What is the GSI file format?
.gsi files store Golden Software Interchange data - a proprietary binary format for transferring map and graphical entity data between Golden Software's scientific visualization applications, primarily Surfer (contour and 3D surface mapping) and MapViewer (thematic mapping).
The format encodes vector and raster graphical entities - polygons, lines, labels, and their associated attributes - in a binary record structure. It functions as an internal interchange medium rather than a general GIS standard; .gsi is not OGC-compliant and no third-party readers exist. No public specification or magic byte signature is documented.
Voxler, a Golden Software 3D visualization tool that also used .gsi, was retired in 2024 with its capabilities absorbed into Surfer. The current Surfer (version 31.x as of 2026) continues to support .gsi. File sizes range from kilobytes to tens of megabytes depending on map complexity.
Users outside the Golden Software ecosystem should export to standard GIS formats via Surfer - such as SHP, KML, or GeoTIFF - since no independent import path for .gsi exists. The format is Windows-only.
Security & safety
RISK: LOWGSI is a passive binary data file specific to Golden Software products. No known security vulnerabilities or exploit vectors. Not executable and not interpreted outside the Golden Software ecosystem.
Format details
in a nutshell- Subtitle Workshop / subtitle format index - Some European subtitle tooling uses .gsi as a header file for EBU STL subtitle format (EBU Tech 3264); distinct from Golden Software GSI and processed by subtitle editors.
Programs that open GSI files
Windows2 apps
Golden Software Surfer
Paid File > Open, select the .gsi file. Surfer reads GSI as a graphical interchange file for map data. 
Technical details
deep spec| Encoding | Binary (proprietary Golden Software container) |
| Byte order | Little-endian (Windows-native Golden Software applications) |
| Content types | Vector entities (polygons, lines, labels), raster datasets, map legends, attribute data |
| Primary purpose | Interchange medium between Surfer, MapViewer, and Didger within the Golden Software suite |
| Compression | Uncompressed binary records - no compression documented in Golden Software help resources |
| Integrity checking | No file-level checksum or integrity mechanism documented |
| Typical file size | KB to tens of MB (scales with map entity count and raster data volume) |
| Platform | Windows only |
| OGC compliance | None - not a standard GIS interchange format; no third-party reader exists |
| Conversion path | Export to SHP, KML, or GeoTIFF via Surfer for use in external GIS applications |
| Related Golden Software formats | .gsm (Golden Software Mosaic), .grd (Surfer grid file), .bln (blanking file) |
| Voxler status | Voxler (retired 2024) formerly used .gsi; its 3D capabilities were absorbed into Surfer |
| Developer | Golden Software, LLC (makers of Surfer, MapViewer, Didger, and Grapher) |
| Released | circa 1990s (with early Surfer/MapViewer releases by Golden Software) |
| Latest version | Current (supported in Surfer 31.x as of June 2026); no versioning info publicly documented |
| Specification | surferhelp.goldensoftware.com |
GSI conversions
Community Q&A
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