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qtVlm vs GWeatherRouting: catalog facts
qtVlm	GWeatherRouting
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Best for: Cruising and racing sailors who plan routes around weather	Best for: Sailors planning coastal or offshore routes with weather forecasts
Free + paid options The GRIB viewer is free; mobile and tablet apps, chart packs and the GRIB service are paid.	Free Free and open source under GPL-3.0-or-later.
Windows, Android, iOS	Windows, Linux
Weather routing with departure-time comparison Reads S57, S63, raster and MBTiles charts AIS and NMEA instrument support Iridium GO certified	Plans routes using GRIB weather data and boat polar diagrams Imports and exports GPX points and tracks Supports chart formats including GeoJSON, KAP, and GeoTIFF Available for Linux and Windows
Mobile versions and chart packs are paid Wide feature set takes time to learn	The listed downloads are for Linux and Windows
Downloadable app	Downloadable app
Not open source	Open source
License not stated	License: GPL-3.0-or-later
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Sources for qtVlm meltemus.com apps.apple.com/us/app/qtvlm/id999110023 Catalog checked September 24, 2026	Official website Full listing and sources Sources for GWeatherRouting gweatherrouting.org Catalog checked October 8, 2026

“Not stated” means we have not confirmed it. Features can vary by device and plan.

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