How to make the continents on a big metal globe in 10 easy steps
Or maybe not so easy. I had such a hard time figuring this stuff out that I thought somebody else might benefit from my experience. I don't want to drive down business, but a few more big funky metal globes in the world wouldn't be a bad thing. And if you have the wherewithal to do it yourself you probably wouldn't be hiring me anyway.
The following is a rough and incomplete outline of one method of doing this. There are other methods. Easier methods. There are also probably open-source (and free) replacements for Photoshop. I just haven't found one that actually works for this. Gimp
can output the PPMs and convert back to PNG (probably quicker than ImageMagick) but it doesn't create paths and it doesn't open RAW files without a plugin. I couldn't figure out how to make the plugin work, so I gave up. If anybody can really do this (as opposed to saying they know that it should work), just let me know
. I'll try to keep this page updated with anything useful, and you can always add your own notes to the comments
This "tutorial" (if you can call it that) assumes that you know your way around the block. I'm too lazy to make this into "The Idiot's Guide for Globe
Construction". However, it should help point you in the right direction or at least give you a few ideas.
Minimum Tool Requirements
Go to the Globe project at NOAA, and get the tiles.
Yes, they are big, but they are free (unless you buy the CDs for $260). One of them is nearly 60 MB, but most are 20 to 30. Better make sure you have either broadband or a whole lot of coffee.
Import to PhotoShop and combine the whole thing into one big image.
Lose the irrelevant channels and save the image as a two-color PNG.
Your file will now look sorta like this:
PPM is a very inefficient format, because the file is written as a rectangular grid. A 1.1 MB PNG can become a 667 MB PPM, so make the PNG as few pixels as you can get away with, or the next steps will be really slow.
Convert to PPM with ImageMagick like this:
convert in.png out.ppm
And then go have some coffee. Across town. Walk there.
Split the PPM into gores with Perl and make_gores.pl
Usage: $0 in.ppm out.ppm number-of-gores
perl make_gores.pl in.ppm out.ppm 12
Convert back to PNG like this:
convert in.ppm out.png
Your file will now look sorta like this:
In Photoshop, create a path by selecting some white, select similar, new path from selection, save path, export path to illustrator, yadda yadda. You may have to screw around with various settings to make it work.
Open the path in your CAD program and clean it up. I managed to get the path open with Rhino , but only after saving it with DOS line endings in BBEdit (it doesn't suck™). Otherwise, Rhino wouldn't open it and just crashed.
You will want to be careful to get rid of the tiny islands, or you will have a lot of little dots that you couldn't use even if you could figure out where the heck they go.
You can reduce the detail, but don't get too carried away. Look at Japan and England. They should be more or less recognizable.
Some things may want a little redo. Greenland can generally be one piece, but it gets cut up because it's so close to the North Pole. Either patch it back together in CAD, or go find a map online. It's not hard. And Antarctica. You really don't want 12 or 24 pieces. Find a map and scale it. And then cut maybe 4 darts in it so you can make it spherical.
Export to your favorite CAM format and cut it out. I saved the file as a DXF and converted it for my cutter with SheetCam, which is a fantastic cheap 2-1/2D CAM application with G-Code and HPGL output.
Hammer your pieces into shape and weld to the globe's frame.
Which might look sorta like this:
This 8 foot CorTen steel globe (to eventually be part of a sculpture in front of my building when I have time) was made with 24 gores. It should have really been more, or perhaps segmented somehow, so that there were more segments near the equator. Oh well. Next time maybe. And maybe thicker material (this was 11 ga.) would have helped. The North America on the wall above the globe was 1/4" stainless (same scale) that I did as a test. It came out remarkably smooth, although it's higher up from the equator, so the width of the pieces was less.
There is no step 10. Unless you want to go back to the coffee shop. You don't have to walk this time. You can ride your bike.
The first globe with continents that I was hired to make was a challenge and a bit of a nightmare. It was a large globe (16 feet across and 10 feet tall, to make a little room in a theme restaurant bar), so I thought I could just beat some aluminum into shape and piece it together. After an hour of hammering, I was so frustrated that I was ready to cry. I'd made a huge amount of noise and an unsightly lump in a 4' x 10' sheet, but there was no way it was going to be usable. I didn't have a clue what to try next.
I ending up making 1/12th vertical gores about 4 feet wide with horizontal darts in the edges about every 16 inches. Then, after hammering and welding them into shape, I eyeballed the continents from a 12" globe and cut everything out. It was a ludicrous amount of work, and the result wasn't as smooth as it should have been. Here
A couple of years later, I got asked to do the same exact thing again. In the interim, I'd built a CNC
plasma cutter, so I imagined I could cut it out easier. Since I couldn't figure out where to find good geographic information, I used the same 12" globe, traced the continents on vellum, and scanned it into the computer. I then had to manually draw all the shorelines, which was another fantastically labor-intensive task. And thus, my lifelong hatred of CorelDraw.
Finding a way to import the basic geographic data without a lot of hand work has been the global holy grail for me. The process isn't perfect yet, but it's a whole hell of a lot better than my first pass.
* Can't I just open the path in Illustrator and save it as a DXF?
For whatever idiotic reason, Adobe Illustrator has seen fit to export its DXF files with only Macintosh style (\r) line-endings. This is completely insane, because 99% of CAD programs that people actually use run on Windoze, and most of them will only read Windoze (\r\n) or Unix (\n) style line endings. So if you want to open the friggin file, you have to run it through a line-ending converter. Yes, they're easy and available everywhere, but it's not something that the ordinary guy is going to know about. And it's completely avoidable. For Chrissakes, a DXF file is supposed to be "a CAD data file format, developed by Autodesk as their solution for enabling data interoperability between AutoCAD and other programs." Since AutoCAD won't even run on a Mac, what the hell is the point of a DXF with Mac line endings? I don't know what they're smoking, but I want some of it.
To make matters worse, every curve is written as a spline
, which often causes problems with CAD/CAM systems. And the only way to fix this in Illustrator involves turning the whole thing into about a zillion tiny little straight lines. Which will frequently cause other CAD/CAM issues. Sheesh.
However, Illustrator does have some nice features. It can simplify curves and reduce points, which is helpful. If you have it and can deal with the problems, it might be helpful after all.
(This applies to the Mac version of Illustrator CS. I have no idea what the latest version does.)
And finally, if there was a decent CAD program that would just import SVG
files, all of this bitching would likely be irrelevant.
Posted by Hal Eckhart at February 26, 2006 10:00 PM