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bio website staff.acecrc.org.au/~mdsumner
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R, Manifold, GDAL, also interested in Python, topojson/D3 and NetCDF/HDF


Nov
2
comment Prior art on rhumb line and great ellipse areas?
Equal area not angle. The extra vertices are not for calculating per se, just for representing the region in the right way. I don't get your overall task really, I don't see how it's any different to calculating area normally.
Nov
2
comment How to import NetCDF to PostGIS (or GeoTIFF)
And so for your question, the details matter! Please post a ncdump or gdalinfo (or equivalent) description of the file or variable within a file you wish to import.
Nov
2
comment How to import NetCDF to PostGIS (or GeoTIFF)
Is the problem you are having the import per se or different aspects of that import's interpretation? There's no end to the problems you can get when NetCDF meets GIS, the file spec is just so open it can completely depend on specifics for individual cases. So conversion to GeoTIFF simply puts the issue one step away without solving it.
Nov
2
comment Prior art on rhumb line and great ellipse areas?
Standard practice would be to do the calcs in an appropriately local equal area projection. Right? The only real issue is whether your shapes have sensible topology and/or sufficient vertices to represent whatever the thing is correctly when you transform, or draw it in that projection. (But this a constant concern that is basically a broken part of most/all GIS, and a key knowledge base item of the "expert-practitioner").
Nov
1
comment How convert a Modis hdf to txt with lat long using a command line
Use gdal_translate from an appropriate system build of GDAL. What is EVI?
Oct
28
comment Working with MODIS in R
Jeff: well only if rgdal has also been built with HDF.
Oct
27
comment las2dem issue - while generating a DEM raster cells with no data are being generated
Is this a licenced copy of lastools?
Oct
26
comment Unable to install ECW support on lubuntu 14.04
There's a stray space in the symbolic link step before "/libNCSEcw.so". I can't remove it because apparently fixing just one character is not allowed.
Oct
21
comment Definitive list of Proj4 supported coordinate systems
The command line options for "proj" -lp and -le and -ld list the available coordinate systems, ellipsoids and datums. It's not possible to list every possible combination of proj coordinate systems and all parameters (obviously) but those three lists give you a huge range of components to define what you need.
Oct
19
comment Converting LANDSAT-8 TIFF to matrix, data frame, or SpatialGridDataFrame formates
Read it it with the readGDAL function in the rgdal package, which returns a SpatialGridDataFrame.
Oct
17
comment Generic Grid to Coordinate System
Which manufacturer?
Oct
17
comment warping and outputting coordinates of GeoTiff data: advice and error checking
Warping inherently creates a new grid of points, it's got nothing to do with the original.
Oct
14
comment How to create a map colored by distance to nearest point in R
Would counties be small enough for your small areas to carry the message?
Oct
14
comment Convert PNG to GeoTiff using GDAL
Can you show us the image and tell the story of where it's from? I wrote this to R-Sig-Geo the other day for a similar problem: stat.ethz.ch/pipermail/r-sig-geo/2014-October/021814.html. Someone with the experience can help, but you'll need more information about where the image comes from and probably ultimately what it looks like.
Oct
14
comment Geometric Operations in GIS Systems
Short answer is just that it depends. Any "straight line" between two vertices will traverse a different line on the Earth depending on the projection. This is not going to affect operations that are relevant only to the vertices, but any time two segments (lines or polygon edges) cross then the interpretation will be different in different coordinate systems. There's no universal right answer, it depends on how the data is set up and what the intention of the operation is. There are many poor choices of projection, so choosing the right one is just as important as using one.
Oct
13
comment SQLite Driver available with R's rgdal:writeOGR?
I assume this is on Windows? Compiling rgdal is hard on Windows, and if it's not in the CRAN binary you are out of luck. It's relatively straightforward on Linux though, so perhaps rephrase your question if that's an option. Otherwise you might request that CRAN support SQLite on the win-build, though licensing terms may be a complication.
Oct
10
comment warping and outputting coordinates of GeoTiff data: advice and error checking
Warping a grid is not going to give lonlat points that correspond to the original pixels. Why not xyz out from the original and reproject those? Prob easy enough with command line tools but I usually do this in R so I need to try it first
Oct
7
answered gdalwarp leaves horizontal artifacts regridding from EASE-Grid (laea) to Polarstero (stere)
Sep
30
comment Google Earth / QGIS projection (great circle line)
You will need to segmentize (add vertices) in the original coord system. Maybe ge allows that option? You could do it in Qgis with an appropriate choice of Gnomonic but I would need to try that. Can you tell us the start and end longlat in WGS84?
Sep
30
comment Is there an image editor that can edit GeoTIFFs without affecting their embedded georeferencing?
Manifold is good but probably overkill and not free.