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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">I was comparing some alternative scenarios for data exports, and I was a bit surprised when I noticed that GeoJSON output from ogr2ogr is really slow.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I used these lake polygons as test data <a href="https://wwwd3.ymparisto.fi/d3/gis_data/spesific/ranta10jarvet.zip">
https://wwwd3.ymparisto.fi/d3/gis_data/spesific/ranta10jarvet.zip</a> and I tested on Windows with GDAL 3.11.0dev-181b6b9991, released 2024/11/21.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I was thinking that maybe it is slow to write JSON just because it is text based format so I made tests also with other text formats (GML, MapInfo MIF, and CSV). My commands and timings:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">ogr2ogr -f geojson lakes.json jarvi10.shp --config cpl_debug on --config cpl_timestamp on<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">220 sec - 1000 features/sec<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">ogr2ogr -f "mapinfo file" lakes.mif jarvi10.shp --config cpl_debug on --config cpl_timestamp on<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">110 sec – 2000 features/sec<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">ogr2ogr -f gml lakes.gml jarvi10.shp --config cpl_debug on --config cpl_timestamp on<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">92 sec - 2300 features/sec<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">ogr2ogr -f csv lakes.csv jarvi10.shp -lco geometry=as_wkt --config cpl_debug on --config cpl_timestamp on<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">77 sec - 2800 featurs/sec<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Then I pondered if I know any other tools for exporting GeoJSON, and SpatiaLite came into my mind. ExportGeoJSON
<a href="https://www.gaia-gis.it/gaia-sins/spatialite-sql-5.1.0.html">https://www.gaia-gis.it/gaia-sins/spatialite-sql-5.1.0.html</a> from GeoPackage into GeoJSON file was 4 times faster than ogr2ogr.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">select exportgeojson('vgpkg_jarvi10','geom','c:\data\jarvet\fromspatialite.json');<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">54 sec - 4000 features/sec<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">For calibrating the speedometer, I converted data also from shapefile into GeoPackage<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">ogr2ogr -f gpkg lakes.gpkg jarvi10.shp --config cpl_debug on --config cpl_timestamp on<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">12 sec - 18000 features/sec<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I made also a couple of tests with geojsonseq output but I did not notice much difference. Does writing GeoJSON require some tricks that other formats do not require, or why it is so slow?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">-Jukka Rahkonen-<o:p></o:p></span></p>
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