Originally Posted by slowburner
First national survey 1837 - 1842.
Second national survey 1888 - 1913.
There was a 1" map produced in 1851.
Between 1857 - 79 the 1:500 urban survey was produced.
On a slightly different note. Does anyone know if there is a significant difference between magnetic north in 1842 and today
Isn't the yearly decrease printed on the map?
The actual figures for Mag, True and Grid North are normally printed with reference to a specific date then the annual change is alongside.
afaik (and I could be miles off) there should be a refence North South Grid line which has the deviations written at the top of it or there might be a side box/bottom box with the info referencing where on the map the figures are true for.
...... just been and grabbed the nearest OS map I could find, Discovery Series here and all the info is in a box on the rt hand side of the map. Says 08.6' annual decrease
(as of 1995 for sheet 82) now that might not hold out very well over 150years
But I'm sure that info is at the top somewhere on the old 1:63,000 1inch maps?