Wednesday, October 28, 2015

Nerdy Mapping Fun with Faerun and Google Earth, Part I

Updated with a few math fixes

I purchased this awesome and massive detailed map of Northern Faerun by Mike Schley, a digital version of the one included in the Dungeons & Dragons Sword Coast Adventurer's Guide.

The map weighs in at 10200 x 6600 px — a little less if you shave the borders — and also comes with a 34 page even higher detail PDF version. If I get ambitious I might stitch that together and use that instead.

However, at this scale the map really needs to be on a globe, for which Google Earth will do nicely. Now, some literature suggests Toril is slightly larger than Earth, some literature says the same size, but as far as I know Google Earth doesn't allow for rolling out your own planets, so our Earth will have to do.

First off, it is easy enough to overlay an image in Google Earth. In the menu bar: Add | Image Overlay. Wait a bit for the image to load. Then, change to the Location tab in the New Image Overlay popup and click the "Convert to LatLonQuad" button. This will give you the ability to set the four corners independently.

The Edit Image Overlay dialog's Location tab then lists four corners with Longitude and Latitude. The 1st corner is Southwest (bottom left) then Southeast (bottom right), Northeast (top right) then Northwest (top left).

The map legend is about 1820px = 500 miles. After shaving the borders I ended up with a map that was about 2674 x 1696 miles. Further, I assumed that this is actually a Mercator projection and so the distances are accurate North-South, but that East-West the scale is only accurate at the middle of the map.

Given those assumptions, everything is nicely parallel, with the Southern edge of the map ending up at about 3,124 nautical miles while the Northern edge is only 2,074 nautical miles.

I picked a starting point where Baldur's Gate will end up roughly on top of Los Angeles, CA (Waterdeep at Ashland, OR and Neverwinter at Seattle, WA). Using formulas from Allen Wyatt's ExcelTips I started plugging numbers into Excel.

I converted each LAT/LNG pair into radians using this formula:

=RADIANS((DEGREES*3600+MINUTES*60+SECONDS)/3600)

Then plugged a N-S pair into Excel, and adjusted, to get one edge using this forumula:

=ACOS(SIN(LAT1)*SIN(LAT2)+COS(LAT1)*COS(LAT2)*COS(LON2-LON1))*3443.89849

With that done, I took the mid-point between the North South edges, and plugged those into the same formulas to get the East West coordinates. I plugged those numbers back into the Google Earth location tab on the image overlay. And success!

Hard to see here but if you look close you can see the latitude and longitude markings.

The final values I used were:

  1. 1st Corner: 150° 0'0.00"W Longitude and 24° 0'0.00"N Latitude
  2. 2nd Corner: 92°12'0.00"W Longitude and 24° 0'0.00"N Latitude
  3. 3rd Corner: 92°12'0.00"W Longitude and 52°16'0.00"N Latitude
  4. 4th Corner: 150° 0'0.00"W Longitude and 52°16'0.00"N Latitude
Nerdy Mapping Fun
  1. In Part I I overlay a map of Faerun on Google Earth.
  2. In Part II, Stitching it Together I repeat this process with the 34 part PDF map.
  3. Part III, Higher Resolution and now moving it around.
  4. In Part IV, KML Files I use KML files to display maps at different zoom levels.

6 comments:

  1. Nice. To match climates a bit better, I might push Neverwinter up to Vancouver, BC, but other than that, this is brilliant, I may have to play around with it myself

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  2. I tried various starting latitudes including pushing the whole thing further North. However, the jungle of Chult, in other maps, lie what looks to be about 6 degrees South of the southern map edge. I wanted to keep that in the tropics, so I pushed it North as far as I could with that self-impoaed restriction.

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    1. it seems a bit further south than that to me, see: http://www.nj-pbem.com/data/Maps/Overview.htm

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  3. I was working off this map https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcS5GYmPHFfTG9IzTd_NiAdfjsPHUHywNc5OwpwG_xeyKcjJHtH6, You are right however, the map you linked has closer to a 10 degree separation. In either case, if you want the Chult to be just at the edge of the Tropics, you could push the edge at least 4 degrees N, maybe more. I'll do another version and update it.

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  4. And here it is pushed 4 degrees North. http://www.autogenerated.com/2015/10/nerdy-mapping-fun-with-faerun-and_29.html

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    Replies
    1. Love it, thanks for all your ingenuity!

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