Convert GSI to DLG

Understanding GSI and DLG file formats

GSI (Geographic Survey Institute) files are geospatial data files commonly used in Japan for storing survey and mapping information. These files typically contain vector data representing geographic features such as boundaries, roads, and elevation points.

DLG (Digital Line Graph) files are a standard format developed by the US Geological Survey (USGS) for representing vector map data. DLG files are widely used in GIS (Geographic Information Systems) for storing features like hydrography, transportation, and boundaries in a structured, interoperable format.

Why convert GSI to DLG?

Converting GSI files to DLG format allows for broader compatibility with GIS software and easier integration with USGS datasets. This conversion is essential for users who need to work with Japanese geospatial data in systems that primarily support DLG files.

How to convert GSI to DLG

There is no direct, one-click converter for GSI to DLG due to the specialized nature of both formats. However, the conversion can be achieved through a two-step process using GIS software that supports custom import/export operations.

1. Convert GSI to a common GIS format (such as Shapefile or GeoJSON) using specialized GIS tools or scripts. QGIS is a free, open-source GIS application that supports a wide range of vector formats and can be extended with plugins for additional format support.
2. Convert the intermediate format to DLG using GIS software or dedicated conversion tools. While QGIS does not natively export to DLG, you can use GDAL/OGR command-line tools or specialized utilities to convert from Shapefile or GeoJSON to DLG.

Recommended software for GSI to DLG conversion

• QGIS: Import GSI data (with plugins or scripts), then export to Shapefile or GeoJSON via Layer → Export → Save Features As....
• GDAL/OGR: Use the ogr2ogr command-line tool to convert from Shapefile/GeoJSON to DLG. Example command:
  ogr2ogr -f "DLG" output.dlg input.shp

Tips for successful conversion

• Ensure attribute fields and coordinate systems are preserved during each conversion step.
• Check for data loss or geometry errors after each conversion, especially when moving between formats with different capabilities.
• If you encounter issues, consult the documentation for QGIS and GDAL/OGR, or seek community support for custom scripts.