Interpreting What You Can See from the Mat

Above you can view a head of bowls with a long jack as seen from the mat (top) and then taken from just in front of the head (below). Using the rules in the table below you can quickly work out the disposition of the bowls without visiting the head. 

In order to bowl the proper length, you must be able to provide accurate information to your subconscious computer.  You need to tell it whether your last bowl was long or short and by how much. Particularly in singles, this must be done at least part of the time by an estimation done from the mat. You can't go back and forth to the head after every bowl! Even in non-singles games, some skips may not be competent to properly and concisely convey important information. Other skips may modify the truth to save your feelings or as part of their own strategy to correct your play. Such misinformation will only confuse your natural gift for making adjustments.

In lawn bowls, the jack may be placed anywhere from 21 meters to 29.5 meters in advance of the front edge of the mat. My eye level is 66 inches from the ground (I am six feet tall). Thus at 29.5 meters the angle between the horizontal and my line of sight is 3.25 degrees. When the jack is at 21 meters, the corresponding angle for me is 4.56 degrees. My bowls when lying flat have a height of about 4.25 inches and these bowls' diameter is 5 inches, so standing up each has a height of 5 inches.  A jack’s diameter is 2.5 inches. Doing the calculations I get the numbers in the table below.

	Completely see Jack behind Bowl	See half Jack behind Bowl	Completely see Bowl behind Jack	Completely see Bowl behind Bowl
Short Jack	Inches	Inches	Inches	Inches
	49.5	33.9	27.6	53.3
	Feet	Feet	Feet	Feet
	∿ 4	∿3	∿ 2	∿ 4.5
Long Jack	Inches	Inches	Inches	Inches
	71.1	49.1	40.3	74.8
	Feet	Feet	Feet	Feet
	∿ 6	∿4	∿3.5	∿6

It is worth noting that a bowl can be as much as two feet in front of the jack and still completely hide it, so even though the jack is covered a good draw can readily become the shot bowl.  Also, even if the jack is completely hidden as seen from the mat, there can be plenty of room to catch and trail the jack without touching the covering bowl.