[Proj] Lat-Lon values under different ellipsoides

[Duncan Agnew]

Jan:

         I would say that it is better not to have a different ellipsoid
change the ellipsoidal coordinates (which is what lat/long are).

         It may also be that you are looking at the difference betweeen
astronomical latitude and geodetic. The latter is what you get if the
reference for the local vertical is the normal to the ellipsoid; the
former, easier to do, assumes the local vertical is the direction of the
plumb line. The difference is the deflection of the vertical, which 
depends
on the slope of the geoid: I don't know what this is for the 
Netherlands.
It is quite possible that the 1850 values are astronomical: you'd need 
an
expert on local geodetic history to find out

Duncan Agnew