1/x This morning I woke up to see viral maps incorrectly comparing the damage area of the Beirut explosion to London and New York. I have corrected the maps with a little thread to explain my corrections. img 1. tweet with my notes. img 2-4. my new maps. 
2/x The original map looks like it was made by the @DailyMailUK It's a pretty clear map... except for the fact there is no scale or distance indicated on it. (Thank you #gischat sleuths that helped me find the original).
dailymail.co.uk/news/article-8…
dailymail.co.uk/news/article-8…
3/x A curious and well intentioned person used an online tool that slaps circles onto google maps, but none of the maps show any distances or scale. And the google maps are, of course, projected in Web Mercator, which does NOT show distance equally across different latitudes.
4/x I picked the 10km radius by measuring the distance to the airport runways in the original map. The circles ignore all topography, while it looks like the actual damage stretched farther along the coastline and not as far inland, uphill(?).
5/x If you made it this far, you may already have noticed, my maps use azimuthal equidistant projections, centered on each POI, and are displayed in the same scale, so they can be compared. BECAUSE SCALE AND PROJECTIONS MATTER. Enjoy.
6/x A follow-up: 1) these maps don't model what the damage would be in other cities. They just help you visualize 5-10km using other cities for context.
2) Never heard of map projections before? Read about them here: arcg.is/0jDWmf
2) Never heard of map projections before? Read about them here: arcg.is/0jDWmf
