Lap Legend User Guide

Welcome to Lap Legend, The Ultimate Motorsports Lap Timing and Data Acquisition App!

Disclaimers

This app is intended only for sanctioned motorsports and track events. Always drive safely. Use at your own risk.

Any telemetry, signaling, or communication features are not guaranteed, and must not be relied upon for critical or safety uses.

Getting Started

1. Accept any permissions prompts so that the app can use your GPS and other features you’ve selected
2. Mount your phone or tablet securely to the vehicle, and ensure it has a clear line-of-sight to the sky. A windshield mount can be a good option.
3. Choose the track you’ll be driving at, by tapping on the top menu item
4. For autocross and custom course setup: See Here
5. If you want to record video, use an external GPS, or OBD / sensors, use the menu to go enable and configure those
6. Press the “Start Driving” button on the main menu

Want to know more about how to drive your car on a race track? See: Where to Drive Your Car on a Race Track

Driving Screen

Your dashboard while recording a driving session.

When you’re done driving, tap on the lap timer display and answer the prompt to end the driving session.

Tip: You can customize the data display boxes at the bottom by tapping on them, and then selecting the data channel of your choice.

Once you cross the start line, you’ll see the timer start to run. When you cross the finish line, your completed time will be shown flashing for 15 seconds. Green means it’s a new best lap for this session. Magenta means it’s a new personal best lap time for this track.

When doing multiple laps, the timer will change to show your predicted completed lap time for the current lap (not flashing, and with the word “Predict” at the top). This will go up or down in real time depending on how well you drive this lap, corresponding with the predicted delta time / bar at the top. It will also display your last, best, and target lap times below.

The Target lap time is also known as your theoretical best lap time and is based on your best individual sector times so far during this session. It’s an estimate of what you can do if you put it all together into one lap.

Using your Phone’s Internal GPS

Although a phone’s internal GPS can be used successfully, and is an easy way to get started with this app, you do need to be thoughtful about how and where you mount it so that it can get a good signal. What might be sufficient while parked or driving on the street may degrade when driving at race track speeds.

The #1 reason people could have a poor experience with an app of this type is due to GPS reception problems. As the old saying goes, “garbage in = garbage out”. The good news is that there are multiple ways you can improve or solve this.

• Mount the phone securely, in a place where it has a clear line-of-sight to the sky. A windshield mount can help with this.
• Try to avoid placing it near, or especially under, anything metal.
• Avoid cup holders, pockets, glove boxes, or anywhere that does not firmly hold it in place. You really want an actual mount for best results.
• Keep the app open and the screen on. Background mode produces poor results.

Using an External GPS for Best Results

When you want a solid GPS solution that provides improved signal reception, data sample rate, and accuracy, many users choose a dedicated external GPS unit. This greatly improves lap timing accuracy and driving line analysis, making Lap Legend on your phone or tablet comparable to dedicated motorsports data acquisition devices. Please note that mounting location and reception conditions are still important for best results.

As of version 1.5, Lap Legend supports receiving live GPS data from the following options:

As noted above, Lap Legend also contains universal support for GPS devices that provide standard NMEA-0183 data via certain BLE services (not common yet), and when on Android, classic Bluetooth Serial Port Profile (SPP). This capability is provided on an as-is basis. Compatibility and performance can vary depending on your GPS and device.

At this time we do not directly support other GPS devices than what is listed, but if you have a GPS that is able to provide data via your phone or tablet’s operating system, we can typically receive that data like any other GPS-enabled app… On iOS, the Dual XGPS160 and Garmin GLO / GLO 2 are known to work this way, however the sample rate will typically be limited to 1 Hz due to iOS constraints. This data will appear and work the same as the Internal GPS, and it may be hard to tell the difference, but the actual quality and accuracy should be higher when the external GPS is connected. This is most noticeable when viewing your driving line plot, which should be much more accurate when compared to a session recorded with just the phone’s actual internal GPS.

A Note on GPS Lap Timing Accuracy & Sample Rate

There is a misconception that a 1 Hz GPS rate would limit timing accuracy to +/- 1 second. While that may be true for products that use crude timing triggers, this limitation does not apply to Lap Legend. We know your position, speed, and heading before and after crossing the timing line, and with a little bit of trigonometry we can reasonably calculate the precise time at which you crossed that line. As always, this depends on the GPS data that we do get to be accurate, which is much more important than sample rate.

It is true that a higher sample rate can further increase accuracy by giving us closer measurements and reducing the timespan that we have to cover with calculations, but that’s not as important as having reliable and accurate GPS data to begin with.

In many cases, it is possible to get lap times within 0.1 second of transponder times using just a smartphone’s internal 1 Hz GPS, when under good reception conditions and mounted properly (see advice in the Internal GPS section above). When upgrading to a quality external GPS, getting a good reliable signal tends to be easier, and the difference in timing can be as low as just a few milliseconds.

Adding Vehicle OBD and Sensor Data

Superior Motorsports Data via DauntlessOBD

We specialize in capturing vehicle data. One of Lap Legend’s market-leading features is the ability to use our DauntlessOBD dongle to obtain deep OBD data and far superior data sampling rates compared to many other apps.

