Choosing the Right Projection for Area & Distance Analysis

A common pitfall in web mapping pipelines is running buffer or polygon area calculations directly in EPSG:3857 (Web Mercator). Because scale distortion grows rapidly away from the equator, metric measurements can be off by 2x or more at mid-to-high latitudes.

1. Recommended CRS Strategy

• Storage & Exchange: Keep canonical datasets in WGS 84 (EPSG:4326) or GeoParquet with explicit CRS metadata.
• Regional Area Analysis: Reproject to an equal-area projection such as Albers Equal Area or Mollweide.
• Local Distance & Buffers: Use the local UTM zone (EPSG:326xx / 327xx) or PostGIS geography type.

2. Fast Batch Reprojection with ogr2ogr

ogr2ogr -f "GPKG" -t_srs EPSG:32618 output_utm18n.gpkg input_wgs84.geojson