[NLRS] 10 mile rule (WAS: dupe sheet specs)

[Baker, Donn B]

Duh!
A simple-minded arithmetic error in the diagonal numbers below... I did SQRT(x*y) and NOT SQRT(x^2+y^2).  Dumb!

The correct numbers are:
Sub-Sq size 
at:						Max diagonal
54° = 	2.88 mi x 2.94 mi		4.12 mi
45° = 	2.88 mi x 4.07 mi		4.99 mi
24°30' = 	2.88 mi x 4.55 mi  	5.38 mi

73 Donn
WA2VOI/0

-----Original Message-----
Sent: Thursday, September 21, 2006 6:11 PM
Subject: [NLRS] 10 mile rule (WAS: dupe sheet specs)

A sub-square is 2.5 minutes of arc of latitude(N-S) by 5 min of arc of longitude (E-W).  

One (1) min of arc of latitude = 1 nautical mile (by definition), and for practical purposes is constant from pole to pole. (Yes, the earth is not a sphere, but its close enough.)

The physical length of 1 min of longitude varies from '0' at either pole, to 1 nautical mile at the Equator.  Therefore, the length of 1 min of arc of longitude at any latitude is 1*cos(lat).

Here in MPLS (45°N), this works out to 0.707, so the EN35ja sub-square (for
example) is 2.5 NMiles N-S and 5*0.707=~3.54 NMiles EW.  (Ok, OK. A NMile is 6076.8' or 1.15 Statute miles, so EN35ja is ~2.88 x 4.07 miles.)

So what does this mean re: Doug's comments ?
The southern most part of the US (Key West, FL) is about 24° 30' N (and about the same as Baja CA.)  The northern most part of the US (Angle Inlet,
MN) is 49° 30' (give or take). But, Canada is more northerly than that, so lets go north of Edmonton, AB, or 54°

Sub-Sq size 
at:						Max diagonal
54° = 	2.88 mi x 2.94 mi		2.91 mi
45° = 	2.88 mi x 4.07 mi		3.42 mi
24°30' = 	2.88 mi x 4.55 mi  	3.62 mi

The MAXIMUM difference, then, is 4.55-2.94 or 1.61 miles, E-W. This is ~16% of the minimum valid move between operating locations between the MAXIMUM northern and southern positions.  

Note that it's very, VERY difficult to make a valid move with-in ANY sub-square.  I'd say impossible, even given road miles vs. air miles.

73 Donn
WA2VOI/0

At 10:26 21-09-06 -0500, Doug Reed wrote:
>
>
>Last weekend we discussed the 10 mile rule a couple times during meals. 
>Every time I suggested that sub-grids be used as part of the 
>determination, I was told they don't matter but here we are using them 
>to check for dupes.<g>
>
>I'd still like to have the rule changed to something like "every new 
>operating location must be a minimum 10 road mile move from the last 
>operating location and every QSO must be from a different 6-digit 
>sub-grid." This does penalize the southern states where sub-grids are 
>larger, but I'm not sure how much the actual difference is.
>
>73, Doug Reed, N0NAS.


_______________________________________________
NLRS mailing list
NLRS at mailman.qth.net
http://mailman.qth.net/mailman/listinfo/nlrs