Convert BNA to TOPOJSON Online - Free & Fast

What is BNA?

Atlas Boundaries (BNA) is a simple ASCII coordinate format for storing polygon boundary data, originally developed by Atlas GIS for representing area features like postal codes, sales territories, and administrative regions as coordinate lists.

What is TOPOJSON?

TopoJSON is an extension of GeoJSON that encodes topology, sharing boundary arcs between adjacent features to dramatically reduce file size for map data.

When Should You Use BNA vs TOPOJSON?

BNA vs TOPOJSON: Key Differences

• •The core technical difference: BNA relies on lossy compression whereas TOPOJSON uses lossy compression.
• •Since both BNA and TOPOJSON use lossy compression, the quality characteristics are comparable — differences in file size come down to how efficiently each format implements compression.
• •Alpha channel support: TOPOJSON lacks transparency support.
• •File sizes: BNA files typically range 1KB to 50MB depending on boundary complexity and TOPOJSON files 80% smaller than equivalent GeoJSON for administrative boundaries.
• •Use case fit: BNA targets atlas gis boundary exchange, regional mapping, legacy spatial data conversion and TOPOJSON targets web choropleth maps, data visualization, boundary simplification — your choice depends on which workflow stage you are serving.

Advantages of BNA

• ✓BNA applies lossy compression specifically calibrated for Atlas GIS boundary exchange, regional mapping, legacy spatial data conversion.
• ✓BNA enjoys broad native support across operating systems, browsers, and creative tools alike.
• ✓BNA delivers impressive compression ratios, shrinking files dramatically while keeping visual quality high.
• ✓You will find BNA support built into virtually every tool that handles Atlas GIS boundary exchange, regional mapping, legacy spatial data conversion — no plugins or converters needed.

Advantages of TOPOJSON

• ✓At its core, TOPOJSON relies on lossy encoding — a design choice that makes it perfect for Web choropleth maps, data visualization, boundary simplification.
• ✓You won't run into compatibility issues with TOPOJSON — it's a universal standard across platforms.
• ✓File size management with TOPOJSON: aggressive compression with minimal visible quality loss.
• ✓Every major application in the Web choropleth maps, data visualization, boundary simplification space supports TOPOJSON natively.

Common Use Cases for BNA to TOPOJSON Conversion

Industry Applications

Best Practices for BNA to TOPOJSON Conversion

• →When converting BNA to TOPOJSON: confirm the coordinate reference system (CRS / projection) is preserved or explicitly reprojected
• →Keep attribute tables and feature metadata intact — TOPOJSON should retain all fields from BNA
• →Check geometry types (point, line, polygon) map cleanly between the two formats
• →Verify that z/elevation values and topology survive the conversion when working with terrain data
• →Always keep a backup of your original files before converting
• →Choose the appropriate quality settings for your specific use case

Troubleshooting BNA to TOPOJSON Conversion

• !TOPOJSON features land in the wrong place after BNA to TOPOJSON → verify the CRS/projection; mismatched coordinate systems shift geometry
• !Attribute columns missing in TOPOJSON → some GIS formats have field name length or type limits; rename or cast columns first
• !BNA to TOPOJSON drops the z/elevation dimension → pick a target format that supports 3D geometry
• !TOPOJSON file won't open in your GIS app → confirm the format version and any required sidecar files (e.g. .prj, .shx) are present

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