Questions tagged [saga]

SAGA (System for Automated Geoscientific Analyses) is a GIS toolbox with many modules that can be used from the GUI, command line or accessed through R,python or directly using C++.

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41
votes
4answers
2k views

Generating equal sized polygons along line with PyQGIS?

I would like to create polygons along a line to use them for AtlasCreator in a next step. ArcMap has a tool called Strip Map Index Features. With this tool I can choose the height and width of my ...
32
votes
5answers
56k views

Splitting shapefile into separate files for each feature using QGIS/GDAL/SAGA?

I have a polyline shapefile with about 20 kinds of roads. I would like to know how can I create automatically a vector file for each one. I am aware of how to do it using ArcGIS for Desktop - see ...
28
votes
7answers
29k views

How to set all pixels with value <= 0 to “nodata” in DEM raster?

I have a DEM raster with pixel values between about 3000 and -0.0003. I need to set all pixel with a value of 0 and smaler (<=0) to "nodata" (for later raster calculations and to reduce the ...
18
votes
1answer
569 views

Determining flow path length in QGIS?

I need help with qgis flow path length. I try to run the program and when I run the program I get a raster with 0 values, as input I'm using filled raster, I don't now if I'm doing something wrong or ...
16
votes
4answers
5k views

Manually correcting raster DEM (OpenSource)?

Is it possible, to correct a raster DEM by changeing the raster-cell-values manually, like by "painting"? My DEM (ASTER) have one small error where the elevation is about 300m below the actual ...
15
votes
5answers
14k views

How to split a vector into equal smaller parts in QGIS or similar?

i want to divide a shapefile with many tiles into a lot of smaller tiles. I am searching for a smart solution, because manual edits are out of questions Anyone can help or know a nice function?
14
votes
5answers
24k views

How to calculate raster statistics for polygons?

how can I calculate sums, averages etc of raster-points (multi-band) per polygon of a vector-layer. I was told that this is called "zonal statistics". I tried that with QGIS first. There is a way to ...
13
votes
1answer
3k views

Import GRASS and SAGA modules to python script

I'm new at this. I am "building" a python plugin for qgis and I want to import modules from GRASS and SAGA but I don't understand how to do it. The plugin I want to import is Kriging interpolation ...
13
votes
1answer
696 views

Irradiance analysis - GRASS vs SAGA significant discrepancies

I wanted to calculate and visualize the irradiance values for a plot. Do not know why, but in my copy of QGIS 2.18.5 I am missing appropriate SAGA module in the "Terrain Analysis -> Lightning", so I ...
12
votes
2answers
5k views

How to smooth large vector polygons from Raster

I have a landuse classification raster file (6 classes) of a large area. But I need it in vector polygons so I vectorised it. No problem so far, but the result is - of course - that every pixel is ...
11
votes
2answers
3k views

How to implement viewshed calculation?

I'm looking for a way to implement visibility (aka viewshed). I found a previous GIS SE question that suggested a few GIS applications (not what I need - I'm trying to embed the calculations), and ...
10
votes
5answers
5k views

How to generalize and vectorize a LandUseClassification raster file?

I want to vectorize that rasterfile with its 6 landuse classes. The classification is very noisy and have to be generalized before. The result should be a polygone vector file. I use SAGA, (GRASS) ...
10
votes
2answers
3k views

What is the source of horizontal and vertical striping in USGS DEMs?

When processing 30m and 10m DEM data downloaded through the National Map Viewer from the National Elevation Dataset, we noticed horizontal and vertical striping not only in the produced results, but ...
10
votes
2answers
9k views

How to compare two DEMs and show their difference?

I want to compare my DEMs with each other (ASTER GDEM2 and SRTM4.1). I know, that the GDEM has some "holes" with wrong elevations (I found 3 of them in my working area). Now I need to know, if there ...
10
votes
4answers
2k views

How to automatically plot intermediate contours with QGIS, GRASS GIS or SAGA GIS?

I'm mapping a steep mountain range. My main contour interval is 50 m and my intermediate contour interval is 10 m. In steep areas, the interval of 10 m is too small, so I need to leave ...
10
votes
2answers
9k views

How does Zonal Statistics work exactly?

I'm a bit confused on how the zonal statistics tools work in QGIS (either the 'Zonal Statistics' tool under the Raster tools from the QGIS geoalgorithms toolbox or the 'Raster statistics from polygons'...
10
votes
1answer
748 views

SAGA Inverse Distance Weighting in QGIS - How to Set Minimum Number of Points?

