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GPS stands for Global Positioning System. It is a series of satellites that circle the earth transmitting signals that allow one, through the use of a receiver, to determine their 3 dimensional location (latitude, longitude, altitude) anywhere on earth with a reasonably high degree of accuracy (usually within a few feet). GPS receivers are the basis for Car PC navigation using moving map displays and navigation software.
[edit] Requirements for GPS on a CarPC
Adding GPS to an existing Car PC requires two components:
[edit] Typical GPS Receivers
The vast majority of GPS units connect via either a serial port or USB cable. A growing number of GPS units are wireless and pair up with your computer via bluetooth technology. Bluetooth GPS units require you computer to have bluetooth transmission/reception capabilities. An additional category of GPS receivers are referred to as OEM GPS receivers. These receivers are Original Equipment Manufacturer receivers and are installed by the manufacturer of the automobile for use with in car navigation systems. Car PC builders can sometimes use an OEM receiver without the need for purchasing a separate unit. An additional type of unit is based on the Compact Flash or CF socket. These units are usually intended for use with PDA's.
[edit] Serial / USB Port
The GPS receiver often requires a a driver to be installed before the computer operating system will recognize it, enabling the navigation software to communicate with the receiver. The navigation software must then be configured to specify the type of receiver and protocol to use before it will function properly.
Some GPS receivers on Windows machines that connect via the USB port simply route the GPS information over to the serial port so the GPS appears to be a serial GPS. They do this by installing a small driver known as a USB-serial port bridge. In Windows, the user can then set the com port by right clicking My Computer-->Properties-->Device Manager. Look under the serial port entry and the serial port bridge should appear (if it installed correctly). Clicking on driver and then advanced allows the user to set the number of the com port to the desired port. Then that corresponding com port is entered into the configuration of the GPS in the navigation software and the receiver is ready to go.
On Apple / Macintosh machines, the Unix basis for OS X utilizes a similar GPS driver but there is no serial port. Most standard USB serial ports will work with a Mac if you have a serial GPS - follow the USB unit's instructions for installation. Or, instead, the output from the GPS unit is routed to a log file with a name such as /dev/tty/GPS12. When configuring the Mac for GPS, load the driver, plug in the GPS unit to the USB port and open the Network control panel in Preferences. If installed properly, you will be informed that a new serial port is available and that you must activate it. Select "Network Port Configurations" from the drop down menu and check the box to turn it on. Configure the GPS software using this port identification.
[edit] OEM (Original Equipment Manufacture) GPS Units
Many cars come with GPS antennas already installed in the car. It is possible to tap into an OEM antenna and use it for your car PC. These involve a separate GPS module that have an external antenna.
These have the advantage of having a external waterproof antenna and the modules are quite often better at obtaining locks.
A little bit of electronics work might be needed to convert the TTL output to serial level and to provide a battery backup and power to the receiver.
[edit] Compact Flash (CF) Receivers
There are also CF type receivers that can plug into your PDA's Compact Flash slot, or your PC's PCMCIA slot with an adapter. CF is same as PCMCIA only smaller. They can come with an external waterproof antenna. Some have observed that a PDA seems to gets a lock much much faster than the PC with a CF GPS in it.
Please help expand this topic.
Deciding which unit is best is a subjective choice. In general, users asking this question are usually trying to avoid GPS units with unacceptable performance rather than trying to buy the absolute best GPS unit. Nearly all of the GPS receivers work reasonably well. The main differences between GPS units are associated with the amount of time it takes to determine a fix from available satellites, the accuracy of the position fix, and the sensitivity of the GPS receiver. Other factors to consider are the ability to log where you've been, the ability to download route data from the receiver (generally a feature of all-in-one handheld units), and form factor. Many users have reported great success with the Rikaline and BU-303 models.
There are some features which can affect accuracy or might be desirable. WAAS stands for "Wide Area Augmentation System" and will provide a more accurate fix than one without this feature. Some devices are receivers only without displays so will require a connection with your computer, however they typically can be mounted outside so have a better view of the GPS satellites. If you want to "take it with you" you will need one with a display. Some include maps onboard, some require them be downloaded from a PC. If you have a map-capable GPS and plan on traveling outside the USA (even Canada or Mexico), you might want to check if such maps are available. Some units have no external interface, but if you just want a stand-alone navigation unit they might be better than one that can talk to your PC. Most GPS units update once per second. Garmin and others make 5Hz (updates 5 times per second) GPS modules which increase precision and update speed of tracking.
A thread that compares recievers side by side
This GPS Software Comparison Chart gives a good overview of the capabilities of popular GPS Software
A poll of the 'best' navigation software for Windows
Macintosh native OSX navigation software:
Opensource navigation software :
GPS Splitter
[edit] Common Problems with GPS on a Car PC
Problem: When plugging in the GPS to the serial port, the mouse starts running all over the screen, randomly clicking things! Answer: The operating system has mistaken the GPS for a serial mouse. Disable the serial mouse (normally in the device manager - don't delete it, set it to disabled).
Problem: I want to use it to feed more than one application simultaneously. Is that possible? Answer: Yes. GPS is addicting and once you start being able to pinpoint your location, you start to collect applications that do various things with GPS and require simultaneous access to your unit. Unfortunately, if your GPS is serial, you can't share the com port between two applications like iGuidance and Netstumbler. Fortunately, there are a few solutions for this.
- Some Bluetooth receivers permit more than one connection at a time.
- GPSgate is a commercial application that allows you to share your ports with more than one application. It has a 14 day trial download.
- Xport by our very own member Curiosity, also allows you to share access to your GPS.
- GPSD can act as a server to GPS applications, allowing more than one application to read from the GPS data stream at a time. Unfortunately, each application that needs GPS information must be GPSD aware or you need to use virtual serial ports such as the one from HW, and you may need to send the "R" character to the virtual serial port pointed to gpsd (typically 127.0.0.1, port 2947) to turn on the "Raw" NMEA data stream, but this can be done in a command window with "ECHO R >COMxx".
