Differential GPS (DGPS) Products	How the differential beacon, radio and satellite services (DGPS) and WAAS, aid mariners, shipping, and even surveyors and farmers.	The AMSA beacon signal which is active over the length of the Queensland coast, and also in the Sydney, Melbourne, Adelaide, Perth, Darwin and Port Hedland (WA) areas is a boon to many users of positioning equipment. The idea of the beacon system, is to provide GPS with correctional signals, to negate some of the errors native to GPS. AMSA, as the Australian authority for shipping safety, has invested a considerable amount of money on this facility. You get the signal free, even inland for hundreds of kilometres. Better accuracy is obtained using a suitable receiver for the GPS unit of your choice. Check the latest DGPS prices,
Accuracies? Well the beacon receiver can certainly make a difference. Typically with a single GPS receiver of any type (whether it is $200, or $20,000) you will be getting errors of 10 to 15 metres in absolute terms. With a beacon receiver, this will reduce to say 1 to 5 metres, If you have averaging, and record over a period of time, accuracy will also improve.	Users?. Mariners who need better accuracy negotiating seaways and entrances. Geologists, surveyors, scientists on botanical and geographical projects, technical officers in local government, and police forensic people, all need accuracies down to 1 metre where possible. Again Johnny Appleseed GPS can be your supplier of choice, because we know and speak GPS.	GPS Products Index   Home Page  Software to suit GPS   Prices and Catalog

Garmin users can obtain differential solutions using the following CSI-Wireless system, or a Thales beacon-on-a-belt system. 1. CSI-Wireless Differential Beacon Receivers CSI supply systems for use in a vehicle or boat, and we can supply a complete back-pack system for field use (Backpack). 2. Thales Beacon on a belt Thales Mobile Mapper Beacon to work with some Garmin GPS. This achieves consistent accuracies of 2-3 metres, rather than a 5 -15 metre solution. Furuno, Model GP37, uses the AMSA beacon, ideal for boats.	Leica and Thales solutions Thales Mobile Mapper beacon on a belt system will improve accuracy fo some Garmin serial GPS. JRC combined GPS and beacon, outputs standard NMEA serial data, corrected to 2-3 metres. Can work with handheld and laptop computers. Leica GS5- for AMSA beacon reception, and true mapping capability. Ideal for Arcview and Mapinfo users. Ideal for Compaq iPaq PDA and Windows CE or PocketPC2002 and 2003. For all sorts of 2-3 metre mapping. Leica GS20- the new Bluetooth enabled handheld with graphical screen, and belt batteries. Very quick and effortless mapping in the field, to sub-metre level. The GS20 can be used with free AMSA beacon, or the Omnistar satellite DGPS signal (see next column on Omnistar). Leica MXMarine - specialized marine, mining and industrial DGPS for accurate position. Index for Leica DGPS solutions	Omnistar DGPS systems use correction signals transmitted by satellite. This means you get an Australia or South East Asia wide coverage. The unit is connected to your own computer/PDA, or a Garmin hand-held, or is incorporated in the Leica DGPS backpack survey system. Omnistar and Nomad PDA DGPS field data package, ready to go. OmniSTAR is a high performance DGPS positioning service for land and air applications. The system is characterised by the portability of its receiving equipment, suitable for vehicle mounting or 'backpack' use. The OmniSTAR system offers superior geographical coverage compared with competing systems. Hemisphere unit can use optional free-to-air or Omnistar DGPS data. For Marine use, we can supply an economical Furuno, Model GP37, which uses the AMSA beacon, and is accurate to 2-3 metres. Please phone our Salisbury office on 07 3717 8555 for more information.

Some of the new Garmin receivers are WAAS capable. WAAS capable receivers do not require addition of any external DGPS device. Unfortunately, this feature does not work in Australia. Look for this symbol. US Aviation authorities have been experimenting with LAAN, which is a localised version of WAAS. This will give better than metre accuracies, and will enable precision instrument approaches and landings.

WAAS- Wide Area Augmentation System As you know, position on earth is calculated by triangulation of intersecting radio signals at the GPS receiver. The signals emanate from earth orbiting satellites of the US Defence Department GPS constellation. It is possible to "augment" these signals from other satellites or ground transmitters of known position, thereby increasing either reliability, or accuracy, or both. WAAS is currently available over US, some northern Pacific areas, and Europe (EGNOS). WAAS is still in Beta (test) mode. WAAS does NOT work in Australia.

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