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jumpjack
02-05-2009, 08:44 AM
I found these instruction on internet about which projections are needed to build a 3d earth globe:
"Create a series of 12 Transverse Mercator projections that are 32 degrees in longitude and 91 degrees in latitude to form a "flower petal" projection for making globes. If the northern hemisphere is being created, the latitude range is -1 to +90. If the southern hemisphere is being created, the latitude range is -90 to 1. The petals are formed by changing the center longitude and map rotation in steps of 30 degrees for each Transverse Mercator projection. Each section is put into the mosaic. The final center of the projection is a Lambert Azimuthal Equal-area centered on the pole and covers from -90 to -75 or 75 to 90 degrees latitude and 360 degrees in longitude. This is the last cube that is placed in the mosaic"

But I can't find suitable (free) programs to obtain needed projections!
Any help?

I need a Java or Windows program which any raster image input and produces raster output.

Steel General
02-05-2009, 08:54 AM
Does Google Earth do that kind of stuff?

bartmoss
02-05-2009, 08:57 AM
Nope google earth doesn't do anything like that.

Your easiest choice is to use a flattened dodecahedron (20-sided die) map, sort of like the maps traveller used, and then glue the sides together appropriately.

Either that, or just paint your map on a spherical object to begin with.

jumpjack
02-05-2009, 09:07 AM
Does Google Earth do that kind of stuff?

it just SHOWS a globe, I need to PRINT it to BUILD it. ;)

jumpjack
02-05-2009, 09:09 AM
Nope google earth doesn't do anything like that.

Your easiest choice is to use a flattened dodecahedron (20-sided die) map, sort of like the maps traveller used, and then glue the sides together appropriately.

Either that, or just paint your map on a spherical object to begin with.

no, I want to print one of these:
http://astrogeology.usgs.gov/Gallery/MapsAndGlobes/

But I want to be able to choose MY map and MY size.

Steel General
02-05-2009, 10:20 AM
it just SHOWS a globe, I need to PRINT it to BUILD it. ;)


Sorry I misread what you wanted to do :?

waldronate
02-05-2009, 01:31 PM
You can do a globe with many different kinds of projections. The idea is to get small enough pieces to cover the globe without too much distortion when you paste them down. For example, sinusoidal gores (optionally with azimuthal equidistant endcaps) work well.

I have used Fractal Terrains ( http://www.profantasy.com/products/ft.asp and Wilbur ( http://www.ridgenet.net/~jslayton/software.html ) to generate images for such projects in the past, but there are more modern programs out there such as G.Projector ( http://www.giss.nasa.gov/tools/gprojector/ ) or FlexProjector ( http://www.flexprojector.com/ ) that might be better suited for the task. G.Projector wants input in the equirectagular projection but that's doable (I have successfully used my elderly ReprojectImage program at http://www.ridgenet.net/~jslayton/ReprojectImage.zip for this task). I haven't done much more than just barely play with FlexProjector so I can't say how useful it would be in this context.

There were a few discussions here about making globes here a while back ( http://www.cartographersguild.com/showthread.php?t=2109 is one) so there is probably additional information drifting around.

Attached is an example of the old Forgotten Realms Interactive Atlas map reworked for cutout and paste to a globe. It was reprojected from its original Equirectangular projection to the one shown in one step in Fractal Terrains.

RobA
02-05-2009, 04:04 PM
I also responded in this thread:
http://www.cartographersguild.com/showthread.php?t=4216

Not sure if they are for the same thing or not. If OK, I would like to merge the threads.

-Rob A>

jumpjack
02-06-2009, 03:54 AM
Y
I have successfully used my elderly ReprojectImage program at http://www.ridgenet.net/~jslayton/ReprojectImage.zip for this task).


I played a bit with it, but I can't figure out how to produce a Lambert Azimutal Equal Area projection centered on north pole, can you please help?



There were a few discussions here about making globes here a while back ( http://www.cartographersguild.com/showthread.php?t=2109 is one) so there is probably additional information drifting around.

Thanks, I searched the forum a bit, but didn't find that thread.


