Introduction
Global Navigation Satellite Systems (GNSS) are used to determine a position on earth and to receive a
globally valid time signal.
The general term for satellite navigation is GNSS but the term GPS (Global Positioning System) has
become a synonym for this technology, but GPS is only one of the four GNSS.
Besides GPS, there are the satellites systems called GLONASS (Russian Federation), Galileo (Europe)
and BeiDou (China).
The more satellites are used to determine the position, the more accurate and stable the determination
of the position and thus the determination of the speed.
For more information on the theory and exact functionality of GNSS positioning, we recommend the u-blox GPS-Compendium book.
Via positioning capabilities of GNSS, all 2D GPS/GNSS modules can be used for lap time and GAP time calculations!
SIO & GPS/GNSS2CAN
2D serial GPS/GNSS receiver (Mouse) can be connected to 2D loggers supplying serial connection (SIO).
The GPS/GNSS2CAN receivers can be connected to all 2D system via CAN bus.
For serial data transmission, the GPS/GNSS serial antenna must be connected directly to the 2D recording device at the appropriate serial port using a four-pin connector, whereas a GPS/GNSS2CAN module can be connected at any point in the 2D CAN bus system.
Please see the GPS/GNSS General description with an overview of advantages/disadvantages of SIO & GPS/GNSS2cAN modules.
Sampling Rates
Until summer 2021 2D offers single GNSS modules based on GPS only with maximum 12 concurrent satellites with sampling rates 10, 12.5 and 50 Hz.
From 2021, new 10 and 25 Hz GPS/GNSS modules are additionally available as serial and CAN modules, which using up to 32 GNSS satellites what significantly improves positional accuracy!
For acceleration and braking tests with vehicles we strongly recommend using the 25 Hz module.
In addition, this module is very well suited for all kinds of fast outdoor sports such as skiing, where a combination of high dynamical capabilities and good positioning accuracy are required.
Click here to download an overview about 2D GPS/GNSS modules.
Click here to download a document with many important information regarding dynamics of GPS/GNSS modules with different sampling rates.
Mounting
In general, the correct mounting of GNSS modules must be observed in order to obtain a usable measurement result.
Basically, the output, raw speed of the GPS/GNSS module is a result of the current vehicle speed, the speed of movement of the vehicle due to e.g., pitching movements when braking and the speed caused by inherent movements of the GPS/GNSS module due to poor installation.
The latter can be caused by vibrations of the poorly mounted module or incorrect values caused by the speed of the GNSS module’s own movement e.g., due to the tilting movement of the module during heavy braking.
It is very important that the GPS/GNSS module must have clear view to the sky to get the best possible GPS/GNSS satellite reception!
It is recommended that the module be mounted evenly on a solid metal plate using high quality double-sided tape at a location on the vehicle that is not shielded from other parts of the vehicle.
Thereby three advantages are gained:
- A metal plate or carbon fibre parts are acting as an “amplifier” and strongly improves the GPS/GNSS signal reception. If no metal plate or carbon fibre is used as mounting base, a self-adhesive ground plane for GPS modules (AC-GPS_ground_plane-000) must be used
- Much better mounting possibilities are achieved when using a metal plate because the antenna can be mounted even and fix on the plate with double-sided adhesive tape to reduce movements of the antenna itself
- By fixed mounting on plate the mass of the antenna is increased and thereby the impact of external vibrations on GPS-chip is greatly decreased
For more information about mounting GPS/GNSS modules please click here to download GPS/GNSS general description.