This article is not on selecting the best Harry's LapTimer edition. For more details on the Rookie, Petrolhead, GrandPrix editions, please check LapTimer's Products page.
Definition of major device classes
- Transponder and cable loop systems: Transponders are used in motorsport for lap timing purposes. A cable loop is dug into the race circuit near to the start/finish line. Each car has an active transponder with a unique ID code. When the racing car passes the start/finish line the lap time and the racing position is shown on the score board.
- GPS based lap timers and data recorders: This solutions will collect data continuously and not for dedicated spots only (like start / finish line). At a minimum, the sensors are installed in the car to collect and store data locally or distribute the data to an external unit. Most solutions will come with a complete in car solution providing both data collection and analysis options. Lap timing is done using track repositories or by offering some "self learning" modes.
Discussion on major device classes
From the definition the two general difference becomes clear immediately.
#1 While transponder systems are statically installed solutions, GPS solutions are more flexible and can be carried around.
#2 Transponder solutions focus on timing certain positions on track while GPS solutions record and analyze the complete drive of individual cars.
There is another difference not obvious immediately...
#3 Due to the technology used, transponder systems and GPS based systems differ in accuracy and reliability.
Pros and cons can be derived directly:
- From #1: Transponder systems (and cable loop based systems in particular) are good to handle for individual track organizers. Individual transponder tags are distributed to drivers participating, and the race can begin. Opposed to this, GPS based systems distribute the recording logic to individual cars adding more complexity to maintain the same service level for each car. On the other hand, they are easy to carry to the next track.
- From #2: Transponder systems deliver a very small set of data only, they focus on the result of the drive and not the drive itself. Most system will simply give you a set of lap times by participating car. Opposed to this, GPS based systems will deliver a very rich set of data along the track. This allows analysis of driving skills, reasons time is won or lost, and sophisticated functionality like predictive lap timing showing time won or lost at every position on track both while driving and during analysis.
- From #3: In an ideal world with GPS accuracy in the centimeter area, both the transponder and GPS solutions would deliver similar accuracy. Truth is centimeter accurate GPS devices require expensive ground based augmentation (GBAS) and a complex antenna architecture to cope with difficult receiving conditions. This type of solution is in the four or five digit dollar range (per car) and will lose some of the flexibility claimed in #1. Affordable GPS (or better: GNSS as GPS is one of several global positioning systems) solutions will be able to deliver accuracies around 0.02 seconds, while transponder systems will deliver accuracy of 0.001 seconds. On top of this, GPS accuracy will be disturbed by atmospheric disturbances temporarily, so individual measurements will be worse.
- To sum up the discussion on the major device classes, transponder systems are well suited for organizers, while GPS systems are superior for the driver and coaches. A timing accuracy of 0.02 seconds will by good enough very often. For serious competition, a transponder system (or even a doubled transponder system) will be mandatory. On the other hand, transponder systems add not a lot of help to improve driving, so GPS based systems will be mandatory for serious driving too. So for competitive racing, one will use a transponder systems. During training however, one will use a GPS based system. For amateur racers, or fun events, GPS based solutions can be used for both scenarios.
The remainder of this FAQ focusses on GPS solutions.
Definition of GPS data recording device classes
There is no "sharp" classification possible, many devices will be "cross border". We try a definition nevertheless to be able to derive pros and cons:
- Data recording boxes / Loggers: Pro level focussed, dedicated, and traditional solution installed permanently to an individual car. Includes pro level sensors made up from GPS, IMU (inertial measurement unit), and engine data. Engine data is collected using individual sensors wired into the car or using a direct car bus integration (CAN or OBD). Systems including video / audio solutions are available. Due to typical hardware development cycles, components are typically dated and solutions are very expensive (low volume, high investments necessary). Requires high installation efforts but works seamlessly afterwards. Limited or no real time information for the driver, analysis is done "after the fact" using some PC analysis tools. Examples: Racelogic's VBOX 3i / VBOX HD or Autosport Labs' RaceCapturePro/MK II
- All in one units: Dedicated devices offering both data recording and real time information in car. Amateur level focussed. Easy to install and handle. Limited analytics due to small screen size. For the same reason, functionality is limited and focussed on some characteristic numbers. Optimized but consumer level sensors built in - typically on the same level as versatile GPS or engine (OBD) adapters. Sensor range made up from GPS, IMU and engine data. Special devices available for motorbikes and karts. Most devices are "self learning" (i.e. do not have a track database) and are not connected to backend systems. Manufacturers of these devices need to make a difficult compromise between sensor / hardware quality, manufacturing costs, and development efforts. Other than for professional loggers, the sellable price is limited. Examples: Racelogic's Driftbox
- Lap timing apps: With the introduction of smartphones including some basic sensors around 10 years ago, this class evolved continuously and lead to a "consumerization" of data recording. Provided a smartphone is available, the solution can be purchased, installed and used directly on track at a very low price. Sensors used are the internal GPS, and IMU sensors. Besides this, video and audio is always available. The GPS sensor is the weak point as it is focussed on consumer level use cases like navigation. While it is o.k. for pure lap timing, it will have a too low resolution and accuracy for data analysis. Other than the dedicated devices listed above, lap timing apps benefit a lot from continuous research by large technology companies like Samsung or Apple. Functionality provided is beyond any other solution and heavily influences by modern connected technologies allowing sharing of data and results in real time. Examples: Harry's LapTimer
- Smartphone augmented systems: This is basically a combination of external sensors (including data recording boxes) and a lap timing app. It allows to compensate weaknesses of the smartphone's internal set of sensors and can be adopted as required (modular system). This allows high ratings for all criteria listed below - coming at a reasonable price. The main disadvantage of this solution is its complexity (external sensors are integrated using wireless technologies). While adding a single additional sensor like GPS is easy to accomplish, adding engine data and external action cams for 2nd and 3rd views can get a complicated set up to maintain. Examples: Harry's LapTimer plus Dual XGPS160 and/or GoPro HERO4 and/or OBDLink or ASL's RaceCapturePro/MK II
Rating for GPS data recording device classes
To allow an easy comparison, please find a rating for the various criteria and device classes discussed.
Code: Select all
Criteria / Device Class Boxes / Loggers All in one Smartphone App Augmented
sensor / data quality high medium low high
full cycle usability low high high high
functionality low low high high
installation efforts high low low high
reliability high high high medium
connectivity / networking low low high high
price very high high low medium
US$ 500-20000 US$ 500-2000 US$ 0-30 US$ 100-600