[postgis-users] depict a polygon using cross hatching

[Michael Welter]

Hello George,

I'll be using Google maps on an Android phone to display the polygon with the cross hatching.

Mike

On Jun 3, 2011, at 2:21 PM, George Silva wrote:

> Hello Mike,
> 
> What kinda of software will be used to do this?
> 
> Most GIS softwares can depict line hatchings without needing it physically exists on the database. Each line of the hatch has a special meaning for you or no?
> 
> If so, you should consider using a proper style, that will do that without giving you headaches to create the hatches.
> 
> George
> 
> On Fri, Jun 3, 2011 at 3:17 PM, Michael Welter <mike at introspect.com> wrote:
> Hello,
> 
> I have a polygon (with interior holes) that I would like to depict on a map using diagonal lines.  I don't suppose there's a ST_ function for this  :-)
> 
> Thinking out loud, I should derive the bounding box of the polygon, divide the top and right edges into equidistant points.  From the top points draw 135° vectors, and from the right points draw 225° vectors to the other side of the box.
> 
> Now the hard part:  for each line, determine the point where it enters the polygon and the point where it exits.  Also, where it enters an interior hole and where it exits.
> 
> The actual drawing on the map happens on a client computer (without postGIS), so the desired result from postGIS would be a list of line segments.
> 
> Does anyone have any ideas on this?
> 
> Thanks,
> Mike
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> 
> 
> -- 
> George R. C. Silva
> 
> Desenvolvimento em GIS
> http://geoprocessamento.net
> http://blog.geoprocessamento.net
> 
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