A sculptor needs advice please

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07-29-2012 03:17 PM
iestyndavies
New Contributor
I wonder if anyone can help me please ? I have just been commissioned to produce 2 large water features for a prestigious project.
At the centre of each sculpture there will be 2 x 580 mm diameter stainless steel hemispheres welded together. Once welded together to form a sphere the intention is to use a world map in 2mm brass, cut on a CNC machine, which is then to be hand beaten into a
580 mm concave former, then applied and fixed to the stainless steel globe.
My problem is finding the correct map to use, that when cut flat and hand formed gives me the best results in fitting correctly to the globe. I need a world map in 2D that can be exported as a dwg or dxf, for use directly with the CNC software.
I have already been advised that the correct map may be the Equidistant Cylindrical or Plate Carree, although I cannot find this on
the web in sufficient detail or as a downloadable file. I would greatly appreciate any constructive advice
Regards
iestyn davies - www.contemporarychandeliercompany.co.uk
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9 Replies
DavidWilliams
Occasional Contributor
Hi Iestyn,
What you're asking for is straightforward, a couple of questions:
Would you want to show country borders or simply landmasses?
And out of interest, how are you going to handle locating all the islands?
David
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iestyndavies
New Contributor
Hi Iestyn,
What you're asking for is straightforward, a couple of questions:
Would you want to show country borders or simply landmasses?
And out of interest, how are you going to handle locating all the islands?
David


Hi David ,
Thank you for your reply ; I just want to show landmasses. As regards choosing what to leave in and what to ignore, in terms of island detail, we will be just representing the larger Islands. If I were able to get hold of the map in dxf format I would have to edit what
we are and are not going to use , before sending the file to the laser cutters.
All landmasses will be bonded to the stainless globe with an aviation strength 2 part epoxy, then further drilled, tapped and pinned
with small brass grubscrews.
Kind Regards
iestyn
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DavidWilliams
Occasional Contributor
Iestyn,
Take a look at the attached.
You'll find a DXF file of the Americas projected to World Equidistant Cyclindrical.
The whole file takes me over the amount I can send thru the forum, if you send me your email address I'll try sending it from home.
I think the level of detail is sufficient for the size you're working to, let me know what you think.
I could also add a bounding box as a N-S guide for position if that would help.
David
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markdenil
Regular Contributor II
You are missinformed if you are thinking to use either Equidistant Cylindrical or Plate Carree.
These will NOT give you correct shapes on a spherical globe: they project the world on to a cylinder.

What you want is the world WITHOUT any projection: you want what are known as globe gores.
These are the either 'pointed lozenge' shapes (joined along the equator and pointy at the poles) or a flower shape (a round patch at the pole with broadening 'petals' extending to the equator) that get pasted on the globe ball (or tacked on, in your case). The flower type usually has a tape line for the equator, to hide the join.

Although the Plate Carree (or Geographic) is sometimes refered to as 'un-projected', this is a misnomer;
It just means that sperical coordinates are used as cartesian coordinates.

I would suggest using a product like GeoCart (http://www.mapthematics.com/). The people I know who make globes use that to make their patterns.
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iestyndavies
New Contributor
Iestyn,
Take a look at the attached.
You'll find a DXF file of the Americas projected to World Equidistant Cyclindrical.
The whole file takes me over the amount I can send thru the forum, if you send me your email address I'll try sending it from home.
I think the level of detail is sufficient for the size you're working to, let me know what you think.
I could also add a bounding box as a N-S guide for position if that would help.
David


Hi David , Thank you for your time ; detail is over and above what I require. I opened it in Adobe illustrator and then exported
it out into Coreldraw to create the attached PDF - obviously there appears to be a stretch occurring - am assuming this is
unintentional ? Have you got a global version ? e-mail is sales@blowzone.co.uk . Not sure about the relevance of your last comment
to my project. Would this work as a cut out for the project do you think ?
Kind Regards
iestyn
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iestyndavies
New Contributor
Hi David , Thank you for your time ; detail is over and above what I require. I opened it in Adobe illustrator and then exported
it out into Coreldraw to create the attached PDF - obviously there appears to be a stretch occurring - am assuming this is
unintentional ? Have you got a global version ? e-mail is sales@blowzone.co.uk . Not sure about the relevance of your last comment
to my project. Would this work as a cut out for the project do you think ?
Kind Regards
iestyn


sorry ; pdf attached
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DavidWilliams
Occasional Contributor
Hi Iestyn,
Apologies for my delay in replying, work committments...
The "stretch" is intentional, it is the distorting effect of the projection, that's what it looks like.
Having done some quick research on this, I think mdenil is correct and the two projections you mentioned, even when hand shaped, will cause problems.
I found this discussion on the web:
http://gis.stackexchange.com/questions/15639/what-projections-should-i-use-to-make-my-own-globe
Producing gores on UTM looks promising and is pretty easy to setup, I'll have a go over the weekend.
David
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DavidWilliams
Occasional Contributor
Hi Iestyn,
Find attached two sets of AI files.
Each gore (pink area) represents 18 degrees span, you will need to stitch these together in Illustrator - I have included a graticule as a guide.
I'd suggest mocking these up in card before committing to metalwork.
Let me know how you get on.
Regards, Dave
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DavidWilliams
Occasional Contributor
Second set.
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