Go deeper than the usual standardized OBD channels (RPM, Speed, Throttle, Temperatures, etc), with Extended channels on many supported vehicles, such as Steering Wheel Angle, Brake Pressure, Clutch, Tire Pressures, additional Temperatures, and more.

For maximum performance, you can enable Full Send Mode to blast data to the app as fast as possible, often achieving several hundred total data samples per second (depending on vehicle and channel configuration). This mode also further intelligently balances your wireless bandwidth to best serve high-priority data channels.

Available channels and performance can vary substantially by vehicle model and year, with most requiring a modern CAN-based vehicle (late-2000’s and newer).

Some notable examples with Extended data channels available are Chevrolet Corvette & Camaro, Ford Mustang, Dodge Challenger, Subaru BRZ & WRX, Toyota 86 / GR86 & GR Corolla, Porsche 981/982/991/992, and many other models from these manufacturers. We’re regularly working to expand our capabilities for even more vehicles, so be sure to update to the latest DauntlessOBD firmware for best results!

Alternatively, if you have our D-Shift Sequential Shift Light, you can connect it to capture your Engine RPM data and analyze your shift points.

3rd Party OBD Dongles / ELM327 Mode

As-is support for common ELM327-compatible OBD devices is available starting in version 1.6 as an add-on feature. Although DauntlessOBD offers many more data channels and far superior sampling rates, users coming from other apps who already had ELM327-style devices had asked us to support these. Due to performance and other considerations, there are limited data channels sampled in ELM327 mode.

Various BLE-based devices are supported on both iOS and Android, while Classic Bluetooth “SPP” devices are also supported on Android. Please note that not all devices will work, and WiFi and MFi modes are not supported. There’s a free trial period offered to give yours a try, with no commitment or payment info needed.

The device must have proper support of the ELM327 command set, and a compatible wireless communications implementation. Beware that the market is flooded with cheap “ELM327” clones that are known to be slow and/or unreliable. Those cause people quite a lot of headaches regardless of the app they choose, and that’s largely why this feature is a paid add-on, because we’re going to need a beer to deal with this.

If you’re in the market for an affordable quality OBD dongle for your mid-2000’s or newer vehicle, please consider DauntlessOBD, as it’s easily the best option for this app and can deliver a vastly superior experience and data set for you. The combined sample rate on a modern CAN-based car is often several times higher.

Viewing Your Recorded Sessions

Press the the “View Files” button on the main menu to access a list of your previous session recordings. This will show the track name, date/time, and a summary of each session. The icon is generated from your actual GPS data, so that you can easily see the course configuration for that session.

Tap on the session that you want to view and you’ll be taken to the Session Data screen which includes any notes you’ve entered, a list of statistics, your lap/run times, and you can scroll to the very bottom to find the Replay, Share, and Options buttons.

Each section has a collapse/expand button at its top right so that you can easily hide or show the sections you want. This button on the “Laps” section will give you the ability to cycle through 3 different visibility modes, so that you can choose how much detail is shown.

To view data and video for a lap, go to the lap you want in the Laps list and tap on the arrows on the right. Alternatively, you can view the entire session by pressing the “Replay” button at the very bottom.

Analyzing and Replaying Data and Video

Once you’ve opened a specific lap, or opened the entire session via the “Replay” button, you’ll have the ability to chart multiple data channels of your choice, view both top-down and 3D map renderings, compare against a reference lap, and watch your video.

• Use the buttons at top right of this screen control which displays are currently active.
• The gear icon at the top right of a display gives you access to choose it’s options, such as which data channel is displayed.
• Tap the expand icon at the bottom right of a display to go full screen.
• The lap buttons at the bottom right of this screen give you the ability to select the primary lap as well as a lap to compare it against, including laps from other sessions at this same track.

• When comparing two laps on the Chart display, it is useful to enable the “Plot by Distance” option, which will align the data based on the position on track.
• The “Delta Time vs Distance” Chart option is a great way to visualize where time is being gained or lost between the two laps you are comparing.

• Side-By-Side Video: When two laps are selected for comparison, and video is available from both, enabling the video display will automatically show video from both laps so that you can compare your laps visually.

Exporting Your Data and Video

Advanced Data Export Options: For deeper or advanced analysis, you can export your data into VBO, interpolated CSV, or non-Interpolated CSV formats.

In-App Video Export (with optional data overlays): Lap Legend includes the capability to share your session videos, or clips of selected laps, with or without data overlays. This can be accessed by pressing the Share icon on the video when viewing lap data, or via the “Share” button below the lap times on the screen before it. Please make sure your device has ample free space available when using this feature, and remain in the app with the screen on until it completes.

Export to External Video Software: You can also opt to export your raw video and CSV-formatted data for use with external software like RaceRender, or to view your data in a spreadsheet program like Excel. Open a session that you’ve recorded, scroll down below the lap times, and then use the “Share” button at to export your data into an Interpolated CSV format.

Raw Video File Access: Your raw video file (without data overlays) can also be accessed by using the “Share” button below the lap times, and then sending it to your computer either via another app (such as Google Drive) or by using USB File Sharing.

Other Tips: Another popular option is to use a screen recording app to record the app while playing back the data/map/video of your session or desired lap.