Floor Plan Preparation for Wireless Design/Surveys

I’ve read and watched a lot of blogs, books, webinars, etc. that go into the process of preparing for a design or survey as follows:

  1. Obtain floor plans from client.
  2. Import into the design software.
  3. The rest of the process.

But none go into the step between 1 and 2. I have never received a floor plan that is ready to be imported into the software as is. It always has to be modified to some degree.

The purpose of this post is to outline that process. Keep in mind that I am no Photoshop expert so there are likely better ways of doing these things. If so, happy to hear it.

Software

I use the free, multi platform and open source equivalent to Photoshop, GIMP. Free version of Photoshop. ‘Nuff said.

In this tutorial, I’ll be using the Windows version 2.10.2.

Importing and Scaling

Start GIMP and then go to File > Open to import the floor plan. This can be any image file or PDF. If importing a multi page PDF, use the option to open pages as images.

PDF Import

Depending on the size of the original image, you may need to enlarge. You want to perform this here instead of simply zooming when the plan is imported into Ekahau/Airmagnet because they will blur the image. This looks bad when surveying/designing and worse, unprofessional, when presenting to clients in report or any other form. In GIMP, you can sharpen it.

First make sure that you are seeing the image as 100% zoom. I’ve made the mistake of enlarging images in the past that were at 25% zoom. View > Zoom > 100%.

Next enlarge the image. Image > Scale Image. You’ll see height and width values. Change either and press Enter. If the chain link image between them is solid (instead of broken) GIMP will automatically adjust the other value. Click the Scale button.

Now the image is likely blurry after that. Use Filters > Enhance > Unsharp Mask > OK. This will sharpen the image. If you think it is still a little blurry, Filters > Repeat “Unsharp Mask” to do it again. Edit > Undo if you don’t like the result.

The below images show the before and after of sharpening the map after enlarging it. Sharpen was performed twice. There is a small amount of artifacting but the result is significantly better despite this. A third sharpening further improved sharpness but significantly increased the artifacts to an unacceptable level.

Before sharpening
After sharpening twice

Cropping

You’ll need to crop around the building/area that you require. This removes unnecessary white space, out of scope areas and extraneous, blueprint related information. I usually leave a centimeter or two around the outer walls (assuming a building floor plan).

Crop tool

As can be seen below, the Crop tool allows a box to be drawn around the area to be cropped. The highlighted section shows the rectangular box that displays when placing the cursor near the outer sides of the box. Square when placing the cursor near the corners. When clicking and holding inside of this, the sides/corners can be resized.

Cropping

When finished selecting the relevant area, click inside of the box to crop the image.

Removing Colour and Shading

This is an important step. Colour plans are difficult to see under heatmaps. Heatmaps are difficult to see over shaded areas.

You want the floor plan to be black and white or greyscale for obstructions such as walls, doors, furniture, etc. Open areas (flooring) should be white.

Removing Colour

There are a few ways to do this but I get the best results from Colors > Desaturate > Mono Mixer > OK. Below illustrates the effect of Mono Mixer when applied on a section of the colour floor plan.

Desaturation

Edit from the future: An easier way than above is to go to Image > Mode > Greyscale.

Removing Shading

You want the Select by Color tool for this. Also set the background colour by clicking it and selecting white.

Select by Color tool

It might be difficult to see on your screen but the below section of floor plan is shaded a light grey.

Shaded floor plan

Click an area with the tool and it will select all areas with that colour. Press the delete button on your keyboard to remove.

All grey shading removed

Removing Unnecessary Components

The image above shows the bottom rooms with lines through them. You may also have other information such as arrows, labels, measurements, cable trays and the like cluttering the floor plan. The below image shows this.

Label Clutter

In the above screenshot for the Select by Color tool, the three icons on the line above from left to right are the Rectangle, Ellipse and Free Select tools. Use these to select items. Use the Bucket Fill tool and settings pictured below and click inside of the box to paint it white.

Bucket Fill tool

It’s a tedious process but gets the job done as seen below.

Label removed

Another option is simply using the selection tool and pressing the delete key. You’ll see a grey and black checkered pattern underneath which indicates transparency. The way around this is Layer > New Layer, select Fill with: White and OK.

This will place the layer in the foreground over your floor plan. Go to the Layers window, left click and hold on the new layer and drag it to the bottom underneath the floor plan layer.

White layer in foreground
White layer in background

Exporting

Once everything is complete, you need to save the image. Go to File > Export As. Save the file in the correct location and with the correct name. This includes the file extension as GIMP uses this to save the file accordingly. I use PNG. Click Export on both prompts.

Conclusion

Depending on the amount of changes required, this can be a 10 second or 10 minute job per floor plan. As I said above, if you know of better ways to do this, I’d really like to know.

Until next time.

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