So what are you pulling out from Bowditch? Meridional Parts, one of which is equal to one minute of longitude at the equator. Because Meridonal Projection Charts are stretched vertically in order to maintain the correct shape and direction ratios between objects on the chart, meridional parts are used to determine the amount of stretch on each chart. For example, at 50°N, there are 60 meridional parts in 1° of longitude, and about 94.1 meridional parts in 1° of latitude. So, a chart from 47-52°N would be 1.4 times as tall as it is wide.

 -If you know the size of your paper, first find the appropriate scale to use for your chart in the following steps.

 

Step 2: Multiply the number of degrees to be found along the horizontal axis by 60 to find the number of meridional parts along that axis.

 

Step 3: Next, go into Bowditch, Table 6, and find the number of meridional parts between the desired latitudes.

 -Subtract the number of meridional parts of the lower latitude from the higher latitude to find the number of meridional parts along the vertical axis of the desired chart

 

Step 4: Divide the dimensions of your chart by the number of meridional parts on the vertical axis and the number of meridional parts on the horizontal axis to find the inches per meridional part(MP).

 

Step 5: Figure out your limiting dimension, or which axis will limit the size of your chart. Do this by comparing the ratio of inches per MP; whichever is the smaller number will be the limiting dimension.

 -If along the vertical axis there are 0.5 inches per MP, and along the horizontal axis there are 0.3 inches per MP, you must use 0.3 inches per MP along both axes so that everything will fit onto the chart in the dimensions provided.

 -For example if there are to be 100 MP along the horizontal and 100 MP along the vertical axis, but the paper you have is 10 inches wide by 6 inches tall, you couldn't fit the entire vertical range in using the horizontal's ratio; it wouldn't all fit.

 -By using the smaller scale, you will have excess space along the axis with the larger ratio. Simply continue on labeling this scale until you reach your borders.

 

Step 6: Draw your chart using the appropriate ratio.

 -First draw your borders, then find your center lines so that you have some point to reference for your measurements.

 -Draw the meridians first as they will be equally spaced.

 -Look back through Bowditch to find the number of MPs between each degree of latitude on your chart. On a large scale chart, the number of MPs wont vary much from top to bottom, but on a smaller scale chart, there will be many more MPs at the top of the chart than the bottom (the spacing will change)

 

Step 7: Draw a minutes scale to make you measurements easier.

 -If you know the number of MPs per degree, you can divide by 60 to find the number of MPs per minute, and can draw these along your axes to make plotting that much easier

 

Step 8: Crack a beer and head up to watch man, you're done.

 -If this was confusing please let us know at deckskills@gmail.com, it happens, let us know how to fix it if you can. Thanks