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Mar
2
answered Is WGS 84 datum, coordinate reference system, or both?
Mar
1
comment Remove certain polygon from SpatialPolygonDataFrame
Be wary of "AREA" attributes. There's no guarantee that's the actual area, right? You can use rgeos::gArea(x, byid = TRUE) to calculate it, and rgdal::spTransform if you need to change projection for that calculation.
Mar
1
comment What does ArcGIS have that QGIS doesn't?
Spacedman way ahead . . .
Feb
29
comment Elevation profile of river in R
Yes, extract will pull out every pixel crossed by Lines.
Feb
27
revised SpatialPointsDataFrame too slow FOR LOOP
added 191 characters in body
Feb
27
comment SpatialPointsDataFrame too slow FOR LOOP
Another option is to use readOGR() with the MSSQLSpatial driver.
Feb
27
comment SpatialPointsDataFrame too slow FOR LOOP
Looks like you are right, did not expect that. Use WKB and wkb::readWKB instead. Text is inefficient.
Feb
27
comment SpatialPointsDataFrame too slow FOR LOOP
I think we need to explore the SQL Server doc. What version etc. Probably another question :)
Feb
27
revised SpatialPointsDataFrame too slow FOR LOOP
added 43 characters in body
Feb
27
answered SpatialPointsDataFrame too slow FOR LOOP
Feb
27
comment SpatialPointsDataFrame too slow FOR LOOP
Given that these are just points, why are you using a Geometry type? Why not just get X/Y or long/lat from the query?
Feb
27
comment Read SQL Server Geometry datatype in R
Cripes, sorry - readWKT is not vectorized. I don't know why that is. I'll see if can be. There'll be a much faster way to do it, and via WKB would be much better.
Feb
27
comment Read SQL Server Geometry datatype in R
readWKT is vectorized, there's no need to loop - and especially not by "growing" the object incrementally - that is hopelessly inefficient. If you have another question, don't post it in comments, but probably all you need is to remove the index: SpatialPointsDataFrame(readWKT(df$WKT),data=data.frame(OBJECTID=df$OBJECTID, LOT_NO=df$LOT_NO)) - might need to handle the rownames too.
Feb
27
answered Read SQL Server Geometry datatype in R
Feb
26
comment Understanding difference between Coordinate System and Projection?
Area and distance can only be sensibly calculated in a projection if/where the projection properties support it. They rarely do for distance, and often don't for area.
Feb
26
comment Understanding difference between Coordinate System and Projection?
WGS84 is not a cs, it's a datum. Loose terminology is rife here.
Feb
22
comment Index TAB for large raster files
And see for a possible alternative gdal.org/gdaltindex.html
Feb
22
comment Index TAB for large raster files
Gosh, blast from the past I forgot about these. Pretty sure those .tabs are text, have a look with a good text editor. Very easy to program their creation if you need
Feb
19
comment How to correctly rasterize a polygon which crosses 180E longitude?
Use a projection that makes sense for your domain, longlat is a weird non-projection and rarely has sensible properties for any application.
Feb
15
answered GRIB to NetCDF with GDAL, specifying dimensions