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VRT to merge vector data

✓ Published0🌍 Public

Last edited Sep 17, 2021

Created on Sep 17, 2021

This example demonstrates how to merge multiple vector datasets into a single unified dataset using the Virtual Dataset (VRT) format, specifically for French IRIS geographic zones. It shows the workflow of combining shapefiles from different territories and projections into one WGS 84 layer without creating an intermediate file, then converting the result to GeoPackage and PostGIS formats. The code uses the `ogrmerge.py` GDAL utility to create the VRT, `ogr2ogr` for format conversions, and psql commands for database setup.

AI-generated description

VRT to merge vector data

Intro

Adopte le VRT, cela changera ta vie. Exemple: les IRIS par territoire. Je veux une sortie WGS 84. Avec le VRT, je ne crée pas de fichier immédiatement

Recipe

Retrieve data and uncompress

Download

for i in $(cat<< EOF
ftp://Iris_GE_ext:eeLoow1gohS1Oot9@ftp3.ign.fr/IRIS-GE_2-0__SHP_LAMB93_FXX_2021-01-01.7z
ftp://Iris_GE_ext:eeLoow1gohS1Oot9@ftp3.ign.fr/IRIS-GE_2-0__SHP_RGAF09UTM20_R01_2021-01-01.7z
ftp://Iris_GE_ext:eeLoow1gohS1Oot9@ftp3.ign.fr/IRIS-GE_2-0__SHP_RGAF09UTM20_R02_2021-01-01.7z
ftp://Iris_GE_ext:eeLoow1gohS1Oot9@ftp3.ign.fr/IRIS-GE_2-0__SHP_UTM22RGFG95_R03_2021-01-01.7z
ftp://Iris_GE_ext:eeLoow1gohS1Oot9@ftp3.ign.fr/IRIS-GE_2-0__SHP_RGR92UTM40S_R04_2021-01-01.7z
ftp://Iris_GE_ext:eeLoow1gohS1Oot9@ftp3.ign.fr/IRIS-GE_2-0__SHP_RGM04UTM38S_R06_2021-01-01.7z
EOF
);
do wget $i;
done;

Uncompress

for i in *.7z;
  do 7z x $i;
done;

Manipulate with GDAL utilities

Merge with VRT

SHAPE_ENCODING=ISO-8859-1 \
ogrmerge.py -single -o iris_ge_france_entiere_wgs84.vrt IRIS-GE_2-0__SHP_*/*/1_*/*/IRIS_GE.SHP -overwrite_ds -t_srs "EPSG:4326" -f VRT -nln iris_ge_france_entiere_wgs84

Convert to GPKG

ogr2ogr -f GPKG iris_ge_france_entiere_wgs84.gpkg iris_ge_france_entiere_wgs84.vrt -nln iris_ge_wgs84 -nlt PROMOTE_TO_MULTI

Export to PostGIS table

Set variable

export PGHOST=localhost
export PGPORT=5432
export PGDATABASE=my_database
export PGUSER=my_password
export PGPASSWORD=my_user

Create schema

psql -c "CREATE SCHEMA IF NOT EXISTS administratif"

Load to database in the "right schema"

ogr2ogr -f "PostGreSQL" \
        PG:"host="$PGHOST" port="$PGPORT" dbname="$PGDATABASE" user="$PGUSER" password="$PGPASSWORD"" \
        iris_ge_france_entiere_wgs84.vrt iris_ge_france_entiere_wgs84 \
        -lco OVERWRITE=yes \
        -lco SCHEMA=administratif \
        -lco SPATIAL_INDEX=GIST \
        -lco GEOMETRY_NAME=the_geom \
        --config PG_USE_COPY YES \
        -nlt PROMOTE_TO_MULTI \
        -nln iris_ge_wgs84 \
        -lco FID=fid \
        -a_srs "EPSG:4326"

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