GPS Applications
Primary Survey control
All surveys undertaken by the Discovery Programme are required to be compatible with the OSi Irish Grid*. This is to ensure full integration of all data sources in GIS. The Trimble 5800 receiver, using the VRSNOW correction system, offers a reliable, consistent and efficient solution to achieving primary control.
* A more accurate, consistent and GPS compatible national grid called Irish Transverse Mercator (ITM) has been introduced and is available directly from the VRSNOW GPS system. Future projects will require data to be gathered in this grid system.
Secondary Survey Control
Secondary control points can be achieved using the Trimble 5700 base and rover system, with the base station set up over a primary survey control point established as described above. Alternatively the Trimble 5800 system can be used to establish further points as done for primary control. The availability of GPRS mobile phone signals may determine which method is most appropriate.
Setting-out Grids
Geophysical survey grids and excavation trenches require ground pegs to be established in pre-determined Irish Grid positions. This can be achieved using the Trimble 5800 VRSNOW system, or if many points are required the 5800 is used to establish absolute control in the general location, the base station set-up at this location, and RTK survey using either the 5700 or 5800 used to set out the points. (Lengthy phone connections have to be avoided for cost reasons)
3D topographic surveys
RTK survey is the most efficient ground survey method for gathering survey data for constructing 3D models. Either (or both) the 5700 and 5800 receivers can be used in conjunction with the base receiver.
Survey Plans / Excavation features and finds positioning
RTK survey (5700 and/or 5800) in conjunction with the base is one option for this survey application. Alternatives, such as total station, may be more attractive as the equipment could be tied to a site for long periods, unavailable for other tasks.
Reconnaissance
The hand-held Garmin 12 receivers provide an excellent cheap solution to locating features in the general landscape.
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