All the above navigators were tested through the M5 tunnel to see how they react when the signal drops out.
All the navigators tested failed the test with all the signals dropping out in under 30 seconds of entering the tunnel. However, two of the latest navigators were obtained near the completion of this thesis in order to test and see how they operate under the tunnel using a new technology called Enhanced Positioning Technology (EPT).
These navigators are the Navigon and TomTom GO930. These were only tested under the tunnel and a full analysis will not be carried out since they were acquired really late. They will be used to demonstrate how GPS navigation technology is advancing over time.
Enhanced Positioning Technology (EPT) is a new technology used by TomTom and Navigon that allows a driver’s current position to be estimated when GPS reception is low or unavailable. This technology is mainly developed for tunnels and car parks. In this instance, the EPT allows for navigation to continue rather than just stop operating like other navigators. (TomTom, 2008)
At the beginning of a journey it takes about one minute for EPT to fully calibrate. Once the device is docked in the car, with good GPS reception and at a standstill, it calibrates for five seconds. Then, for one minute after setting off, the calibration engine collects data from the sensors. (TomTom, 2008)
For the EPT to work, an accelerometer and a gyro is fitted into the GPS navigator. The accelerometer calculates the acceleration and change of speed in the car whereas the gyro calculates any changes in direction. The data received from sensors is then matched against data off the map allowing for the position to be estimated. (TomTom, 2008)
The TomTom navigator was put to the test. There is no GPS signals received by the navigator and this can be seen in the bottom right corner of the navigator with none of the five bars showing any reception.
However, the navigator is still operating with distance changing as you travel. It will remain doing this for the entire trip under the tunnel until the driver exits the tunnel in which normal satellite reception will then be received.
The Navigon was really impressive in its performance in the tunnel. Not only does it operate in the same manner as the TomTom through the use of the EPT, but if the driver needs to take an exit within the tunnel, the screen changes from a simple 2D view common to all navigators into a “street view” clearly defining the exit the driver should take.
The only issue with these navigators using the EPT technology is that if the exit is not taken and you continue travelling straight then it will assume you have taken the exit and may not realise it until you have exited the tunnel.
TomTom’s New Live Traffic Update- How does it work?
TomTom’s new live traffic update on its navigators requires a traffic module connection iin order to operate. This backbone of this module connection and the live traffic updates is not TomTom itself, but a company called Intelematics Australia. (SUNA Traffic Channel, 2007)
Intelematics Australia has developed this channel for live traffic updates known as the SUNA Traffic Channel (SUNA Traffic Channel, 2007). At the moment, TomTom is the only company to have made an agreement to use this channel for their navigators.
The SUNA Traffic Channel provides the connection from navigators to real-time traffic information. It provides the navigator with the following information (SUNA Traffic Channel, 2007):• How long a delay will be?
• Whether the driver should detour?
• Time of arrival
• What is the cause of the traffic jam?
The basis of the SUNA traffic channel is the traffic and road data that it provides that allows drivers to be informed with better information and provide greater ease while travelling. In particular, it has made it easier for delivery companies to predict time of arrival of products with the use of such a service (SUNA Traffic Channel, 2007).
The global standard for Australian Traffic is the Traffic Message Channel (TMC) in which the SUNA traffic channel is built to conform to. There are two features that make up the SUNA traffic Channel, these are (SUNA Traffic Channel, 2007):• The Suna Traffic Channel Content • The Suna Traffic Channel Access method
The Suna Traffic Channel Content consists of information that includes both travel speed and incident data for each road. This information is based on data collected from traffic light systems that measure traffic congestion as well as investigate vehicles and any related traffic jams. The congestion information is collected from intersections across the country which provides continuously updated images of traffic conditions (SUNA Traffic Channel, 2007).
The SUNA traffic channel broadcasts using a Radio Data System (RDS). The RDS-TMC connection is the technology that allows navigators to receive real-time traffic information. This is carried out with the RDS-TMC coding the SUNA Traffic Channel information onto an existing FM broadcast service. This is then received by the navigator allowing it to identify and avoid any possible traffic (SUNA Traffic Channel, 2007).
The SUNA traffic information is also available in XML format. XML-TMC supports GPRS delivery to navigators, the internet and wireless applications. Therefore many mapping services have been designed to include this XML-TMC feed as a standard feature allowing for the simple and fast integration of the SUNA Traffic Channel (SUNA Traffic Channel, 2007).
It was expected that the TomTom would achieve the fastest TTFF. This is due to the fact that TomTom is the first to develop a software application called TomTom QuickGPSFix. It is the only navigator from all the navigators tested that implements such an application. (TomTom, 2008)
Generally, every GPS satellite will broadcast a signal approximately every 30 seconds Waiting this long can be a real nuisance to users and can sometimes take longer to get a fix on the satellites if surrounded by high-rise buildings or trees that weaken the signal. In particular, if a navigator has not been turned on for more than a day, it will ad to the difficulty of obtaining a fix. Through the QuickGPSfix application, it consists of a set of algorithms that predicts where the GPS satellites will be positioned for the next 7 days. This then allows the TomTom navigator to calculate the position rapidly, even when a signal has been weakened (TomTom, 2008).
This is simply carried out by connecting the TomTom navigator to a PC or accessing it via a wireless mobile phone connection allowing the TomTom navigator to connect to TomTom’s software application, TomTom HOME. This is free and will provide QuickGPSfix information to TomTom users automatically. It is recommended that updates are carried out once a week (TomTom, 2008).
WHAT SURROUNDING ENVIRONMENT IMPACTS GPS NAVIGATION?
A 3D model of the Sydney CBD was obtained in order to show what kind of surrounding environment has a major impact on GPS car navigation.
Through our tests, a local area with no high rise buildings had no impact on any of the navigators since there was a clear view of the sky. However, in the Sydney CBD, which contains all high rise buildings, there was a major effect on the navigator’s satellite reception.
This is due to the fact that there is a limited clear view of the sky and therefore satellite signals are either unable to be received by the navigator because buildings are impeding the path, or signals may bounce off the high rise buildings or other structures.
As observed in the following images and video, driving through streets such as Clarence St, York St, George St and Carrington St, the surrounding environment consists of high rise buildings and structures along with high spread trees, all in which impede a satellite signal being received from a navigator.