[GIS] Rasterize a vector layer in PostGIS

postgisraster

Related to this question asked here on gis.se and this thread on postgis-user, has anyone worked out a good solution for in-database rasterization of a vector layer using PostGIS? It sounds like the necessary functions are available and it is possible to get a valid output, but not one that is readable by GDAL et al. because it has irregular tiles.

To be more specific, I would like to rasterize two distinct vector maps of the US, counties and NBCD mapping zones, to a particular resolution and both aligned with an existing raster. It is possible to do this with gdal_rasterize, but with some trial and error as I recall — mainly because the extents of the three inputs do not match, I expect.

Any thoughts?

Best Answer

Here is a guide on how to rasterize a vector table in PostGIS...

Related Solutions

R Vector to Raster – How to Rasterize a Vector Dataset in R

Here's a suggestion:

# Use rgdal, better library
library(rgdal)
coastline <- readOGR(dsn=".", layer="coastline")
wets <- readOGR(dsn=".", layer="wets")

Rasterize 'em:

require(raster)
# Create a generic raster, set the extent to the same as wetlands
r.raster <- raster()

Use extent (from raster package) to read bounds of vector and assign to the raster:

extent(r.raster) <- extent(wets)
res(r.raster) <- 2500 # set cell size to 2500 metres

# Make a raster of the wetlands:
coastline.r <- rasterize(wets, r.raster)

# Do the same buffering operation but in raster:
wetb <- buffer(wets, width=500)

If you want to do it by individual features, you could loop through them and create a raster stack layer for each feature.

[GIS] Converting a PostGIS raster back to vector

You would use something like:

-- Dump As Polygons -- http://postgis.net/docs/RT_ST_DumpAsPolygons.html

-- ST_Polygon -- http://postgis.net/docs/RT_ST_Polygon.html

To convert your your raster back to a geometry. Except note that since rasters are tiny pixels, you get back an areal geometry.

In PostGIS 2.2.0 -- release is eminent, if you have built with SFCGAL, you can use

the ST_ApprovimateMedialAxis.html

http://postgis.net/docs/manual-dev/ST_ApproximateMedialAxis.html

the ST_StraightSkeleton function,

http://postgis.net/docs/manual-dev/ST_StraightSkeleton.html

I think ST_ApprovimateMedialAxis.html does close to what you want when applied to the polygon you get back from raster. I think others have plpgsql functions lying around that do something similar too if you can't get your hands on SFCGAL enriched PostGIS 2.2

Best Answer

Related Solutions

R Vector to Raster – How to Rasterize a Vector Dataset in R

[GIS] Converting a PostGIS raster back to vector

Related Question