How To: Density Maps in Tableau
1. Create calculated fields for the rounded latitude and longitude.
2. Drag the rounded latitude and longitude on to the rows and columns shelves. Make sure that both are continuous dimensions. Set the mark to square and the size in the middle.
4. Finally, bring the worksheet into the dashboard and size appropriately. I used 1050 by 550 to get the sizing I liked.
That's it! Feel free to comment with questions or download the workbook.