[FOSS-GPS] Rtklib Why do I require a base station

[antongstrydom]

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




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