Vakaros VKX Files Are Now Supported on SailingMetrics

SailingMetrics now supports Vakaros VKX files. If you sail with an Atlas 2 or Atlas Edge, you can upload your sessions directly and get the same depth of analysis that GPS track users have always had, plus a number of things that only the VKX format makes possible. This post explains what that means in practice, how to get your data across, and what you will find in your analysis once it is there.

What the Vakaros Atlas Is and Why It Produces Better Data

The Vakaros Atlas 2 is built around a dual-band L1+L5 GNSS receiver that captures position at up to 25 Hz, meaning a fix up to twenty-five times per second. Most smartphone GPS chips manage once per second, sometimes once every two. Positional accuracy sits at a few centimetres when conditions are good. The Atlas can detect speed changes that happen over a fraction of a second and position shifts that ordinary GPS logging misses entirely.

Beyond the GNSS receiver, the Atlas 2 carries a three-axis magnetometer with 0.1-degree heading resolution, a three-axis gyroscope, and a three-axis accelerometer. It can also connect to external sensors including Cyclops load cells, wind sensors, and other transducers, pulling everything into a single log file. A full day on the water produces one recording that captures the state of the boat with a completeness that simply was not possible with consumer sailing instruments a few years ago.

The device logs all of this automatically while you are sailing. No need to press record. When you come off the water, you open the Vakaros Connect app, sync the session over Bluetooth or Wi-Fi, and the recording is on your phone ready to export.

The VKX Format: What It Is and Why It Matters

VKX is Vakaros's own binary telemetry log format and the native output of every Atlas device. When you export a session from the Vakaros Connect app, you can choose GPX or CSV, but those formats drop most of what makes Vakaros data worth having. The VKX file is the complete record. Everything the device captured is in there.

The format is structured around rows, each with a key that identifies the data type and a fixed-size payload. It is compact and fast to write, which matters when you are logging at 10 Hz on a battery-powered instrument. Page headers appear roughly every two kilobytes and record the log format version, so files from different firmware versions can all be parsed correctly.

For analysis, three things about VKX matter most. The first is the full sample rate. When you export as GPX, you typically get one position per second. The VKX file keeps every sample the device recorded, at whatever frequency you had set. A good tack can unfold in under two seconds, and a one-second sampling rate easily misses the shape of it.

The second is the IMU data. VKX files carry heading, heel, and pitch from the onboard sensors alongside the GNSS positions. The analysis is no longer just about where the boat went but about how it was oriented throughout the session. Heel angle through a tack, pitch angle on a wave, the relationship between heading and course-over-ground as leeway changes: all of that travels with the file.

The third, particularly useful for racing, is the start line data. If you set up the start line in the Vakaros app before the race by pinging the committee boat and the pin end, those positions are embedded in the file, along with the starting gun time. SailingMetrics reads all of that and adds it to the analysis automatically.

How to Export a VKX File from the Vakaros App

The export process takes about a minute. Open the Vakaros Connect app and tap the Sessions tab, which shows all the sessions the app has pulled from your Atlas. Find the one you want, tap to open it, then tap the share or export icon in the top right corner. The app offers a choice of formats. Select VKX. The file is created and you can send it via the standard iOS or Android share sheet, email it to yourself, or save it to your files.

Then open SailingMetrics in any browser, go to the upload page, and drop the VKX file in. The importer detects the format automatically.

VKX files are larger than GPX files from the same session, especially at 5 or 10 Hz. A full day logging at 10 Hz can run to several megabytes. On a decent connection that uploads quickly, but it is worth knowing if you are somewhere with slow Wi-Fi.

One thing to check before you export: if you raced, make sure the start line was set in the app before the start and that the gun time was recorded. That data is only in the file if it was captured at the time. You cannot add it afterwards. If it is there, SailingMetrics picks it up automatically. If it is not, the rest of the session analysis still works in full.

What You See When You Upload a VKX File

Once processed, your session opens like any other activity on SailingMetrics, with the full GPS replay on the map and speed over ground, VMG, and course over ground plotted over time. The difference you notice first is the resolution of the speed trace. With one-second GPS data you get a stepped, blocky line. With 10 Hz Vakaros data it curves smoothly, showing the actual acceleration out of a tack, the speed drop on approach to a mark, and the recovery as you settle onto the new course.

Tack detection is sharper as a result. With one-second data the software finds a course-over-ground reversal and estimates the minimum speed from the samples on either side. With 10 Hz data it has fifty times as many points and can pinpoint the exact moment the bow came through the wind, the true minimum speed, and the precise shape of the recovery. The speed loss figures in the tack analysis section reflect what actually happened rather than what the algorithm could infer from sparse samples.

VMG analysis also benefits. The metric is calculated from speed and course-over-ground, and both inputs are cleaner at higher frequency. Fluctuations that get averaged away in one-second data become visible at 10 Hz: the brief VMG gain as you find pressure in a gust, or the small loss as the bow comes up on a wave before you bear off again. Whether you use these to tweak your upwind technique or just to understand what was happening on a particular leg, having them available is useful.

Heel and Heading Data

The IMU data in a VKX file is one of the bigger differences between uploading from a Vakaros and uploading a standard GPS track. In the session view you will see a heel angle chart beneath the speed chart, showing how heeled the boat was throughout the session.

This becomes interesting at specific moments. Pull up a tack and watch what the heel does through the manoeuvre. Did the boat heel to windward as the bow came through the wind, and for how long? Did it spike on the new tack before you were fully sheeted in? These patterns are hard to read from speed data alone but show up clearly when heel is alongside it.

The heading data lets SailingMetrics show the difference between your heading and your course over ground, which is your leeway angle. On a beat, this is the gap between where the bow is pointing and where the boat is actually going. Comparing leeway on port versus starboard, or across different wind strengths, tells you things about your rig setup and technique that GPS position data on its own cannot get at.

Pitch is also captured and is most relevant for offshore or keelboat sessions where the boat is moving through swell. High pitch angles upwind often track with increased drag and lower VMG. The relationship is not always visible on the water in the moment, but when you lay pitch and boat speed alongside each other across a session, the correlation tends to be pretty clear.

Vakaros and Race Starting Analysis

The start is where many club races are decided, and the Vakaros Atlas is built with this in mind. Before the race you sail along the line and ping the two ends using the button on the device. The app stores the positions of the committee boat and the pin end. When the gun fires, the Atlas records the time.

Upload a VKX file that contains this data and SailingMetrics adds start-specific analysis to the session. You can see where you were on the line at the gun, expressed as distance from each end. You can see how many seconds you crossed before or after the gun. And you can replay the pre-start manoeuvring with the line drawn on the map, which makes the geometry of your approach much easier to read than trying to reconstruct it from memory.

Over a season this builds into a picture of your starting habits. If you consistently end up in the middle of the line when the pin was favoured, you will see that. If you tend to be over early and then have to duck back through the fleet, that shows up too. Start performance is one of the hardest things for sailors to assess accurately without data, and having it from every race makes it a lot easier to find the patterns that are actually costing you places.

Using Vakaros Data Alongside Video

If you record video of your sessions, SailingMetrics synchronises it with the VKX data using the timestamps in the file. Because the Atlas logs from the moment you go sailing and the timestamps are accurate to the millisecond, the synchronisation is tighter than what you get when aligning video with a manually started GPS recording.

In practice this means the tack video clips in the body movement analysis match up precisely with the IMU and GNSS data from the VKX file. When you watch a clip, the heel angle, heading, and speed traces below it are showing you the state of the boat at exactly the same moments as the video. That combination is what makes it possible to watch a tack and understand what the numbers are telling you about it, rather than just seeing the numbers and the video separately.

If you are not currently recording video, a phone in a waterproof mount facing aft is enough to get started. The VKX file handles the position and performance data; the video adds the visual layer that turns the numbers into something you can act on.

How to Make the Most of High-Frequency Data

If you are new to 10 Hz sailing data, the traces can look noisier at first than what you are used to from phone GPS. Some of that noise is real: genuine variation in speed and heading that lower-frequency logging was averaging away. Some of it is measurement noise from the sensors. Before drawing conclusions from any single spike or dip, check whether the variations are correlated with events you remember from the session or whether they look random.

For tacks and gybes, the higher sample rate is almost always worth having. The detail you gain on the shape of the speed loss and recovery curve more than makes up for a bit more noise to look past. For comparing average VMG across long upwind legs, the benefit is smaller because you are averaging over many seconds anyway, and the difference between 1 Hz and 10 Hz mostly washes out.

Storage and battery are rarely a constraint with the Atlas 2, which has over 100 hours of battery life and plenty of onboard memory. Logging at 10 Hz for most day sailing is fine. The one case where you might choose a lower rate is a multiday offshore event where you want to keep file sizes manageable. SailingMetrics handles 2 Hz, 5 Hz, and 10 Hz VKX files correctly.

Who This Is For

VKX support is useful for any sailor using a Vakaros Atlas device: club racers who use the Atlas as their main race instrument, Olympic and professional sailors who log data as part of a broader training setup, and anyone who has an Atlas primarily for the on-water display and wants to do something with the session data afterwards.

If you have been uploading GPX exports from the Vakaros app, switching to VKX will improve the tack analysis right away and add the heel, heading, and pitch data that GPX does not carry. The only change to your workflow is selecting VKX instead of GPX when you export from the Vakaros Connect app.

If you have older sessions that you exported as GPX, you can go back into the Vakaros app, re-export them as VKX, and re-upload to SailingMetrics. The original session data stays in the app unless you have deleted it.

For coaches working with athletes who use Vakaros devices, VKX support means you are looking at the full resolution of what the device recorded rather than a downsampled version of it. When you sit down with an athlete to review a tack, the data in front of you reflects what actually happened. That tends to make the conversation more specific and the things you want to fix easier to identify clearly.

Getting Started

SailingMetrics is an independent platform. This integration was built using Vakaros's publicly documented VKX format and is not affiliated with or endorsed by Vakaros.

If you already have a SailingMetrics account, you can upload a VKX file now from the activity upload page. The importer recognises the format automatically. If you are new to SailingMetrics, create a free account and start with one of your recent Vakaros sessions to see what the analysis looks like.

The Vakaros device documentation covers how to configure logging frequency, set up the start line, and export sessions from the Connect app. If anything in the upload process is unclear, or you have questions about what you are seeing in the analysis, the contact page is the best place to reach us.

We have more coming for Vakaros data over the next few months: cross-session comparison of heel and heading, and deeper tools around the start line analysis. If there is something specific you want from the data you are already logging, let us know. The more we hear from sailors actually using these devices, the more useful we can make it.