Improved Polygon Capturing is a QGIS Python plugin, that allows to digitize new polygons or lines with predefined edge lengths and angles, as you would do in a CAD program.
It is based upon Improved Polygon Capturing authored by Adrian Weber.
The plugin adds a new icon to the digitizing toolbar.
Select a polygon or a line layer and toggle editing by clicking on the new icon.
A Dockable palette will appear.
From now on, you can enter the distance or the angle numerically in the edit fields. You have to check the "Lock" checkbox to actually lock the distance and/or the angle. Unlocked fields are entered using the mouse (which takes snapping into account).
You can also switch between absolute angle or relative angles (relatives angles are relative to the last line segment) by checking the "delta" icon.
Similar to the standard editing tools, left mouse clicks add new vertexes while right mouse clicks finish the geometry.
After finishing a new geometry the feature form opens and attributes can be entered.
The following shortcuts are available:
The plugin calculates the distance in plain trigonometry. Thus it is not recommended to use it in unprojected systems like EPSG:4326.
Please send bugs and ideas on the issue tracker : https://github.com/olivierdalang/improvedpolygoncapturing/issues
Or send me some feedback at : olivier.dalang@gmail.com
Improved polygon capturing plugin has been initially developed in June 2010 for a land management and registration project in the Lao PDR by Adrian Weber.
It was used to digitize land parcels with known edge lengths from high-resolution satellite images. The parcel edges have been measured a priori in the field.
Help is welcome ! There's a serie of issues and ideas on the github repository : https://github.com/olivierdalang/improvedpolygoncapturing.git