The trig and mapping situation is complex. Here I am straddling the Franco-Belgian frontier and several different sets of trig data (of varying antiquity) exist for the region.
The trigonometric problem is that although others have begun to use the Belgian spheroid, origin, azimuth, and sheetlines as the basis for their own survey (referring the French data to these), the absence of central geodetic control at some GHQ leaves each of us to our own devices.
My situation is difficult: I have to reconcile the trig and leveling data of the various systems available for this area (including the French admiralty triangulation and British cross-Channel work) with my own emotions—complex mathematical calculations and a feeling of loss.