Beginning my quest to map a local nature reserve with pre-1500s mapping tools (learn more here), the first hurdle is figuring out exactly what I need. The first step is to figure out how areas were mapped in the 15th century.
Really, you just pick a starting point, measure the angle and distance to another point, and another, then graph all the points on a chart and you’re done!
Making an accurate map, and figuring out where to place it on the globe, on the other hand, requires a few tools:
Finding heights – Since I’ll be doing a bird’s-eye view map (“satellite” map), I won’t really need to measure heights of the land, but if I wanted to pin down where exactly on the globe my mapped area belongs, I’ll need to know the angle of the sun. And that’s pretty high up in the sky! By this era, I would be able to use an Astrolabe or Quadrant. By the end of the 1400’s Mariner’s Astrolabes were in wide use.
Finding exact location – Using the angle of the sun, I can figure out how far North or South my reserve is (latitude), but then we need a very accurate clock for telling how far East or West it is (longitude). If I’m on land (which this nature reserve is!) I would have been able to tell what time is fairly well by the end of this century with an early clock. But not at sea! And sundials were only so accurate. So we can safely say that I’ll need a sundial, and the location of my area on the planet will be a bit of a guess.
Finding direction – Thankfully, the compass appeared out of the mist, potentially from China, and was well used by the 15th century, so I will have no problem figuring out which direction something is pointing, and horizontal angles!
Measuring distances – On land, I get to use measured rope or chains. If I need to, I can also calculate how long my normal walking steps are, and measure that way, if I need to look a little less suspicious than walking through the woods with a rope…
Here’s the thing though:
If all of these tools were available by the middle of the 1400s, then why did maps still end up like this?
Awesome, but highly inaccurate! Some of the issues come from not being able to find accurate latitude and longitude coordinates. Understandable. Another good reason is that maps were made from multiple different sailor’s logs, so the cartographer was essentially stitching together stories, some creditable, some not. Also, understandable.
The final reason is that surveyors simply didn’t use all of the tools available to them! Various reasons for that, but no one was seriously mapping the world just yet. That was going to change soon after, but that’s a history lesson for another day. Now that I have a list of tools I’ll need, the next step in the adventure is to go on a quest to acquire my gear!