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Analyzing and predicting crop data in the Netherlands

I found QGIS extremely handy in exploring datasets, debugging and inspecting errors.

Requirements

Postgres + PostGIS gdal: brew install gdal --enable-unsupported --with-postgresql

Data sources

Loading basisregistratie-gewaspercelen-brp from an ESRI file geodatabase (.gdb) using R

refs: https://data.overheid.nl/data/dataset/basisregistratie-gewaspercelen-brp https://geodata.nationaalgeoregister.nl/brpgewaspercelen/atom/brpgewaspercelen.xml http://gis.stackexchange.com/questions/151613/how-to-read-feature-class-in-file-geodatabase-using-r

Dataset download links can be found in: http://geodata.nationaalgeoregister.nl/brpgewaspercelen/atom/brpgewaspercelen.xml

importing data into PostGres

SRID 28992

// Converting GDB files to Shape files

ogr2ogr -f "ESRI Shapefile” destination_data.shp BRP_Gewaspercelen_2009.gdb

// Importing shape files to postgres

shp2pgsql -I -s 28992 2012.shp 2012 | psql -p 5433 -U postgres -d crops
shp2pgsql -I <PATH/TO/SHAPEFILE> <SCHEMA>.<DBTABLE> | psql -U postgres -d <DBNAME>

Preparing Database

// fix geometries alter table "2014" add column geom_fixed geometry; update "2014" set geom_fixed = ST_makeValid(geom); CREATE INDEX geom_fixed_2014_gix ON "2014" USING GIST (geom_fixed);

// add centeroid of geoms alter table "2016" add column center geometry; update "2016" set center= ST_SetSRID(ST_Centroid(geom_fixed),28992); CREATE INDEX centroid_2016_gix ON "2016" USING GIST (center);

//create foreign key indexes on each table

alter table "2015" add column next_year_parcel_fk integer REFERENCES "2016" (gid); update "2015" set next_year_parcel_fk="2016".gid from "2016" where ST_CoveredBy("2016".center,"2015".geom_fixed) -- and (st_area(st_intersection("2015".geom_fixed,"2016".geom_fixed))/("2016".shape_area)) > 0.6

A more accurate alternative would probably be:

update "2015" set next_year_parcel_fk="2016".gid

from "2016" where ST_Intersects("2016".geom_fixed,"2015".geom_fixed) and (st_area(st_intersection("2015".geom_fixed,"2016".geom_fixed))/("2016".shape_area)) >0.8

// creating the fishnet

get bounding box of the 2009:
xmin ymin:
12856.7 305608.34, 
xmax, ymax 
277980.31 613446.06

— 
create fish nets 
CREATE TABLE fishnet (gid serial, cell geometry);
insert into fishnet (cell)

(SELECT cell FROM 
(SELECT (
ST_Dump(makegrid_2d(ST_GeomFromText('Polygon((12856.7 305608.34, 12856.7 613446.06, 277980.31 613446.06, 277980.31 305608.34, 12856.7 305608.34))',
 28992), -- WGS84 SRID
 10000) -- cell step in meters
)).geom AS cell) AS q_grid
)

based on bounding box :

get bounding box of the 2009:
xmin ymin:
12856.7 305608.34, 
xmax, ymax 
277980.31 613446.06

// assign fishnet id to each parcel in each year

alter table "2009" add column cell_id integer ; update "2009" set cell_id = fishnet.gid from fishnet where ST_CoveredBy("2009".center,fishnet.cell)

// importing soil data

https://snorfalorpagus.net/blog/2016/03/13/splitting-large-polygons-for-faster-intersections/

// add soil types to reference table

alter table "2016" add column soil character varying ; 
alter table "2016" add column soil_code smallint ;  

update "2016" 
set soil = soil_map_dump.omschrijvi,  soil_code=soil_map_dump.gronds
from soil_map_dump where ST_CoveredBy("2016".center,soil_map_dump.geom)

Import db dump into PostGres

gunzip -c crops_pgdump_march1.gz | psql your_db_name

Indexing

vacuum analyze  "2010"

fix polygons check if geometries are valid: select gid from soil_map where ST_isvalid(soil_map.geom)=false

update "soil_map" set geom_fixed = ST_MakeValid(geom)