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By hello@growdigital.org (Jake Rayson) on Nov 22, 2019 06:11 pm |
As part of my online forest garden course, I’ve been looking at how to use a screenshot of a satellite photo as the basis of a forest garden plan. If you’re comfortable with computers, the process is relatively straightforward. |
Using a CAD plan, it’s easy to move trees around to try out different ideas. The hard bit is setting up the boundaries of the land in the first place. |
The easiest way I’ve found to achieve this is to take a screenshot of a satellite photo and scale it down to the right size in the CAD software. |
This walkthrough will show you the 4 steps of importing and scaling the image. |
What you need |
A copy of QCAD, Computer Aided Design software that is Free and Open Source. There’s a free version which is absolutely fine for our purposes. In the demo, we’re using metres as the unit! A bitmap editor like Photoshop. GIMP is a Free Open Source alternative.
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1. Take a screenshot of your satellite image |
Use Google Maps, Apple Maps or Bing Maps and get the highest resolution satellite image of your land that you can. Make sure to include a metres scale (this demo is in metric!) Take a screenshot Open in your image editor and save as a JPEG in the same folder you’ll save your CAD file.
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2. Measure pixels per metre |
Using the rectangular marquee tool and measure the metres scale. In our example, there are 210 pixels per 30 metres. 210 divided by 30 equals 7 pixels per metre
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3. Calculate image scale factor |
QCAD imports images in at 1 pixel per 1 metre. In our example, we want 7 pixels per metre. So, we divide 1 by 7, which gives us 0.142857143
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This is the image scale factor, ie how much we need to scale the image once it’s in QCAD. |
4. Scale the image in QCAD |
Hop into QCAD, save a new file in the same folder as your background image Choose File → Import from the drop-down menu, then import your image Select your image with Select → Select All Bring up the Property Editor with View → Property Editor Enter the image scale factor (our example is 0.142857143) into both the Width Factor: and Height Factor: fields
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You’ll see the image scale down. And now you can use the Circle tools to create circles of a set diameter, which will represent trees. You can find the approximate height and diameter of common forest garden trees and shrubs from the brilliant Plants For A Future. |
If you found this tutorial helpful, please sign up to my newsletter for information about free forest garden mini-courses and resources. |
I made a short, unedited video of this process which you can view here: |
And the slideshow is online here: |
www.forestgarden.wales/wildlife-forest-garden/plan |
Happy forest gardening! 🌳 💚 |
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