I am analyzing a postGIS point dataset in QGIS version 2.8.2, about 200k features total. To calculate weighted average values I am using the Inverse Distance Weighted interpolation technique. However, ...
9
votes
1answer
562 views

Which SAGA versions does QGIS 2.18.10 support?

Beginning with QGIS 2.18.10 the SagaAlgorithmProvider do not longer have a dictionary called supportedVersions. Previously, it looked like this: supportedVersions = {"2.1.2": ("2.1.2", ...
9
votes
1answer
16k 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 specific catchment area (a=A/L, catchment area (A)divided by contour length(...
9
votes
1answer
467 views

QGIS 3 and SAGA 3.0+ Integration

I've looked all over the net and I'm wondering if there are any plans by the QGIS developers to integrate some of the newer versions of SAGA available in the repository and as binaries on the project'...
8
votes
2answers
2k views

Seeking open source alternative to ArcGIS Desktop's Integrate tool?

I need to snap about 1000 lines in one layer to the lines in another layer (there are about 5000 lines in the second layer). The lines to be snapped are about 15 map units away from the base layer ...
8
votes
7answers
2k views

How to integrate SAGA Python Modules into ArcGIS Desktop?

I have been having a look at SAGA (http://www.saga-gis.org/en/index.html) and it seems to have some nice tools for geoprocessing. I was wondering if anyone out there has had any luck bringing SAGA ...
8
votes
4answers
3k views

How to change SAGA path in QGIS 2.18 Standalone

I have installed QGIS 2.18 Standalone (64 Bit) with SAGA GIS (2.1.2) and GRASS GIS 7. Afterwards I have installed the newest SAGA GIS 3.0.0. I want to change the SAGA folder in the processing options,...
8
votes
2answers
2k views

SAGA algorithms not working on Qgis 2.18 on Mac OSX

Since last update to Qgis 2.18 from 2.14, I'm unable to successfully run SAGA algorithms (Mac OSX Yosemite). No matters if it is vector- or raster-oriented algorithm, the algorithm stops at this point ...
8
votes
1answer
986 views

Where is this raster offset being introduced in the QGIS processing toolbox?

I'm using the (awesome!) processing toolbox in QGIS 2.0 to reclassify some NoData values in a raster from -9999 to 0, but at some point in the process there's an offset of about 0.2 degrees being ...
7
votes
6answers
2k views

Tool/Algorithm for generalizing OSM-Files for printing maps

Is there a tool or algorithm to (topological) generalizes OSM-shapes? I would like to build a printable map in different scales. In the image below you can see the same divided road (yellow) at ...
7
votes
3answers
6k views

How to configure QGIS and SAGA on Ubuntu (12.04 and others)?

During the past weeks, I have tried QGIS to recognize SAGA via the processing toolbox, both being installed from the ubuntugis-unstable repository. I have tried this on several virtual ubuntu ...
7
votes
2answers
2k views

How to de-noise a DSM?

I have created a DEM, DSM, and nDSM from a LiDAR Point Cloud using SAGA-GIS. I extracted the appropriate returns from the point cloud, then converted to grid, and then closed gaps to fill in any ...
7
votes
2answers
187 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. ...
7
votes
1answer
8k views

Installing SAGA GIS 2.1

I am using QGIS 1.9 master with Ubuntu 13.04. I tried to use the SAGA hydrology tools in sextante today and it said they did not appeared to be installed. I checked and sure enough SAGA was indeed ...
7
votes
1answer
7k views

Calculate Topographic wetness index in SAGA

i am currently working on a project which involves the quantification of the wetness in certain areas. However it produces quite different results from what i expected. I'll describe the steps i have ...
7
votes
1answer
2k views

Is there any way to include “universal” style/symbology in GeoPackage?

I am just playing with the GeoPackage format in QGIS. In QGIS it works nice with the style saved from QGIS but if I load it for example in SAGA the style is not applied. Is there any way to include ...
7
votes
3answers
484 views

Using variable window (“kernel”) size for raster processing in QGIS?

I'd like to use differently sized windows as I process (a.k.a. filter) a raster, with the size varying according to latitude. There are tools that allow a user to specify custom windows (e.g., "User-...
7
votes
2answers
266 views

Improve DTM under forested areas without smoothing?

I'm using a DTM retrieved from LiDAR data and I noticed that forested areas are grainy or not defined. The DTM data was retrieved from geostore.com. Here is one example: Is there any way to directly ...
7
votes
1answer
297 views

Why is SAGA kriging slower in QGIS than in SAGA itself?

