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1

I had a similar problem. PostGIS wanted libgdal1 and QGIS wanted libgdal1h. The problem was that I had my Repo for QGIS set to the main QGIS site, and Postgresql set to their main site. Postgresql kept wanting to upgrade past what QGIS wanted. Finally something gave and I ended up with circular conflicts between the two. I ended up backing up my ...


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Your question is two-fold. With regards to the actual atmospherically corrected data: there is no simple method for testing if the calculated reflectance values are right. However, the simplest approach is to compare the resulting spectras to known spectras from the literature. Which bit of literature you need to find depends on your area / local ecosystem ...


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You find an explanation of FCELL, DCELL and CELL in the introduction to 2D raster maps: http://grass.osgeo.org/grass70/manuals/rasterintro.html Data type CELL represents integer data values, FCELL single-points floating values and DCELL double-precision floating point values.


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This is how you can do this with R: library(raster) r <- raster('your file name') tab <- cbind(0:9 * 1000, c(1:9,Inf)*1000, 1:10) x <- reclassify(r, tab, filename='output.tif', datatype='INT2S')


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You can use the QGIS plugin LRS for that. It accepts points not lying on the line, so you avoid the first step (snapping points to lines). This is the workflow: Based on both a line (routes) and a point (for calibration) layer, go to the Calibration tab. Select the line (pipeline) layer with its route field (a field that identifies routes, it's very ...


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If you're wanting to use GRASS within QGIS, you can use GRASS tools from the QGIS Processing Toolbox which contains tools from QGIS, GRASS and many others: Make sure the folder paths are correct for each provider via Processing > Options and configuration > Providers


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Re-run the setup, change to advanced install and look if the package grass is selected. It should be selected automatically as dependency. If it is, look under Processing -> Options -> Dataproviders -> GRASS commands. The first item should be checked. Finally, make sure to switch to advanced interface at the bottom of the processing toolbox. You ...


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I'm also on OSX Yosemite using QGIS and GRASS, the GRASS shell in QGIS doesn't start, but it's hard to use anyways (It's hard to copy-paste, the font is hard to read and there is no cursor or command history). I start GRASS in the OSX Terminal, doing all analysis there, while I use GRASS in QGIS to export shapefiles into the GRASS database, and to load them ...


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Yes same problem here. What I did to speed up this process was to load SHP files in PostgreSQL and do clipping there. Not a perfect solution but faster for me since I quite powerful server behind it. And yes, this operations are slow. I hope this improves in the future.


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There is a related button in the startup screen (lower right): http://grasswiki.osgeo.org/wiki/File:Wxgui-startup-gnulinux.png which allows you to delete a location. Or simply delete the location directory like any other directory on your computer.


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The following solution is feasible only if you have a limited, manageable number of large polygons. First save each polygon as a separate, single-feature shapefile. Then for each one, do the following. My method is to use the MMQGIS plugin to export the feature set as .csv nodes, then open the .csv in a spreadsheet, and do a custom filter for shape_id cells ...


2

Sympy is inappropriate here (or very difficult to use). For geometrical calculations in 2D, the best solution is Shapely. But don't forget that GRASS GIS 6.4.x has the module grass.script (look at GRASS Geoprocessing in Python Script) and GRASS GIS 7.x, the new module pygrass. You can also use the general Python modules GDAL/OGR (osgeo) or Fiona to open ...


1

What you refer to as half basins are often called hillslopes. I'm not aware of any tool in GRASS GIS that can extract these features from a stream network and a DEM, although it is possible that I have overlooked the correct tool. However, if you are open to using alternative open-source GIS then I can recommend the hillslopes tool in Whitebox GAT, for which ...


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Micha, That's exactly how I've proceeded and I've still met the same walls that Knives met. So frustrating!


2

The problem might be with your rule file. When you use GRASS through QGIS, it will do something similar: Gather input parameters from you with a dialog box. Initialize a command line GRASS instance. Import the input file in a temporary GRASS location. Execute a script with your parameters. Export the result. Draw the result on canvas (if specified). In ...


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again, I found the answer somewhere else: http://lists.osgeo.org/pipermail/grass-user/2010-October/058381.html "The base map should be integer (category ) values, where the mode is calculated for all cells with the same cat value, so it indeed should be an integer raster." I need to transform my float values into integers, but before I need to multiply ...


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I ended up working through QGIS. Grass itself is quite overwhelming. Still having basic issues with projections, getting a hang of the data structure and executing r.walk. Thanks all.


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Examining the content of the file .../.qgis2/processing/processing.log after running the processing toolbox command gives you the result: ALGORITHM|Fri Jan 09 2015 18:18:40|processing.runalg("grass:r.mapcalculator","/Users/mytiff.tiff",None,None,None,None,None,"round(A)","202086.577,205625.414407,88411.048,90534.3504441",0,"/Users/mytiffr.tiff") And if ...


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The following QGIS Raster Calculator expression should be sufficient (raster layer named "myraster"), since the QGIS Raster Calculator sets all pixels that do not satisfy the condition to nodata: ("myraster@1" > 0) * "myraster@1"


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There is a helper script as well in the code: http://trac.osgeo.org/grass/browser/grass/trunk/imagery/i.atcorr/create_iwave.py It generates the filter function IWave.cpp template from the csv file.


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Thank you Nikos and Markus for the comments. Using Nikos' hpf module I get a nice pansharpened image. The steps taken to do this (also in i.fusion.hpf documentation): Download the module from github, open Grass 7.x.x In the Grass command console (bottom of the layer manager window, second tab from the left), navigate to the directory where you extracted ...


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You mentioned that your point text file was created with v.out.ascii. That module adds a third column with the cat value. So you'll have to add to your "while read" loop like so (even though you don't need the cat value): while read X Y cat; do....


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For some basic tutorials and exercises for GRASS, you can check this link which I think is a great place for beginners. There are also a couple of other sources which describe the r.walk and r.cost functions and their associated parameters in greater detail (although I'm assuming you have already read these).


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There is a QGIS tool which is designed to help remove sliver polygons: Vector > Geoprocessing Tools > Eliminate Sliver Polygons An alternative method which may or may not work (depending on your polygons and attributes) is to use the Dissolve function (Vector > Geoprocessing Tools > Dissolve) and select a unique attribute column for the dissolve field. I ...



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