gis

Fix R leafem customizeLayersControl where includelegends=TRUE fails to show legends in Leaflet layers control. Step-by-step solution for group matching, common pitfalls with addLegend, and alternatives like htmlwidgets onRender for R leaflet maps.

Optimize large polygon datasets in PostGIS for zoom-based rendering. Use GiST/BRIN indexes, ST_ClusterKMeans, ST_ClusterWithin, vector tiles (MVT), geometry simplification for millisecond queries on 300k+ records.