Oahu Shaded Relief
Oahu Shaded Relief
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Well, I finally got around to making one of those Blender shaded relief renderings, and I chose to extrude the relief on top of a historical map of Oahu from 1881 (check out davidrumsey.com for a really incredible archive of historical maps like this one). While making maps like these is a popular activity among #GIS amateurs and professionals alike, and it's obviously very cool that one can render more realistic lighting than a simple hillshade, it's the inconsistencies discovered in the process of making the map that I found more interesting.
Having been created in 1881, this map was made during the last years of Hawaii's existence as an independent nation. In 1893, a small group of sugar and pineapple-growing businessmen, aided by the U.S. minister to Hawaii and backed by heavily armed U.S. soldiers and marines, overthrew the Queen and instituted a military-industrial dictatorship (now known as the Dole Food Company). After being annexed into the United States in 1898 - part of McKinley's expansionism in the Pacific, which also included Guam, American Samoa, and the Philippines - Hawaii remained a territory for 60 years, a convenient status for agricultural capitalists seeking to import cheap, foreign labor, or for a U.S. military looking to project naval power into the Pacific.
So what did I see when I was creating this map? I saw that the coastline shapefile I used to clip the DEM didn't match the historical coastline in Keehi or Kaneohe; the reef and ocean floor in these locations has been dredged to create runways for Honolulu International Airport and Marine Corps Base Hawaii, respectively. I saw that the modern-day hydrology of the island's central valley didn't line up; the Dole plantation in Wahiawā dammed the Kaukonahua Stream in 1903 to irrigate their fruit crop, drastically reducing the amount flowing into to Oahu's underground aquifers (Oahu has been subject to repeated water crises in recent years). And when I went searching for more documentation on this map, I found a copy of it in the Library of Congress with a big red line scrawled around it. This line, added years after the fact, demarcated the Oahu Railway, an 1890s project by agricultural capitalists to service their growing sugarcane plantations.
All of this serves as a reminder that in cartography, there is always more than meets the eye. Maps are a reflection of the time they're made, and just because a map is made for one purpose doesn't mean it won't be used for another. Most of all, maps are just another way to represent data, which is to say they can show or hide as much as the creator wants; like charts and graphs, maps can mislead, omit, or even downright lie. So even when met with a seemingly innocuous project, it's the cartographer's responsibility to understand and communicate the context, intention, and story behind what others may pass off as a simple hillshade.
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