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I am running QGIS 1.7.0 on Mac OS X 10.6.8. When creating a polygon, how do I do it so that the lines are straight (90, 0 degrees, etc.) and when I create corners they can be right angles? For instance, how do I create a perfect square or rectangle? Thanks.

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up vote 13 down vote accepted

Check the CadTools plugin. It offers orthogonal line tools.

enter image description here

This screencast titled "Orthogonal Digitizing" should be of special interest for you: (this video is not longer available, see @Kurt's link to the tutorial)

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this is great, thanks! – hpy Aug 30 '11 at 17:42

the CadTools plugin should do what you want. there is also an tutorial: (especially look under "orthogonal digitzing")

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The Orthogonal Digitizing tool is still drawing vertexes exactly where I point. My CADTools version is 0.5.9 and QGIS version 1.8. I've tried it with Windows 7, Ubuntu 12.04 and Ubuntu 10.04 now, both with and without OpenLayers Bing Aerial to digitize from. The tutorial site is an excellent resource with a video showing a user clicking the tool, then digitizing a square with perfect 90 degree angles locked in. Could someone else make an attempt to see if it works for them? Sorry it took so long to get back on this. – user12711 Nov 19 '12 at 0:13
SOLVED: "You have to press the ctrl key to draw lines or polygons with square angles." [ I watched the video but didn't read the instructions. Lesson learned ] Thanks again. The CadTools tutorial link is great – user12711 Nov 19 '12 at 1:47
@user12711: if answer was useful, please accept by checkmarking – Kurt Nov 19 '12 at 7:48

Another solution is you use the plugin azimuth and distance.

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