IS-WAS Distance to Track

kverdon · 01-05-08, 01:40 PM

Hi all, I've been reading the topics on the IS-WAS and have read the 1922 IS-WAS manual. I think I've got it down on how to calculate the course to a 90 degree track but I can't get the picture on how to calculate the distance to track. Here is how it is explained in the Manual:

On the transparent enemy card is engraved a semicircle marked off into equal squares. On the rear end of the periscope pointer, along its centerline, are a series of transverse marks spaced apart a distance equal to the side of a square, (Note: On Submarine Attack Course Finders Mark I Mod. 3 Nos. 301 to 306, these marks occur on both ends of the pointer). Any convenient number of hundreds or thousands of yards may be assigned to each division so that the initial range can be indicated on the periscope pointer by stepping out from the center of the device the requisite number of divisions. Should the point thus arrived at lie outside of the semi-circle, a larger number of yards must be assigned to each division so that the point will come within the semi-circle. By noting the position of the point; (a) with regard to the centerline passing through the enemy vessel there is obtained graphically an estimate of the shortest distance to the track of the enemy vessel, (b) with regard to the line passing through the center of the enemy vessel at 90° to its course there is obtained graphically an estimate of the distance the enemy ship must run to bring abeam own vessel's initial position.

I can follow it down to "By noting the position of the point; (a)"...... Which point are they refering to? and which centerline? Is there someone out there who has played with the IS-WAS that can translate this a bit better for me.

MUCH THANKS!

Kevin

01-05-08, 01:40 PM	#1
kverdon Seaman Join Date: Jan 2002 Posts: 36 Downloads: 13 Uploads: 0	IS-WAS Distance to Track Hi all, I've been reading the topics on the IS-WAS and have read the 1922 IS-WAS manual. I think I've got it down on how to calculate the course to a 90 degree track but I can't get the picture on how to calculate the distance to track. Here is how it is explained in the Manual: On the transparent enemy card is engraved a semicircle marked off into equal squares. On the rear end of the periscope pointer, along its centerline, are a series of transverse marks spaced apart a distance equal to the side of a square, (Note: On Submarine Attack Course Finders Mark I Mod. 3 Nos. 301 to 306, these marks occur on both ends of the pointer). Any convenient number of hundreds or thousands of yards may be assigned to each division so that the initial range can be indicated on the periscope pointer by stepping out from the center of the device the requisite number of divisions. Should the point thus arrived at lie outside of the semi-circle, a larger number of yards must be assigned to each division so that the point will come within the semi-circle. By noting the position of the point; (a) with regard to the centerline passing through the enemy vessel there is obtained graphically an estimate of the shortest distance to the track of the enemy vessel, (b) with regard to the line passing through the center of the enemy vessel at 90° to its course there is obtained graphically an estimate of the distance the enemy ship must run to bring abeam own vessel's initial position. I can follow it down to "By noting the position of the point; (a)"...... Which point are they refering to? and which centerline? Is there someone out there who has played with the IS-WAS that can translate this a bit better for me. MUCH THANKS! Kevin