The requirements for small and medium scale topographic survey are not as stringent as those for geodetic survey. However, convenience and speed of operation are crucial.

Our solution here is to use a satellite based differential system (DGPS). This works in conjunction with a reference signal transmitted in the L1 microwave band. The choice of L1 is a compromise between precision and ionospheric disturbance.

The use of a DGPS provides suitable precision, but without the logistical restrictions of true differential operation.

Our chosen equipment is the LandStar DGPS from Racal which provides sub-metre RTCM accuracy.

For further information, please contact Geo Strategies at:
	Geo Strategies Ltd			Geo Strategies SA
	St John's Innovation Centre			Str G-ral V. Milea, 10A
	Cowley Road			Sibiu 550331
	Cambridge  CB4 0WS			Romania
	United Kingdom
	Tel:	+44 (0)1223 205080		Tel:	+40 (0)269 210832
	Fax:	+44 (0)1223 205081		Fax:	+40 (0)269 211165
	Email:	maps@geo-strategies.com		Email:	maps@geo.strategies.ro