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qtVlm is a free, donation-supported navigation and weather software program from France for Mac and PC there are also iOS and Android versions, but they are not free.

It is an internationally popular product with versions in multiple languages. It is the leading program worldwide for tracking and taking part in ocean races presented online. The name comes from "Qt," a cross-platform programming system, and "VLM," which stands for Virtual Loup de-Mer, a web-based real-time sailboat racing simulation.

It shows both RNC charts (images of paper charts) and has a top of the line vector ENC presentation (S-57 and S-63), as well as others including the global set of ENC training charts called CM-93. It will also show OpenStreetMap and OpenSeaMap files, and others, including the economic set of official international ENC called Meltemus charts.

For weather work, it can georeference graphic weather maps and related images, as well as display GRIB formatted model forecasts. It includes several routing options for optimum sailing routes across numerical wind, wave, and current forecasts based on your vessel's polar diagram of performance specs.

It shows live global weather observations from buoys, stations, and ship reports, and then does a time and space interpolation of (up to three) loaded weather model data to compare with the observations.

Other unique features include:

Graphic display of US forecast zone boundaries with latest forecast for US coastal, offshore, and high seas zones.

Sail or power boat simulator, with many options, including depth sounder simulation and user defined current flow. Use real forecasts or simulated wind.

Unique search engine lets you find landmarks by name or ENC objects by specific properties (i.e., find all rocks that dry more than 5 ft); search all charts loaded or just a selected region.

Practice vessel maneuvers with the simulator in live AIS traffic in any part of the world.

Add official USGS elevation contours to the land in any US waters to study wind flow or piloting options.

Implements an anti-grounding cone feature usually found only on official ECDIS programs that triggers alarms at all dangers (orange) and obstacles (red).

Includes a route checker function that searches a saved route for hazards within a chosen cross-route distance, which is a required function of ECDIS but rarely seen on an ECS.

Includes a state of the art NOAA chart interface. Select an area of interest, right click to learn what charts are available, and if they are already loaded, and if so, which are outdated, then with a button click you can load or update as needed. NOAA ENC are updated daily.

Option to show ENC history of changes that took place by actually viewing the chart updates sequentially.

Includes unique cursor pick option to highlight area objects selected.

Here is a sample use of the program showing what led to the grounding of the Ever Given in the Suez canal.

Numerous other useful features are available that contribute to the product's popularity. Read more about qtVlm and download the program and detailed manual from the parent company here:


The program has an excellent manual, but we also have added more support since we use the program in our Marine Weather and Electronic Chart Navigation courses:

Video playlist of tutorials and examples

Cheat Sheet for details on various functions

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