Convert KMZ to BSB

Understanding KMZ and BSB file formats

KMZ is a compressed file format used by Google Earth and other mapping applications. It contains placemarks, paths, and overlays in KML (Keyhole Markup Language) format, often bundled with images and other resources. BSB is a raster chart format primarily used for nautical charts, especially in marine navigation software. BSB files store georeferenced raster images and metadata, making them suitable for use in electronic chart display systems.

Why convert KMZ to BSB?

Converting KMZ to BSB is useful for mariners and navigators who want to use custom map overlays or placemarks from Google Earth in marine navigation software that supports BSB charts. This conversion allows for the integration of user-generated or third-party map data into professional navigation systems.

How to convert KMZ to BSB

Direct conversion from KMZ to BSB is not straightforward, as these formats serve different purposes and structures. The process typically involves several steps:

1. Extract the KML from the KMZ file by unzipping it.
2. Convert KML overlays or placemarks to a georeferenced raster image (such as GeoTIFF) using GIS software like QGIS.
3. Export the raster image as a GeoTIFF or similar format.
4. Convert the GeoTIFF to BSB format using specialized tools such as MapCal (part of the OpenCPN suite) or BSBChartMaker.

Recommended software for KMZ to BSB conversion

• QGIS: Free and open-source GIS software for converting KML/KMZ overlays to raster images. Use Layer → Export → Save As to export as GeoTIFF.
• BSBChartMaker: A tool for converting georeferenced raster images (like GeoTIFF) to BSB format.
• MapCal (OpenCPN): Used for calibrating and converting raster images to BSB charts for marine navigation.

Step-by-step conversion workflow

1. Unzip the KMZ file to extract the KML and any associated images.
2. Open the KML in QGIS and overlay it on a base map.
3. Export the map as a georeferenced raster image (GeoTIFF).
4. Open the GeoTIFF in BSBChartMaker or MapCal and follow the instructions to create a BSB chart.

Conclusion

While there is no direct one-step converter for KMZ to BSB, using GIS and chart-making tools like QGIS and BSBChartMaker allows you to achieve this conversion through a series of manageable steps. This enables the use of custom map data in marine navigation systems that support BSB charts.