GPS/GNSS is now a universal geographic positioning system. Its natural accuracy – within a few metres – makes it suitable for many applications destined for the general public, such as road navigation. Its navigation receivers (often GPS only) are inexpensive and are now built into low-cost applications for Smartphones and tablets.
Even greater precision is required for surveying and GIS (centimetric – our specialist field – or submetric), requiring the use of different means. We use:
- Trimble devices (Juno, 4700/4800 et 5700, R8 et GeoXR) with the addition of a total station if necessary.
- Trimble Business Center and GPS Pathfinder Office, post-processing software, RTKLIB freeware and various other GIS software (mainly Global Mapper and QGis).
- RTK methods using permanent national networks (Teria in France), or our own reference station installed nearby for greater internal accuracy if necessary.
- Post-processing differential methods (static and PPK), also using national networks (RGP in France) or our own reference station.
- PPP or RTX methods, which can advantageously be used to replace differential methods at some overseas construction sites.
Attachment to the official system (RGF93 and associated Lambert projections) is fairly simple in mainland France and some overseas territories, but rapidly gets more complicated elsewhere, when we have to juggle with:
- Old systems that are totally obsolete and incompatible with the quality of modern topographic devices and current needs.
- Other rather obsolete systems, requiring often-approximate transformation parameters.
- WGS84 and ITRF notions and their various applications over time and continent shifts, for countries having recently implemented a new geodetic system using GPS/GNSS methods.
Working examples of GPS/GNSS applications are available on this website: