Qgis - need to draw exact lines (mtrs) with fixed angle

Question

I use GIS 1.8.

I have the need to be able to draw exact lines and shapes on a bing map. (This is to project a yet to be build greenhous project on a map to show what i would look like).

I have found the tool of Olivier Dalang (improved polygon capture) to be very usefull, since this tool enables me to draw lines while specifying the exact length and angle of the lines, and by doing so i build all walls of the greenhouse on the map).

Here is my problem. The plugin enables me to enter the length in 'units', and drawing a line of 1000 units makes me come up with a line of about 622 meters.

I cannot find the exact way to change or find out how to draw in meters.

Any help highly appreciated!

(If there are other tools for drawing 90 degrees angled lines to a map I welcome these too!)

Answer 1

If you use bing map, you may use Openlayers plugin. The units of that are not real metres. They fit only at the equator, and get distorted the more to the poles you come.

Try the UTM projection designed for your part of the world to draw the building with cad tools.

If you don't have a suitable map in UTM projection, make a screen copy of the bing map with Save as picture, load it as raster file with EPSG:3857 as layer CRS, change the project CRS to your UTM, create the vector layer in the same CRS, and draw your building.

Then you can switch the project CRS back to EPSG:3857, delete the raster picture layer and activate the bing background again.

Answer 2

CadInput is a PROTOTYPE QGIS Python plugin that allows to numerically constrain the cursor to achieve efficient and precise digitizing, as possible in CAD packages, with any QGIS tool.

Visit: https://vimeo.com/85052231