Hi Phelis. This can be done using a Union. I'm not sure which version of Tableau you're using, but I created this solution in Tableau 9.3. Here's what I did.
1. Copied all the rows from market_bids into a second sheet in the market_asks workbook
2. Titled that first blank column in both sheets 'id'
3. Created a new Tableau workbook, connected it to market_asks and clicked New Union at the bottom of the Sheets list
4. Dragged both market_asks and market_bids into the window and clicked OK. Notice how the Sheet and Table Name columns are automatically generated
5. Clicked on Sheet 1, right-clicked id and selected Convert to Dimension
6. Dragged lon and lat into the view, dragged id to detail and Table Name to color
Book7.twbx 45.9 KB
This worked perfectly well. Exactly what I've been looking to do for days now. Thank you so much for your help. Much appreciated.