A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2016 Mar 1, 14:23 -0800
I wrote previously:
" In latitudes outside the tropics, this implies a different plotting scale for roughly every degree of latitude (eventually approaching every 34' of latitude at very high latitudes). From roughly 10° to 22°, it's approximately every two degrees of latitude."
Just for completeness, if you want to stay within 1% on the scaling factor, the acceptable latitude range in minutes of arc is 34/sin(Lat). Suppose you have a scaled plotting sheet for 12° latitude. For that latitude, the quantity 34/sin(Lat) is +/-163' or 2.7° so you can safely use that scaled plotting sheet anywhere from latitude 9.3° to 14.7°. Another case: if you have a scaled plotting sheet for 45° latitude, the acceptable latitude range is +/-48'. You can use the plotting sheet within 0.6° of the central latitude, but you really should use a different plotting sheet for 44 or 46°.