variation vs grivation

[wingman1]

could someone please explain the difference between normal variation and grid variation?

in the REF example in cfs it shows two at one aerodrome location, 25 degrees east, then, gv10 degrees west.

[Tango01]

Read this:

http://www.ordnancesurvey.co.uk/oswebsi ... north.html

[Trapper]

Tango 01 hasn't quite addressed Grivation as it applies to operations in the polar regions of Canada / Alaska. Depending on how urgently you need this information I can download a copy of the way the Military does it in Canada. But first I will have to scan the paper copy first.

It's about 10 pages long if I remember correctly, and I should be able to do it tomorrow.

I will include it as a link in my next message in case others want to download it too.

Trapper

[ahramin]

Thanks Trapper, looking forward to it.

[wingman1]

sure, if you don't mind going through all that trouble, it would be much appreciated.

thanks

[ahramin]

Here is Trapper's paper.

[reunionnais97432]

The main reason grid navigation used, is that at high latitudes, the amount of meridian CONVERGENCE becomes significant.
The difference between True direction and Grid direction is known as CONVERGENCE.
For Grid steering, all we have to do is apply Deviation to convert compass heading to Magnetic heading then, apply the difference between Magnetic direction and Grid direction. e call this GRIVATION and it is algebraic sum of Variation and Convergence .

GRIVATION = Variation+Convergence.

If a magnetic diection is required from a Grid direction the convergence and variation must be applied.

GRID CONV TRUE VAR = MAG
090 10E 080 10E 070


If the Greenwich meridian is the chosen datum. the grid is known as a "Standard grid" (mainly used in europe).
Someone can confirm that a favorite datum often used in Canada is 060°W ?