Geodesics

Tips and tricks for using Geocart 3
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Maezar
Posts: 12
Joined: Wed Jan 21, 2015 10:43 pm

Geodesics

Post by Maezar » Sat Oct 13, 2018 5:58 am

Hi there,

It's been some time so I thought I'd request again to have some simple geometric solid projections.

I would love to be able to project a map onto a Regular Dodecahedron or Icosahedron.
If this isn't possible natively, are there some "long hand" steps that could achieve a passable result?

Thanks and best regards,

M

daan
Site Admin
Posts: 721
Joined: Sun Mar 29, 2009 12:17 am
Location: Seattle

Re: Geodesics

Post by daan » Sun Oct 14, 2018 11:19 am

Maezar wrote:Hi there,

It's been some time so I thought I'd request again to have some simple geometric solid projections.

I would love to be able to project a map onto a Regular Dodecahedron or Icosahedron.
If this isn't possible natively, are there some "long hand" steps that could achieve a passable result?

Thanks and best regards,

M
Hello Maezer.

There are two generic ways I know of to produce a useful projection for a polyhedral face: conformal or gnomonic. Geocart does not offer a generic conformal regular polygon, so that would be out. That leaves gnomonic. With a gnomonic projection centered on each face, the graticules of each face will match up along the edges, although, unlike conformal, they will be kinked where they meet up.

The long-hand steps would be:
1. Identify the geographical center point of each polygon face.
2. Create a gnomonic map for each face, centered on the geographic center of that face.
3. Crop each map to the shape of the face’s polygon.
4. Assemble.

Does that help?
— daan

Maezar
Posts: 12
Joined: Wed Jan 21, 2015 10:43 pm

Re: Geodesics

Post by Maezar » Wed Jan 16, 2019 4:10 pm

Yes, that helps. Thank you! (It's been awhile, but I'm back on this :-))
I will struggle a bit with how to do the face centering. Any tips would be helpful, especially for the dodecahedron.

daan
Site Admin
Posts: 721
Joined: Sun Mar 29, 2009 12:17 am
Location: Seattle

Re: Geodesics

Post by daan » Wed Jan 16, 2019 5:10 pm

As it happens, I’m working on this at this very moment. :-)

Best,
— daan

Maezar
Posts: 12
Joined: Wed Jan 21, 2015 10:43 pm

Re: Geodesics

Post by Maezar » Wed Feb 20, 2019 8:39 am

> I’m working on this at this very moment.

This is really great news!

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