Mercator Projection

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Permalink Reply by Danny Boyes on February 12, 2011 at 5:21pm

Hi Chris,

The question is how accurate do you need to be? Lat long to UTM conversion is reasonably accurate but going UTM to Lat long gets worse results.

I've done quite a bit of work getting results from this recently and if you get nothing more helpful by Monday morning, when I'm back at work, I'll send you something.

Danny

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Permalink Reply by Chris Wilkins on February 12, 2011 at 6:22pm

Send it over!!!

 

Any reasonable approach will work for the moment. If more accuracy is needed then it can be pursued later.

 

Thanks!!!

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Permalink Reply by Chris Wilkins on February 14, 2011 at 6:06am

Here is generating of Earth KML Placemark elements based on Rhino geometry:

(I'm bumping my own discussion with this image, just to try again to get input on my spherical-to-2d projection question!)

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Permalink Reply by Luis Fraguada on February 14, 2011 at 6:11am

Hey Chris,

Cool stuff, we are working on some similar stuff.  I found this from David on the newsgroup...not sure if it will be useful.  Check it out.

http://news2.mcneel.com/scripts/dnewsweb.exe?cmd=article&group=...

 

Best,

Luis

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Permalink Reply by Chris Wilkins on February 14, 2011 at 6:33am

On a related thread, I'm going to try to use the Parse XML component from gHowl to read KML files directly. (that's your project right?)

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Permalink Reply by David Rutten on February 14, 2011 at 7:25am

Freaky, I have no recollection of writing that at all. And yet it was only two years ago.

 

--

David Rutten

david@mcneel.com

Poprad, Slovakia

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Permalink Reply by Vicente Soler on February 14, 2011 at 8:11am

This is an extract from a definition i did some time ago to import Google Maps data into Grasshopper:

 

Dim x,y,la,fi As Double

la = xlApp.Worksheets(i).Cells(1, 3).Value * math.PI / 180  

fi = xlApp.Worksheets(i).Cells(1, 2).Value * math.PI / 180  

x = la    

y = math.Log(math.abs((1 / math.cos(fi)) + math.Tan(fi)))

ptl.add(New Point3d(x * s, y * s, 0))

 

It read longitude/latitude values from a spreadsheet and projected them in 2d. The "s" variable is just a scale factor. It was used just for display purposes, so it looked good enough for that (it matched an underlying pictureframe with a screenshot of google maps) but i don't really know how accurate it is.

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