@Roba:
yes, it's the same subject, I posted in different forums because I didn't know which one was the more suitable (i.e. which section usually is read by users knowing solution to my problem :) )

waldronate
02-06-2009, 04:24 AM
ReprojectImage takes an image in some projection other than Equirectangular and produces an image in the Equirectangular projection. This step is usually the hard one. You would then take that image and run it through a piece of software such as Wilbur or Fractal Terrains (I'm most familiar with those two as I wrote them).
In Wilbur you would reproject the Equirectangular image as follows:
1. Load the image using File>>Open with the Type set to Color Image Texture.
2. Set the map boundaries using Surface>>Map Info (Top=90, Left=-180, Right=180 and bottom=-90 for a whole-world image).
3. Reproject the map using Window>>Map Projection. Pick the desired projection (Lambert Azimuthal Equal-area in this case) from the drop list and drag the image in the window around to get the desired result. For world endcaps you will want a Center of Projection with Latitude=90 for the north pole and Latitude=-90 for the south pole.
4. Click Export BMP on the Map Projection window to save a bitmap of the desired resolution.

Below are examples of this process on a basic Earth map to get polar caps.

jumpjack
02-06-2009, 05:49 AM
R
Below are examples of this process on a basic Earth map to get polar caps.
Cool, looks like it's exactly what I need! :)
But I can't install Wilbur on my office PC, as the installer requires administrator privileges?!? :?:
Isn't any ZIP/portable version available?

edit:
...and I can't download Fractal Terrains as it appears as a "Game" site! :-(

waldronate
02-10-2009, 12:52 AM
Try installing directly from the msi file rather than the exe in the WIlbur setup - it might work better.

jumpjack
02-10-2009, 03:28 AM
Try installing directly from the msi file rather than the exe in the WIlbur setup - it might work better.
I found two better solutions:
- I waited till I went home and I installed Wilbur on my home PC :)
- I installed a virtual PC on office PC ;)

But now I have another difficulty: how do I know how large the saved image must be (proposed size is always 1024x1024) to "match" the sinusoidal projection which I used to obtain the petals?
Let's suppose the starting image is 640x320 size.

waldronate
02-10-2009, 04:23 AM
Pick any size that you want. It's the inches / degree at constant dpi when printing that's important, not the image size.

For an arbitrary ball, the length of a pole-to-equator sinusoidal gore will be (ball diameter * pi / 4). A common 10-inch playball give a 7.85 inch gore (10 * 3.1415927 / 4).

With a 10-inch ball, you need a sinusoidal gore that's 7.85 inches long pole to equator. If you are using an image that's 320 pixels high, then the pole-to-equator distance is half of that or 160 pixels. 160 pixels / 7.85 inches = 20.4 pixels/inch (very low resolution). To get an endcap that's 15 degrees radius and printed at the same ppi then you'll need an image that's 2/6 of the 160 pixels (15 degrees / 90 degrees = 1/6 radius * 2 = diameter) or 53.33 pixels) or 53 pixels.

For a more reasonable 2048 height image then you're looking at 130 ppi and 341 pixel endcaps.

jumpjack
02-10-2009, 09:10 AM
Pick any size that you want. It's the inches / degree at constant dpi when printing that's important, not the image size.

For an arbitrary ball, the length of a pole-to-equator sinusoidal gore will be (ball diameter * pi / 4)[...].
Thanks, I think now I got the point.
Given ball diameter D, I need a W x H map, where:
W=2*H
H=D*pi/2 (H/2 = C/4 = 2*pi*r/4 = D*pi/4)

Given this map, I need, for a Lambert projection 30 wide, an image WL wide, where:
WL=D*pi/12 (WL=C*30/360 = C/12 = 2*pi*r/12 = D*pi/12)

I hope it's correct.

RobA
02-10-2009, 10:13 AM
Here is an inspirational video for you:

http://videos.howstuffworks.com/science-channel/5058-how-its-made-globe-video.htm

-Rob A>

jumpjack
02-10-2009, 01:34 PM
Here is an inspirational video for you:

http://videos.howstuffworks.com/science-channel/5058-how-its-made-globe-video.htm

-Rob A>

thanks, very useful.
I need a rod. :)