Comments on: Map Projection in ActionScript

By: Chen

Chen — Mon, 21 Nov 2011 23:47:15 +0000

I use Proj4 libray in my C++ project, when i try to use this AS3 version i found some projection types were removed, like Transverse Mercator, any ideas about this?

Thanks

Chen

By: Rendering SVG Country Maps in Python — vis4.net

Rendering SVG Country Maps in Python — vis4.net — Wed, 26 Oct 2011 09:30:23 +0000

[...] Therefore, I would have to port parts of the PROJ.4 code to JavaScript, which is something I've done before in ActionScript and actually don't want to do again. Instead, I found a nice and simple Python implementation of [...]

By: Chris

Chris — Wed, 29 Sep 2010 05:52:06 +0000

I was getting incorrect values from your Robinson Projection so I wrote my own and open sourced the code at:
http://www.flashmap.org/robinson-projection-in-as3-gpl/

By: Tutorial: Rendering a World Map in ActionScript | vis4.net

Tutorial: Rendering a World Map in ActionScript | vis4.net — Thu, 16 Sep 2010 11:06:09 +0000

[...] we must chose and initialize a map projection. I’m using the Wagner V projection of the as3-proj library. var projection:Projection = new Wagner5Projection(); [...]

By: Chris

Chris — Sun, 25 Jul 2010 04:25:09 +0000

Gregor,
Thanks for the quick response and link to the tutorial. I ended up writing my own Robinson projection function in AS3 which it looks like was a duplication of work but definitely helped make me more familiar with what was going on.
Chris

By: Gregor

Gregor — Fri, 23 Jul 2010 11:21:23 +0000

Hi Chris, Yoh have to multiply every projected y-coordinate by -1 before drawing. Assumedly the projection fomulas weren't designed for screen output but for print output and thus refer to a mirrored coordinate system. The tutorial I mentioned is already there, you can find it here.

By: Chris

Chris — Thu, 22 Jul 2010 20:48:43 +0000

Thanks for your work on this! I'm working with the Robinson projection and I'm confused why the sign of the X/Y coordinates differ from the sign of latitude and longitude. For example:

(-180,90)= (log,lat) in RobinsonProjection
(x=-125066398.48278639, y=-751566.9221849588)

Aren't the X/Y coordinates also starting from an origin at the central meridian and the equator? Shouldn't the sign for y and latitude be the same?

Also...if you get the chance to post that tutorial it'd be a life saver here too.

By: vtstarin

vtstarin — Sun, 25 Apr 2010 13:00:22 +0000

Thank you Gregor.

I still can't work around how is it done?. A short tutorial would be really my life savior.

By: Gregor Aisch

Gregor Aisch — Sat, 24 Apr 2010 19:24:42 +0000

I use the DataView class. The constructor takes two rectangles. The first is the bounding box of all projected points (you have to iterate over all projected coordinates and store the minimum and maximum values of x and y). The second rectangle is your target screen area. By the way, I'll publish a short tutorial showing this procedure in the next few days.. regards, Gregor

By: vtstarin

vtstarin — Sat, 24 Apr 2010 16:55:22 +0000

Hi Thanks for porting PROJ.4 to as3.

For eg
(-180,90)= (log,lat) in RobinsonProjection
(x=-125066398.48278639, y=-751566.9221849588)

How can you I convert this X Y mapping coordinate to X Y pixel coordinate for Image (3600x1800 pixels)?

Thank you again for your time and effort.