Mastering PostGIS

Raster import was covered in Chapter 1, Importing Spatial Data, subject and exporting is on its way in the next chapter, so we can look strictly into vector <-> raster conversion and processing.

For our use case, we will use EU-DEM dataset, produced using Copernicus data and information funded by European Union - EU-DEM layers. It's one arc second model of the whole European Union (without overseas territories). With its open license, we can use it with no concerns. The dataset is accessible by http://www.eea.europa.eu/data-and-maps/data/eu-dem.

As a vector layer, we can use OpenStretMap data for the Poland and Czech Republic administrative units.

In the first step, let's import the dataset as we learned in Chapter 1, Importing Spatial Data. For optimization of import processes, look into metadata, for SRID and size of raster, gdalinfo makes it easy:

user@machine:~/dev/gis/dem$ gdalinfo eudem_dem_5deg_n45e015.tif 
Driver: GTiff/GeoTIFF 
Files: eudem_dem_5deg_n45e015.tif 
Size is 18000, 18000 
Coordinate System is: 
GEOGCS["ETRS89", 
    DATUM["European_Terrestrial_Reference_System_1989", 
        SPHEROID["GRS 1980",6378137,298.2572221010042, 
            AUTHORITY["EPSG","7019"]], 
        AUTHORITY["EPSG","6258"]], 
    PRIMEM["Greenwich",0], 
    UNIT["degree",0.0174532925199433], 
    AUTHORITY["EPSG","4258"]] 
Origin = (15.000000000000000,50.000000000000000) 
Pixel Size = (0.000277777777778,-0.000277777777778) 
Metadata: 
  AREA_OR_POINT=Area 
Image Structure Metadata: 
  COMPRESSION=LZW 
  INTERLEAVE=BAND 
Corner Coordinates: 
Upper Left  (  15.0000000,  50.0000000) ( 15d 0' 0.00"E, 50d 0' 0.00"N) 
Lower Left  (  15.0000000,  45.0000000) ( 15d 0' 0.00"E, 45d 0' 0.00"N) 
Upper Right (  20.0000000,  50.0000000) ( 20d 0' 0.00"E, 50d 0' 0.00"N) 
Lower Right (  20.0000000,  45.0000000) ( 20d 0' 0.00"E, 45d 0' 0.00"N) 
Center      (  17.5000000,  47.5000000) ( 17d30' 0.00"E, 47d30' 0.00"N) 
Band 1 Block=18000x1 Type=Float32, ColorInterp=Gray 
  Min=54.810 Max=2424.210 
  Minimum=54.810, Maximum=2424.210, Mean=317.651, StdDev=254.987 
  NoData Value=nan 
  Metadata: 
    STATISTICS_MAXIMUM=2424.2099609375 
    STATISTICS_MEAN=317.65072388322 
    STATISTICS_MINIMUM=54.810001373291 
    STATISTICS_STDDEV=254.98702538825

Now we know that EPSG:4258 (ETRS89) should be taken and tiling applied; in our case, 4500 px will be good approach. Using copy, it will be done faster.

raster2pgsql -s 4258 -C -I -l 2,4,8 -t 4500x4500 -F -Y *.tif raster_ops.dem | psql -d mastering_postgis -U osm

We need to provide port and host name to psql for the command to work.

If you don't use -C flag during import, probably the AddRasterConstraints() function will be used later to fill in correct values in the raster_columns catalog.

Table of Contents for
Mastering PostGIS

Preparing data

Table of Contents for Mastering PostGIS

Table of Contents for
Mastering PostGIS