How architects can survey and accurately draw complicated elevations with just one measurement

How architects can survey and draw a complicated elevation like this by taking just one measurement. In 4 easy steps.

Visit www.buryassociates.co.uk/elevation for a full tutorial & software download links.

What you’ll need is:
Some free to download software called Meshroom & CloudCompare
An ordinary camera
A tape measure
A CAD program

Before you start make sure image stabilization is turned off in your camera and remember not to change the zoom settings while shooting your photographs.

Step 1 - Take photographs of the facade and just one measurement

Start at one end of the building standing far enough back so you can see as much of the facade as possible.
Take a series of photographs of the entire facade making sure that each one overlaps the next by at least 50%.
Move along a few paces and repeat the process. Keep moving along taking a new series of photographs from each position until you reach the other end of the building.
Measure a distance between 2 features on the facade. The longer the distance, the more accurate your survey will be.

For this project around 40 photographs in total were taken from 5 different positions.

Download and install Meshroom and CloudCompare. There will be a link at the end of this video telling you where they can be downloaded from.

Step 2 - Use Meshroom to process your photographs into a 3D model

Drag & drop your photographs into Meshroom.
Save your project then process your photographs into a 3D model by clicking on the Start button.
A project of this size will take around one and a half hours to process.

Step 3 Use CloudCompare to turn your 3D model into an ortho image

Browse to your Meshroom project folder, open the Meshroom Cache folder and then the Texturing folder. There will be a folder in Texturing that will contain your 3D model in OBJ format along with some other associated files.
Drag & drop the file called texturedMesh.obj into CloudCompare.
Hold down the left mouse button and rotate the model so the view approximately shows the elevation correctly.
To reset the rotation point click on the + icon then double click on the point on the model that you want to rotate around.

Click on the Set current view mode button and select Orthographic projection.The right mouse button can be used to pan and you can zoom in and out using the scroll wheel.
Select texturedMesh in the explorer tree.
Select the Pick 3 points to make a cloud or mesh ‘level’ icon.
Identify a long horizontal line such as a brick course on your model.

Select a point near the left hand end of that line then another towards the right hand end.
Select a 3rd point on the same face as high as possible above the other 2 points.
Pan and zoom so your model fills the entire view.
Click on the Top View icon to make sure your view is still orthogonal.
Select Display then Render to file from the top menu.
Choose a file name and a location to save it. Set Zoom to 4, make sure both boxes are checked and press OK to create your ortho image.

Step 4 - Creating an accurate CAD elevation drawing from your ortho image
Open a new drawing in your CAD program and create a separate layer for your ortho image.
Make the image layer active and import or attach your ortho image.
Scale your ortho image so it’s the correct size using the measurement you took on site.
Lock the image layer and set the layer you want to draw in as active.
Use your normal CAD functions to draw over the ortho image to create your accurate elevation drawing.

We hope you’ve found this video helpful.
For a full tutorial and software download links please visit
www.buryassociates.co.uk/elevation.

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