Those cool sliders that show “before” and “after” images

I wanted to look at some satellite images from Hurricane Dorian, and I found a lot of them — specifically Grand Bahama and the Abaco Islands — up on Google’s big library of satellite images.

It was cool, because when I was for example searching on September 9, there were already images of the Bahamas posted that were captured on September 8. That is quite a quick response time!

I wanted to make a feature where you can slide back and forth between the before-and-after of Hurricane Dorian. I had heard about this new app called Flourish, and lo-and-behold: you can get a slider like that for free. You just have to create an account, and then you upload the “before” and “after” images you want to compare.

Here’s mine comparing Great Abaco Island from August 16 (before) to September 5 (after).


You can see that the storm has kicked up a lot of sediment in the water. If that sediment was leached from the land (it kind of looks like it; you can see curls of sediment smoking their way into the water) then that can have repercussions for the land surface of Great Abaco Island.

By the way, did you ever read the “Lost Girl” books? They were set on a deserted speck of the Abaco Islands.

Now, that is a comparison of two images that are just weeks apart in capture; so how about looking at changes in an island’s land surface over a few decades? I made another before-and-after slider image of Tangier Island in the Chesapeake Bay. The “before” image is actually from Landsat, and it is from 1992, so you see it looks quite a bit blurrier than the newer Sentinel-2 image. Times have changed, and so have satellites.

Looks like Tangier has lost quite a bit of ground; both in the north, and on that smaller eastern island. The spit of sand in the south has changed, too.

By the way, have you read “Jacob have I loved”? It’s set on a seemingly fictional Chesapeake island very similar to Tangier and Smith Islands. Oh, it is so good!



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