Measure with triangles

Making a plan for an irregular shaped garden can be tricky. Triangles, cosines and The Internet to the rescue

Outline of garden on graph paper triangulated with interconnecting triangles
If each point on the garden perimeter has 3 measurements coming from it, then you can calculate the angles

First off, a disclaimer. I’m shit at maths. Luckily, there’s clever people and the internet. I have a lovely design job at the moment and it has an irregular shaped rear garden.

The trick is to mark out (with small stakes if necessary) set points around the perimeter of the garden, and then make sure that there are 3 measurements from each point to other points (see image above).

If you know the three sides of a triangle, you can work out the angles in a triangle. Luckily, someone has made triangle-calculator.com, and if you can click on SSS you get to calculate “Side Side Side” triangles, with the click of a button:

Screenshot of triangle-calculator.com

Calculating angles from 3 known lengths of a triangle

Once you have the angles, you can use CAD software like QCAD, and re-create the triangle. This is fiddly and requires some CAD knowledge but totally doable (and the subject of a whole workshop in itself 😆).

Then you recreate the triangles, one from the other (hint, use duplicate and the Lines with given angle tool). When you’ve recreated all the triangles, rotate the whole outline to a known fixed point, which is usually the house. You can see, I’ve taken some measurements from the house in the first diagram, so that I can work from them.

CAD mesh triangle outline of garden

All recreated triangles rotate to fit to angle of the house

Finally, delete the lines in the centre of the garden, and you are left with an outline. I know, it’s tricky and not as easy tracing the outline of a satellite photo but it’s one way of getting a plan of a smaller irregular garden.

Finished outline of garden in CAD

At the end of all that hard work, you’re left with a few lines outlining your irregularly shaped garden

Good luck! And the next blog post will be more plant-based 😎 🌱

Author:
Date:
Permalink:
https://www.forestgarden.wales/blog/measure-with-triangles/

Subscribe to blog posts by email