1,824 reputation
713
bio website staff.acecrc.org.au/~mdsumner
location
age
visits member for 3 years, 5 months
seen 18 hours ago

R, Manifold, GDAL, also interested in Python, topojson/D3 and NetCDF/HDF


2d
comment RasterStack extract() for duplicated dates
just use sub <- subset(temp, 18263:23011) and then (admittedly I don't know what should happen here, sp can be overly prescriptive) use your second line as you did. I suspect your -99 thing is due to a problem with the coordinates themselves, but you don't provide enough info here.
2d
comment RasterStack extract() for duplicated dates
What is temp@layers? You should not be using the @ operator btw, where did this code come from?
Apr
14
comment How do I peform a true GIS Clip of polygons layer using a polygon layer in R
Try gIntersection with byid=TRUE (I think it's a problem with dangling topologies for certain clips, and sometimes doing it this way helps), for speed check out gUnarySTRtreeQuery() or gBinarySTRtreeQuery() to identify intersecting bounding boxes of pairs of polygons and only intersect those pairs. There's no easy high-level wrappers for all of this afaik
Apr
14
comment Mapnik: GeoTIFF flipped (mirrored vertically)
I would figure out why it's coming out positive from QGIS, it can be tricky to track down where the interpretations are applied in a workflow like this, we need a reproducible example
Apr
11
comment Mapnik: GeoTIFF flipped (mirrored vertically)
Y pixel size would usually be negative in test.tif, not all tools will apply the transform correctly without that.
Apr
8
comment Extract Raster from Raster using Polygon shapefile in R
Use projectExtent() to get just the extent for cropping the raster.
Apr
8
comment Extract Raster from Raster using Polygon shapefile in R
extract() does perform on the fly reprojection, but crop() does not. That might account for some confusion
Mar
26
comment How to create a time series with a NetCDF raster from Ensembles E-OBS using GDAL, R, GRASS GIS or SAGA GIS
In R, start with library(raster);(ncdata <- brick("file.nc")) and report back on what you get. You'll need either ncdf4 or ncdf packages also installed for raster to use.
Mar
24
comment What programs would allow for the mapping of a geoid in 3d?
R's rgl could do this, can you add a link to the data and I will have a go.
Mar
23
comment Is it possible to render tile-based web mapping projects in any other projection than web mercator?
Yes of course it's possible, just use gdal2tiles it's really easy. Interoperability, not sure, but I don't see that it's really relevant. Mercator is a terrible projection, it's just a simple compromise for the entire globe in one plane. There's also longlat, Cylindrical Equal Area, Peters, and none are "very good" because they apply to the whole world, but they work in a narrow context for a purpose.
Mar
15
comment Making a georeferenced PDF or GeoTIFF from jpg+jgw using GDAL for Avenza PDF Maps
We can only guess at the problem with the information you have here
Mar
15
comment Making a georeferenced PDF or GeoTIFF from jpg+jgw using GDAL for Avenza PDF Maps
You can't, TFW is just the 6 figure affine transform. That is why you should use good feature-rich formats, not these ancient legacy hacks. We all need to demand better
Mar
10
comment Problem with MIF/MID allignment
"Some other software" is not descriptive enough for this site. You should describe exactly what you are using and the steps used.
Mar
10
comment I want to reproject data from 0-360 to -180 - 180
You can create a VRT data set to do the job: trac.osgeo.org/gdal/wiki/UserDocs/RasterProcTutorial
Mar
8
comment Making a georeferenced PDF or GeoTIFF from jpg+jgw using GDAL for Avenza PDF Maps
You at least need to add the coordinate system with -a_srs maybe that will help Avensa? Can you include the output of gdalinfo for each stage?
Mar
8
comment Per-pixel calculations on a raster stack using GDAL
I will when you add sufficient detail about what you are doing and how. :)
Mar
8
comment Raster: mosaic first, or project first?
I don't the second option makes any sense, there will be edges broken everywhere. Option 3 is just a way of achieving 1. Do a test with 3 and then commit that VRT to a tiled and compressed GeoTIFF if the performance is too slow.
Mar
8
comment Per-pixel calculations on a raster stack using GDAL
It might be worth looking closer to find a faster way in R/raster, there are a few ways to do it and the details matter. Happy to do that perhaps outside this q if you want
Mar
6
comment How can I correct a .pgw file for a PNG image?
There's obviously no coordinate system metadata so I would check that the right one is assigned or in-use when you load it. It is probably being displayed with an assumed projection that is wrong. (Best to use a spatial format like GeoTIFF that can store all this stuff but hardly anyone does unfortunately)
Mar
6
comment gdal2tiles generates small picture inside 256x256 tile
This works if I do this, with no -z argument: python gdal2tiles.py -p raster ibcso_background_hq. tif ibcsoraster I can maybe have a closer look later, but it might be something to do with how the levels interact, but otherwise def a bug in the script.