General FAQ GPS

[Stevie]

Does the GPS receiver have to be outside the car?

This is a very common question, it really all depends on what car you have. Most recent models of cars are being fitted with heat reflective windscreens, this causes problems for GPS systems as it can cause the GPS signal to be lost. This is due to very very small wires running through the glass this then stops the signal from the satalites going to the receiver.

It can be cured by using a Reradiating antenna, which can be found http://www.totalpda.co.uk/product4481_0.aspx

Information
Give your GPS signal a boost by installing this product on the outside of your car. The RA-45 reradiating antenna increases your GPS signal. If you drive a car that has a heat reflective windscreen then this product is essential for the operation of your Satellite Navigation System.
You simply place the antenna at a point in your car where a signal can be received, then trail the cable so it is close to your original GPS receiver. It needs to be powered from your 12V accessory socket, but is carries a pass-through connector so you can have two devices powered at the same time.

What receivers are available?

You can get all different types of GPS receiver from:

Cabled receivers
Sleeve based receivers
IR enabled receivers
Bluetooth enabled receivers


Can i go off road with my GPS?

Yes your GPS receiver will work anywhere it is the map data that you would require. Most of the civilian based systems are designed for road use. You can however get different software and map data to cover everything from off road maps, marine and aviation.

What is NMEA?

NMEA stands for National Marine Electronics Association
National Maritime Electronic Association. The NMEA 0183 standard for interfacing marine electronic devices is a voluntary industry standard, first released in March of 1983

What is meant by TTFF?

TTFF simply means Time To First Fix
This is the time it take for the receiver to obtain a satellite position from at least three satellites. Most receivers will work allot better if they get four more as if you loose one satellite you still have a fix with at least three.

What is SiRF

SiRF is a company that manufacture chipsets that are used with GPS. The chipsets have improved over time and the most significant improvement has been with SiRFstarIII. The available SiRF chipsets are:

SiRFstarIII
SiRFstarIIe/LP
SiRFstarIIt
SiRFstarIIA


SiRFstarIII

Achieving TTFF of 1 second and acquiring down to -159dBm, SiRFstarIII is designed to meet the demands of wireless and handheld LBS applications.

With its rapid time-to-first-fix and high sensitivity, the SiRFstarIII architecture is designed to meet the rigorous demands of wireless and handheld LBS applications, and provides superior location performance, both indoors and out, for 2G, 2.5G, 3G asynchronous networks.

The SiRFstarIII architecture packs a performance punch, achieving time-to-first-fix of one second for aided starts in outdoor GSM environments and acquiring signals down to -159 dBm. This makes real-time navigation practical, including in many indoor environments, through urban canyons, and under dense foliage. Unlike the lengthy sequential search process of traditional GPS architectures, the SiRFstarIII architecture, with the equivalent of more than 200,000 correlators, enables fast and deep GPS signal search capabilities, resulting in significant improvement over today’s architectures that contain a few hundred to a few thousand correlators.

The SiRFstarIII family is comprised of the GRF3w RF IC, the GSP3f digital section, and the GSW3 software that is API compatible with GSW2 and SiRFLoc.


SiRFstarIIe/LP

If you’re manufacturing or designing a device using GPS with battery power, the SiRFstarIIe/LP provides an innovative way to add location awareness to your product. Drawing only 60mA in full power and 20mA in TricklePower, the SiRFstarIIe/LP is one of the lowest power full-feature GPS chipsets on the market. The chipset also has an ARM CPU with 40 MIPS of total processing power. This can be used as the engine to drive your product reducing component cost by removing the extra CPU.

The SiRFstarIIe/LP family is comprised of the GRF2i/LP low-power front end, the GSP2e/LP highly integrated digital section, and the GSW2 software, which provides a path for new features and continuous GPS improvement.


SiRFstarIIt


SiRFstarIIt makes it easy and economical to add high-performance SiRFstarII technology to systems that are based on many popular processors and operating systems. The SiRFstarIIt solution allows GPS function to be added at minimal cost in components and circuit board area, by sharing the host system's processor and memory resources. The chip set acquires and tracks satellites, then sends raw measurements to the host processor running the SiRFNav software in parallel with the host applications. The SiRFNav software module computes position time and velocity. For enhanced accuracy and navigation reliability, WAAS corrections can be applied to GPS measurements or GPS can be combined with dead reckoning data and processed by SiRFDRive software.

The chip set consists of the GSP2t highly integrated digital chip, GRF2i integrated RF receiver and the SiRFNav software. The two chips are packaged as 9mm 48-pin LQFP packages and require minimal external components thanks to their high level of integration. SiRFNav software is designed for easy porting to host systems.

SiRFstarIIA

The SiRFstarIIA is designed for applications that will benefit from the high performance of SiRF GPS incorporated into a System On Chip that provides system processing and peripheral control and interfaces. The GSP2A provides over 65 MIPS of throughput and is capable of providing all the central processing for many applications. Interfaces include UARTS, vehicle CAN buses, USB, SPI and ATAPI/EIDE. It can also interface to control panels and display units and support audio interfaces for entertainment or voice prompts.

This power and flexibility makes the SiRFstarIIA an ideal central component for automotive telematics products, including emergency and concierge services, road-tolling, security, and low cost navigation and infotainment systems.

The optional SiRFDRive closely coupled dead reckoning system uses in-expensive heading and speed sensors to provide reliable positions in challenging signal environments including urban canyons, tunnels and under foliage. The GPS and dead reckoning measurements are used in the navigation filter to validate and calibrate each other ensuring accurate and continuous navigation in all conditions.”

All information on the SiRF chipsets are available from http://www.sirf.com/