Lorna Brown provided a refresher on map layers and spatial calculations for the #WOW2022 challenge this week. You’ll need Tableau Desktop v2020.4 or later to complete this due to the functionality incorporated.

The data set provided contains rows of origin & destination airports including the latitude and longitude values for each.

I found there were some fields in the provided data set which I don’t think should have been there. It meant when I came to naming some of my fields, I had to be more creative due to the existing ones.

We’ll start off by setting up the calculations required.

Firstly we need to create a spatial object out of our Origin and Destination airports.

Origin

MAKEPOINT([Origin Latitude],[Origin Longitude])

Destination

MAKEPOINT([Destination Latitude],[Destination Longitude])

Next we’re going to need to have a line to connect these

Origin-Dest Line

MAKELINE([Origin],[Destination])

We’re going to need ‘buffer’ to define the circle displayed. The size of this is to be defined by the user, so we’ll need a parameter

pBufferSize

integer parameter defaulted to 1000

and with this, we can then define the buffer

Buffer from Origin

BUFFER([Origin],[pBufferSize], ‘miles’)

Finally we need to determine whether the destination airport is within the buffer ‘zone’.

Within Buffer

[Distance (Miles)]<=[pBufferSize]

Note: Distance (Miles) already existed within the downloaded data set. I was expecting to have to calculate the distance myself, given the nature of the challenge. If I had had to create it, I would have used the calculation DISTANCE([Origin], [Destination], ‘miles’)

This is all we need to build the viz. I’m going to start from the top – down ie Origin airport -> Destination airport -> Lines – >Buffer.

On a new sheet, add Origin Airport to Filter and set to LAS. Also add Within Buffer to the Filter shelf and set to True.

Then drag Origin onto the main canvas area and drop it when you see ‘Show Me’ displayed on the cursor. This will automatically add all the required fields into the relevant locations

Change the mark to a circle, increase the size and set the colour to black. Add Origin Airport to Label and Origin Name to Tooltip, and adjust the tooltip accordingly.

This is the first map layer.

Now drag Destination onto the canvas and drop it on the ‘stacked layer’ icon when you get the Add a Marks Layer option appear

This will create a new marks card on the left, and is the 2nd marks layer.

Add Destination Name to the Detail shelf, then change the mark type to square. Add Destination Airport, Origin Airport and Distance (Miles) to Tooltip and adjust tooltip to match.

Finally move the Destination marks card so it is below the Origin marks card. Click on the Destination card and drag to below the Origin card and drop when you see the orange line appear

Now drag Origin-Dest Line onto the canvas and drop it on the ‘stacked layer’ icon when you get the Add a Marks Layer option appear to create the 3rd marks layer. This will add all the ‘spokes’.

Change the colour to grey. Add Destination City to the Detail shelf. Add Origin Name, Origin Airport, Distance (Miles) and Destination Airport to the Tooltip and adjust accordingly. Finally, drag this marks card so that it is now below the Destination marks card.

Final layer now – the buffer zone.

Drag Buffer from Origin onto the canvas and drop it on the ‘stacked layer’ icon when you get the Add a Marks Layer option appear to create the 4th marks layer. Adjust the colour to light grey, and reduce the opacity to suit. Then move this marks card to the bottom, so its beneath the Origin-Dest Line marks card.

And that’s it. Add the sheet onto a dashboard, and show the Origin Airport filter as a Single Value dropdown so only 1 origin airport can be selected at a time. I also customised the control so the All option did not display either. Add the pBufferSize parameter to the display too, and test the viz by changing the size and the airport.

My published version of the viz is here.

Happy vizzin’!

Donna