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GPS modules, their description and use PDF Print E-mail
Written by Jurij Mikeln   

The abbreviation GPS is known to virtually all of us. Amongst those who have an electronics background, it’s been known for many years. Within the general public it’s only been common knowledge for the last 10 years due to the existence of low-cost GPS devices and smart phones with GPS built in. In this chapter, I will introduce to you two GPS modules that are representative of the GPS market. Also, I’ll show you some Bascom examples and other interesting programs. GPS modules came to my attention a few years ago, when our company purchased a few GPS01 modules from HopeRF [1]. A few weeks later, we purchased another GPS module, the FGPMMOPA6B by Global Top [2]. They differ one from each other by the chipset that is used. The GPS01 is based on the Skytraq Venus6 chipset while the FGPMMOPA6B is based upon the Mediatek MT3329 chipset.

To the average GPS user, which module you use doesn’t make much difference, as both modules work well. Technical details matter to those of us who want to include these modules in our devices. For everyday use, we need a GPS location update every second, while for advanced use, such as for airplane navigation, we need location updates every 1/10th of a second. To achieve this, we have to set our GPS module accordingly. This, and much more will be covered in this chapter.

All those abbreviations

First, let me explain a common delusion held by some novice GPS users: when they ask me how strong the GPS transmitter is. A GPS module never transmits signals - it only receives them from the GPS satellites! For that, it only needs open sky.

There are many abbreviations within the GPS world. Let me start with the abbreviation GPS, which stands for Global Positioning System, which is well-known. Then we have NMEA, WAAS, HDOP and many others, which may not be known by everyone. I will introduce you to some of the most common ones:

  • NMEA stands for National Marine Electronics Association. GPS modules can communicate with the host system (or microcontroller) in binary or via the NMEA01823 protocol. All GPS devices that are sold in volume use the NMEA protocol. In most GPS modules, the output protocol can be set during programming.

  • WAAS stands for Wide Area Augmentation System, which consists of approximately 25 reference stations (called Wide Area Augmentation System Stations) that receive the GPS signal on the ground. These stations analyze those GPS signals and send corrected data to geostationary Inmarsat satellites, which send this data back to Earth on the GPS L1 frequency. WAAS signals are received by our GPS module. In Europe, you can receive WAAS satellites No. 33, 37 and 44, while in the USA satellites No. 35 & 47 can be received. There are places on the internet to look if you would like to know more about this subject [3].
  • SBAS stands for Satellite-Based Augmentation System. Several countries have implemented their own satellite-based augmentation systems. Europe has the European Geostationary Navigation Overlay Service (EGNOS) which covers Western Europe and beyond. USA has its Wide Area Augmentation System (WAAS). Japan is covered by its Multi-functional Satellite Augmentation System (MSAS). India has launched its own SBAS programme named GPS and GEO Augmented Navigation (GAGAN) to cover the Indian subcontinent. SBAS systems are essential for applications where accuracy and integrity are critical. In particular, they are indispensable for all applications where people’s lives are at stake or for which some form of legal or commercial guarantee is required.
  • For example, SBAS make it possible to improve and extend the scope of GPS applications in areas such as precision farming, the guidance of agricultural machinery, on-road vehicle fleet management, and oil exploration (for the positioning of platforms at sea) or for scientific applications such as geodesy (source [4].
  • EGNOS stands for European GEO-.stationary Navigation Overlay System which is satellite supported system to improve GPS and GLONASS navigation systems. Earth stations receive GPS signals and send a correction factor via geostationary satellites to users. With these correction factors, an accuracy of 1.5 meters can be achieved.
  • GLONASS is the Russian version of GPS system...

GPS modules, their description and use

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Last Updated on Tuesday, 28 August 2012 10:12
 
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