CMS Lap Timer Pro

The Cantrell Motorsports Lap Timer Pro is the easiest to use GPS-based lap timer, data recorder, video recorder, and performance analysis app available.

Main Features


Overview of Operation

Tasks (screens) are selected using the botton corner buttons.

The Recorder is used to record data & video. Recorded data is saved to Runs. Videos are saved in Pictures.

Runs is used to organize data runs and to display summary information for each run.

Analysis is used to analyze & compare data in Runs.

Video is used to view recorded videos with data overlaid on the video. Video is also used to export video with data overlays to the Pictures. Videos consume approximately 1GB of device storage per 12 minutes. Use the Recorder screen to check the available storage before starting a session; otherwise, video may not be recorded. Minimum recommended for a 20 minute session is 4GB.

Settings is used to enter information such as the driver name, car name, location name and to set various app preferences.

Locations is used to view lap times using the CMS Cloud Service.

Help is used to display the user guide and access Support information.

External GPS Modules

Due to limitations of the built-in GPS, the data may suffer from inaccuracy. Use of the built-in GPS is intended for demonstration purposes only and will generally provide useful data only at relatively slower speeds.

An external GPS module is required for high speeds.

Recommended External GPS Modules

GPS Module Notes
Dual XGPS150A Bluetooth GPS 4Hz update rate (requires firmware update)
Dual XGPS160 Bluetooth GPS 10Hz update rate
Qstarz BT-Q818XT Bluetooth GPS 10Hz update rate. Programmable for 5Hz also.


Mounting the Device in the Vehicle

Mount the device securely.

The device or GPS module must be mounted with a clear view of the sky so that it can receive a strong GPS signal; somewhere on the dash or windshield are good positions.

The device may be positioned vertically or horizontally. It should be reasonably level horizontally and vertically, and face toward the back of the vehicle. If you do not need to see the screen, the device may also be mounted flat; screen facing up and top facing the front of the vehicle.

To obtain the best possible data, the device mounting position is important since the built-in accelerometers are used to collect lateral and longitudinal G forces. The LatG and LongG displayed on the Recorder screen should both be close to zero.

When using an external GPS module, it is possible to ignore the device's orientation; it can be kept in a pocket or glove box for example. In this case, use the automatically calculated GPS lateral and longitudinal G forces in Analysis.

Recommended Mounts

Mount Notes
RAM Mount Universal X-Grip Suction Cup Mount

Universal mount.

A hard case that protects the side buttons from being pressed by the X-Grip is recommended.