Hello all. I have been reading quite a bit on the forum regarding RTK with Emlid Reach RS+, but I am encountering a discrepancy for which I cannot find a proper explanation. Maybe someone can help.

I used 2 Reach RS+ in a base-rover configuration to collect RTK points. Before starting the survey, I calculated the base position with a 10-minutes average, noting down coordinates.

The position recorded in the RTCM3 file matches the one I noted down within 0.04mm in X,Y,Z.

The base position obtained from the 10-minutes average is:

**Lat: -46.558107459851804**

**Lon: -67.43280756912664**

**BaseHeight: 34.053**

**Base Antenna Height: 1.305**

After averaging the base coordinates, I started the RTK survey. The first point I collected is the base position itself (just in case, I thought).

The position I have out of the Rover is:

**Lat=-46.5581079411258**

**Lon=-67.4328064124377**

**RoverHeight=33.850**

**Rover Antenna Height: 1.775**

By making some calculation, it turns out that the XY distance between these two points is around 10 cm, which is OK as I did not put exactly my rover above the base (that is in my field notes).

What leaves me a bit more puzzled is the height. If I understood correctly how data is stored by EMLID, then I should calculate the height of the point on the ground with the following procedure:

PtgroundBase=BaseHeight-Base Antenna Height=34.053-1.305=32.748m

PtgroundRover=RoverHeight-Rover Antenna Height=33.850-1.775=32.075m

So, while the two altitudes should be virtually the same, I have a difference of 0.67m between them. The pole heights are OK, I re-checked them.

Any hints you can share?