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I have a plan of a building, drawn to scale in Corel Draw. The whole drawing was 'surveyed' using the principal of taking distances from of each of these 2 points to identify the location of a 3rd point - triangulation I think its called. I have spacial references for the 2 fixed and known points - not 3. If I had 3 points I could easily geo-ref a bitmap layer from the drawing, but I don't have that luxury.

How can I add this drawing?

When replying please consider I am really new to QGIS.

Thanks

  • Corel Draw can export to DXF - this dxf file can be loaded and georeferenced in QGIS. – Mapperz Mar 21 '14 at 13:41
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I guess you have the coordinates of the "known" two points, so you can add them as a point layer to QGIS. You can use the Openlayers plugin with Openstreetmap or Google background to see if they are placed correctly.

For the further work, delete the Openlayers layer, and choose a better projected CRS, like UTM for your part of the world.

If you only have distances for the local points (and no bearings), you can draw circles using the CAD tools plugin with those distances around your two points, and one of the intersections has to be the local point. Do the same for some other points

With that, you now have points to georeference.


You could do the same in Corel Draw as well:

Transform the coordinates of the known two points into UTM, draw circles with delt E and delt N around one of them, and you can construct lines of constant Easting and Northing as tangents on the circles and the other point. From these, you can calculate the UTM coordinates of the rest.

It should look like this:

enter image description here

The almost horizontal line should have a constant Northing of N2.

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  • Thanks - I understood abt intersecting circles - that's how I have drawn it using CDW, so I will have a go with the CAD tools. – tsrplatelayer Mar 23 '14 at 19:25
  • The bit abt transforming into UTM and using delt E and delt N - I'm sorry but as an absolute novice I didn't follow that at all. Project CRS is EPSG:27700. – tsrplatelayer Mar 23 '14 at 19:28
  • It should work with EPSG:27700 the same. Calculate the Eastern and Northern difference between the two known points, and draw the circles around one of them in Corel draw with these two radii. – AndreJ Mar 23 '14 at 21:34
  • I think I follow - this will allow my to calculate the locations of the other points in CDW so that I can add them to point layer? – tsrplatelayer Mar 25 '14 at 12:21
  • Yes, exactly what I ment. – AndreJ Mar 25 '14 at 12:32

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