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I tried to "parallelize" the function rasterize using the R package parallel in this way: split the SpatialPolygonsDataFrame object in n parts rasterize every part separately merge all the parts into one raster In my computer, the parallelized rasterize function took 2.75 times less than the no-parallelized rasterize function. Note: the code below ...


4

Yes, GRASS GIS can be used in parallel mode. I would suggest that you review the detailed GRASS Wiki page on Parallel GRASS Job as well as the discussion on OpenMP. There is also some interesting reading (and further links) on parallel grass jobs here.


3

Trying to put it really simply, the way I see it is this. If I go out with my compass (or gps, or some other kind of navigation tool) and head north I will eventually get to a point where I can't head north anymore. But if I go out with my compass and head east I will never get to a point where I can't head east, I can just keep going. If I head North, from ...


3

The meridians correspond to the natural fact that the sun reaches the zenith once a day simultaneously for a set of points that form a straight line from one pole to the other, cutting the equator in a right angle. So meridians are not just artificial lines, but correspond somehow to a natural aspect, something that can be measured. Even with your bare eye, ...


3

i would add a intersects join clause on this query like this DROP TABLE IF EXISTS schema.zonal_stats; CREATE TABLE schema.zonal_stats AS SELECT id,geom, (ST_SummaryStats(ST_Union(ST_Clip(raster,geom)))).sum FROM schema.raster join schema.ply on st_intersects(raster,geom) GROUP BY id,geom; this will run more efficiently because it will use an index and ...


3

The problem you are experiencing is actually twofold. Firstly, and as pointed out by @EdzerPebesma, you are not loading the required packages on each of the 4 nodes separately. You have to use clusterEvalQ to tell each node which packages it is going to need to fulfill the required (spatial) tasks. Secondly, you need to assign a proj4string to the polygon ...


3

I think the most likely reason for the different behavior is related to when and how the data is accessed. In the case of the TIF, there is essentially a TIF-access pointer that is being shared between processes/threads. The reading of information from thread A interferes with thread B that is also trying to read data using the same in-memory interface. ...


3

If you are trying to extend your parallel line while keeping its orientation (angle), please try following steps. Before this, you need to make sure "Advanced Digitizing Panel" is displayed by View | Panels |(check) Advanced digitizing panel. Then Toggle Editing on your line layer Add Feature Enable advanced digitizing tools Click your first point Click ...


2

You can use QAD plugin which acts as AutoCAD, and there is an offset tool to that you can use to create parallel line at specified distance. You have to make sure that the tool works only on projected coordinate system not geographic coordinate system, so you need to project your data to before using it, and do not forget to start the editing mode. This a ...


1

This doesn't answer the question 100% but does answer my problem, which is to speed up zonal statistics. I am using the following exactextract command line tool for fast zonal statistics. This also takes into account partial overlaps, by weighting the zonal statistic for each raster value by its coverage fraction. Many zonal statistic tools do not account ...


1

You need to export the dates variable as well because it is a global beginCluster() z1 <- clusterR(ndvi, calc, args=list(fun=f), export=c('a','dates')) endCluster() or c1 <- getCluster() clusterExport(c1, c("a","dates")) z2 <- calc(ndvi, fun=function(x){ t(parApply(c1, x, 1, f))} )


1

"filelocation is of the same length as glaciers" and in the same order? In which case: for(i in 1:length(filelocations)){ r = raster(filelocations[i]) # get the ith file name g = glaciers[i,] # get the i'th row of `glaciers`. r = crop(r, g) # crop writeRaster(r, file.path(outputdest, filenames[i])) # save in outputdest }


1

Zoom to your polygons extent. Use Processing - QGIS geoalgorithm - Vector Creation Tool - Create Grid to make a line grid at the same processing extent at the current window at your spacing preference. Manual delete the horizontal or vertical lines and save your edits. Use Use Processing - QGIS geoalgorithm - Vector Overlay Tools - Clip to clip the ...


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