Juxtapose – Comparing Images

Juxtapose creates a slider to compare two images. It’s one of several handy tools from the Northwestern University Knight Lab. This Juxtapose images compares London’s Heathrow airport in 1945 and 2014. (Link to larger version.)

What a great way to stimulate some class discussion around what’s changed and how the changes came about.

  • How was the 1945 image created? Were there satellites? Maybe not? Then how did they get the image?
  • Cool, the runways and ring road are still in the same place. Was there a smaller airport here first?
  • When did commercial aviation really take off, so to speak? Wasn’t it later than 1945?
  • Why did London start building such a huge airport so early? How long did it take?
  • So many farm fields disappeared? What happened to the farmers?
  • How big were the planes back then? Did they need that long a runway? Oh, the runway is longer in 2014. When did they expand it?
  • and on and on…..

Making a Juxtapose Image

This Juxtapose was created with screenshots from Google Earth, by zooming in on Heathrow and using the Windows Snipping Tool. Though any screen clipping tool will do. Google Earth has many historic image overlays and zoomed in on Heathrow, the oldest overlay was from 1945. The historical images are found by clicking on the clock at the top of a Google Earth screen, then using the slider to change dates.

google earth

The images need to be similarly sized to get the full effect. In Google Earth that’s fairly easy, just don’t zoom in or out between taking screen shots.

Since you can’t upload images in Juxtapose, upload them to cloud storage somewhere. I used Dropbox, but other tools will work too.  If you’re taking screenshots inside a browser, the Awesome Screenshot extension for Chrome, is, well, awesome. It connects to your Google Drive and easily uploads the images for you.

Then enter the URLs for the two images in the boxes on the Juxtapose page and you’re pretty much done. Link to or embed the resulting image.


  • Compare landscape/environment over time: lakes shrinking/growing, glaciers receding, volcanoes exploding, towns appearing out of farmland, etc.
  • Use current Google street views to compare with historic photos. (History Pin uses a similar technique for placing old photos over current views.)
  • Or get out in your own community and take photos from the same angles as historic photos to compare. Fun project for schools and public libraries. Reminds me a bit of an I Spy projects from many years ago. If we did that project today, this would be a fun way to update it.
  • What ideas can you add??