
1answer
834 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 ...
6
votes
1answer
126 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 ...
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2answers
224 views

Range of values in slope and aspect changes when I try to unproject my projected rasters

I use the SRTM DEM and I have used the "Project Rater" tool in ArcGIS10.2 in order to project it from GCS_WGS_84 to a certain UTM zone in WGS84. With my projected elevation raster, I have calculated ...
2
votes
1answer
246 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 ...
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0answers
20 views

Creating a new surface for a track layout with defined gradient of slope

I am trying to establish a way of creating a new raster surface for a new track layout. I have a section of track, and I have a DTM. I want to give my track section a height value and a width. However ...
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0answers
18 views

Calculating Slope, Flow Accumulation and Topographic Wetness Index (TWI) using ArcGIS for Desktop? [duplicate]

I am working on a project that requires me to extract values from rasters (viz the slope and TWI) for a set of point dataset that I have. I tried calculating the Slope, Flow accumulation and the TWI ...
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3answers
250 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 ...
2
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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 ...