I'm looking at some computer code that purports to compute the correction for the earth's rotation involving two earth stations (A and B) that are collecting meteor data. The closest reference I can offer that talks about this is by Whipple and Jacchia, Reduction Methods for Photographic Meteor Trails, 1956. It's available on a pdf at <http://www.sil.si.edu/smithsoniancontributions/Astrophysics/pdf_hi/SCAS-0002.pdf>. [Broken] I'm just trying to get some basic understanding of what's going on. The section involved is "Computation of orbital elements". The corrected velocity involves V∞ and Vc, magnitudes. and equations (81) and (82). (82) is somewhat familiar from a post I made several days on "Position and velocity vector of point referred to the equinox". V∞ in understandable as explained by the use of (46) and the lower portion of the left column on the following page, 194. I'm not sure what's going on with Vc. Is it derived somehow from (81)? The second part of a correction is for the zenith attraction, Vcc, which continues after (81) on page 201. (85) Vcc, and the ΔZ correction is shown in (87). I suppose some of what baffles me about Vc and Vcc is that another source calls Vc the observed speed, and Vcc the vector sum of its and the Earth's heliocentric velocities. Meanings do not match up with the Whipple article. This source provides the same equation as (88).