I'm using QGIS for a while. In my opinion the SAGA kriging tool (processing toolbox) is very slow. Is that an QGIS issue? I tried to interpolate a point layer with 300.000 points (I know it is big) ...
6
votes
3answers
2k views

LiDAR data density, returns per square meter

How can I compute a raster showing the number of return points per square meter using SAGA GIS or other open source software? My goal is to obtain a mask which would show me the places (cells) ...
6
votes
1answer
765 views

Strange output from RSAGA topographic wetness index? [duplicate]

I am trying to generate a topographic wetness index raster with the RSAGA package in R. The output I am able to generate does not make sense to me, as it has a large number of NA cells and I wonder if ...
6
votes
1answer
2k views

Interactively determining upslope and downslope areas on DEM?

I know SAGA GIS can be used to interactively generate maps of upslope and downslope areas for a cell within a DEM, but the output is pretty ugly. An upslope area is defined as all cells (for a ...
6
votes
2answers
3k views

Installing qgis 2.0 and saga 2.1 on ubuntu 13.04

I have been trying to get this working for a few weeks now. I am trying to install QGIS Dufor (2.0.1) and Saga GIS from the Unstable branch of the UbuntuGIS PPA. When I attempt to do this I get the ...
6
votes
2answers
1k views

Estimation of volume from DTM

I'm using QGIS for quite a while now but I'm having some problems in measuring the volume of a depression zoned North of a waste dump I'm studying. For the analysis I'm using a recent 1mx1m DTM of ...
6
votes
1answer
749 views

SAGA GIS raster calculator - QGIS scripting gt expression

I am trying to perform a simple raster calculator that takes input rasters and outputs a new raster with a constant value where values exceed a specified number in the input. This is part of of a ...
6
votes
1answer
441 views

Stripes in Landsat-image after topographic correction (SAGA)

I got stripes in my topographic corrected Landsat images (see second image below). I used SAGA GIS 2.0.8 at xubuntu 12.04 Image and DEM are in the same projection, tried it with EPSG:32636 and EPSG:...
6
votes
1answer
5k views

Performing Ordinary Kriging in SAGA via QGIS SEXTANTE Plug-in?

I'm trying to learn how to apply the kriging analysis in QGIS using the SEXTANTE plug-in and SAGA tools. It appears that I have my SEXTANTE and SAGA folders configured properly according to the user ...
6
votes
3answers
1k views

Create a rectangular buffer from point shapefile using QGIS/GRASS/SAGA GIS/R

I have a points shapefile and I want to create a rectangular buffer (22 x 16 km) around each point. My goal is to create a 16x22 km grid where each of the points is the centroid of the grid. Seed the ...
6
votes
2answers
7k views

How to install SAGA 2.1 with QGIS dufour on Windows?

I need that someone tell me how i can install saga in qgis 2.0 correctly in windows, because if I install QGIS 2.0 and when I try to use SAGA I get this Missing dependency.This algorithm cannot be ...
6
votes
1answer
5k views

Unsupervised classification in QGIS

I was trying to learn unsupervised classification in QGIS 2.6 following the tutorial video: https://www.youtube.com/watch?v=mI80eENtWSE When trying myself, clicked Run during the process it shows the ...
6
votes
1answer
4k views

How to configure QGIS Sextante to use SAGA?

I have been trying to set up SAGA to work using Sextante in QGIS. I have followed the instructions to configure SAGA in Sextante, with the following input in the path for the SAGA folder C:\Program ...
6
votes
1answer
193 views

Rename outputs from QGIS processing saga algorithms

I have a processing script which chains together several saga processing tools like this: outputs_SAGARASTERCALCULATOR_3=processing.runalg('saga:rastercalculator', inputvx,[inputvy],'(atan2(a,b)) * (...
6
votes
1answer
781 views

Flow Path length

I'm a student and pretty much new to QGIS, GRASS and SAGA tools. I'm trying to calculate the longest flow path length using SAGA "flow path length" module in Qgis. Using the default parameters: I'...
6
votes
1answer
2k views

Joining 2D polylines and DEM into 3D polylines using QGIS/GRASS/SAGA?

I have a road network in 2D/PostGIS and a DEM. I want to turn the road network into 3D by retrieving the Z-value from the DEM. Both files are quiet large so an efficient process is needed. I'd prefer ...