from: Zlinszky András <zlinszky.andras@okologia.mta.hu>
to: Mick West <mick@mickwest.com>
date: Mon, Sep 12, 2016 at 4:23 AM
[...]
As first author of the publication "Observation of a local gravity potential isosurface by airborne LIDAR of Lake Balaton, Hungary", published in Solid Earth 5 355-369, 2014, I clarify the following:
with the statement "As far as the resolution of the geoid model allowed, the close correlation of the two data systems confirmed that standing water has a truly level surface" we do NOT state that the water surface would be planar or "flat". This means that it is "level" in terms of following a gravity potential isosurface at a constant orthometric height above the geoid. The geoid is a curved surface, resembling an ellipsoid but with considerable deviations from rotational symmetry ("geoid undulation"). Only over a very small surface can this be approximated as flat. The surface of the lake in our survey was confirmed to be close to hydrological equilibrium, that is, to closely follow the local curve of the geoid. Fig. 2 a of this paper shows how the water surface height deviates from the WGS 84 ellipsoid, it is by no means planar.
I am not in collaboration with Sándor Székely, nor has he ever contacted me. In the cited paper, we have a co-author, dr. Balázs Székely, who is NOT to be confused with Sándor Székely.
Best regards,
András Zlinszky