Hi David It is really very simple, the base is fixed and the rover is moving. In GPS terms both have an error however in close proximity the error (fault) on both units are basically equal.
The base transmits error correction data to the rover and by doing this it allows the rover to do the mathematics to correct the error and place both units much more accurately now placing them both in a position depending on the correction anything from whatever to about a centimeter of the true position. This is in the WG84 system, there are however a multitude of systems but basically two systems that are used for flattening the earth (remember you are standing on a ball and therefor all measurements are strictly speaking angular measurements that have to be adapted for purposes of measuring "flat" distances.) To do theses transformation we use UTM or Transverse Mercator to relate to a flat measurement The maths for doing this is called RTK and is rather complex. You if I remember correctly are using a L1 GPS receiver RTK is therefor limited to a base line of around 10km. If you can connect to Ntrip and you are not further than 10km away and use the NTRIP station as a base. We use VRS to do this as we have a number of L1/L2 base stations that relay all their individual RTCM messages to a single computer where our rovers connect to, the program will calculate the closest virtual point to the rover and transmit correction using this point and the combined information from all the base stations. I can carry on all day but the long and short of the story is that without a base you cannot do RTK and therefor your rover cannot calculate it precise position I trust this answers your question Regards Anton -- View this message in context: http://open-source-gps-related-discussion-and-support.1099874.n2.nabble.com/Rtklib-Why-do-I-require-a-base-station-tp7572960p7572962.html Sent from the Open Source GPS-related discussion and support mailing list archive at Nabble.com. _______________________________________________ This message is sent to you from [email protected] mailing list. Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your subscription For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS
