Plotting Lakes

Charts of lakes, and islands for that matter but I’ll restrict this analysis to lakes, often differ slightly in their format from those of mountains and rivers. Where the classic comparative is two dimensional, showing rank and size, some (but by no means all) charts of lakes are three dimensional, showing relative latitude and longitude and size.

Are charts of this flavor in violation of a cardinal rule of comparatives, that they must be arranged by size, rather than position on the Earth?

GW Colton's 1865 Comparative Size of Lakes and Islands
GW Colton’s 1865 Comparative Size of Lakes and Islands with characteristic Colton border. Note there is no clear organization by size, but rather lat & long. (Rumsey)

This is a matter of opinion, and there are good arguments that they are truly comparatives: first, I’ve never seen a lakes comparative where the largest lake was not the most prominent, and second, latitude and longitude are ancillary to showing size. But in my mind it’s clear that they do break this rule because rank is not abundantly clear, and that is the criteria by which they are to be compared.

Lakes comparatives have the unique problem of fitting irregularly shaped subjects unto a regular analytical landscape (no pun intended). That’s to say that lakes are not regular geometric figures all oriented in the same direction; their borders meander and their long axes run every which way. If they were regularly shaped, plotting them would be simple. The straight forward approach would be to place an illustration on a page plotted by their width and length on a Cartesian plane. That’s to say that the wider a lake is, the further to the right it is shown and the longer it is the further up it is plotted.

Of course, lakes are not polygons and this system is almost laughable. So what can be done to overcome this? Area is an attractive criteria. Lakes can be arranged on a page, say, starting in the upper left, working across in descending order, then returning to start a new row when the upper right is reached. This would mimic a common sort used for mountains. More complex, one could circumscribe a polygon over the lake, then arrange on a Cartesian plane as described in the ideal scenario above.

What about the criteria used for comparison? Is the largest lake that with the greatest area? That seems the logical choice, and what would easily be assumed by the reader. But other criteria could change the order markedly. What about greatest north to south or east to west span? Or, perhaps ranking the lakes by perimeter? Either of these latter criteria could allow a long skinny lake positioned with its long axis running northeast to southwest and with lots of coves and inlets to pop to the top of the list, ahead of a lake with much greater area. How about arranging by depth? To get down to brass tacks, a scatter arrangement is inappropriate when comparing lakes by either perimeter or depth.

© Peter Roehrich 2015


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