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Square Building Corners From Air Photo

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#1
mrfaize

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Hi,

I have a map where the source is a high resolution air photo. In Illustrator CS3 I need to capture the features including building outlines but want to maintain square (90 degree) building corners where appropriate. I don't want crooked buildings :)

Does anyone have any tips how to achive this other than drawing the building with horizontal and vertical lines then rotating the building into position. I have seen tools in GIS which can create lines at 45 & 90 degrees relative to the line I am constructing but couldn't find anything similar in AI. I'm checking the documentation.

Thanks in advance.

#2
Hans van der Maarel

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Maybe Hotdoor Cadtools can be of use? It's been a long time since I last used it, but since it brings CAD functionality to Illustrator (and this is something that ought to be possible in a CAD application) it might do the trick.
Hans van der Maarel - Cartotalk Editor
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#3
mrfaize

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Maybe Hotdoor Cadtools can be of use? It's been a long time since I last used it, but since it brings CAD functionality to Illustrator (and this is something that ought to be possible in a CAD application) it might do the trick.


Thanks Hans - an interesting solution as always!

Any other solutions from anyone else?

#4
sitesatlas

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Thanks Hans - an interesting solution as always!

Any other solutions from anyone else?


I don't want to sound like a broken record -- I feel like I should do promotion for the Institute of Cartography -- but their free Illustrator plug-ins include a tool for this very task. It is called Rectify Closed Paths and it squares off angles of polygons that are within the tolerance setting. The objects can be automatically rotated to align with a designated reference line and at a specified distance, so digitized building footprints can be rectified, aligned to a street, and offset a specific distance, for example. Check out the Word document in this thread: http://www.cartotalk...?showtopic=4070
Michael Borop
World Sites Atlas
http://www.sitesatlas.com

#5
mrfaize

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Thanks Hans - an interesting solution as always!

Any other solutions from anyone else?


I don't want to sound like a broken record -- I feel like I should do promotion for the Institute of Cartography -- but their free Illustrator plug-ins include a tool for this very task. It is called Rectify Closed Paths and it squares off angles of polygons that are within the tolerance setting. The objects can be automatically rotated to align with a designated reference line and at a specified distance, so digitized building footprints can be rectified, aligned to a street, and offset a specific distance, for example. Check out the Word document in this thread: http://www.cartotalk...?showtopic=4070


Thanks Michael. Only problem is that I'm using a Mac and the plug-ins only work on a PC I understand. May try an evaluation of Illustrator on a PC sometime to see if it's worth having both.

Edit - have just looked at your PDF English guide and I definately need to try this!

#6
mlbostwick

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Rick Johnson may have a Mac plugin that will do what you need. It's called Square-up.

http://rj-graffix.co...e/plugins.html#

#7
mrfaize

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Rick Johnson may have a Mac plugin that will do what you need. It's called Square-up.

http://rj-graffix.co...e/plugins.html#


Many Thanks! Very useful tool which I have decided to use.

#8
Dennis McClendon

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Preferences-->General-->Constrain angle

In FreeHand, this is in the toolbar. I use it all the time. A good example is a college campus where most of the buildings are oriented the same way—but not to the cardinal directions. Draw a line or rectangle and rotate it to match the angle most of the buildings are at, check to see what that angle was, set constrain, and then happily draw perfectly rectangular buildings using the rectangle tool.
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#9
mrfaize

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Preferences-->General-->Constrain angle

In FreeHand, this is in the toolbar. I use it all the time. A good example is a college campus where most of the buildings are oriented the same way—but not to the cardinal directions. Draw a line or rectangle and rotate it to match the angle most of the buildings are at, check to see what that angle was, set constrain, and then happily draw perfectly rectangular buildings using the rectangle tool.


Dennis,

Take a look at the plugin if using Illustrator - for 10USD it's a no brainer and you can try for free.

#10
Greg

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a very simple solution would be to just hold shift with the pen tool, it will constrain your next segment in 90 degree increments.

#11
mrfaize

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a very simple solution would be to just hold shift with the pen tool, it will constrain your next segment in 90 degree increments.


OK if your buildings are aligned horizontal / vertical. I believe that the angle is relative to the page (maybe the contraint angle setting) and not to the previously drawn segment (which I can do in a GIS).

And forget drawing them and then rotating into position.

For 10USD it's not worth even worrying about. In fact I spent 30USD and bought the productivity pack as some other tools looked interesting.

#12
Dennis McClendon

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But why buy a third-party plugin when the capability is already in Illustrator?

Preferences-->General-->Constrain angle
Dennis McClendon, Chicago CartoGraphics
chicagocarto.com

#13
Hans van der Maarel

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But why buy a third-party plugin when the capability is already in Illustrator?

Preferences-->General-->Constrain angle


Which works quite well actually... Enter a value there for the base angle and by holding the shift key while placing new vertices, you can restrain them to 45 degree intervals of that base angle (does that make sense?)
Hans van der Maarel - Cartotalk Editor
Red Geographics
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#14
mlbostwick

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I can see where the constrain angle capability in Illustrator would work if most of your buildings were at the same angle. But what if you had a lot of irregularly placed buildings? You would have to open the dialogue and enter a new constrain angle for each (not to mention estimating the angle each time). With the plugin you just roughly draw in your buildings, then select them and apply the filter.

#15
mrfaize

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I can see where the constrain angle capability in Illustrator would work if most of your buildings were at the same angle. But what if you had a lot of irregularly placed buildings? You would have to open the dialogue and enter a new constrain angle for each (not to mention estimating the angle each time). With the plugin you just roughly draw in your buildings, then select them and apply the filter.


Exactly! If the functionality exists in Illustrator, two different orgnaisations have created a plugin for no reason at all. :unsure:




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