When we decided to go back to a Marengo neighborhood ravaged by a natural gas explosion on June 11, 2017, to compare how the area looks now, it wasn't as simple as launching the drone.
To accompany an article about the anniversary, we were looking for the same view shown in photographer Mark Welsh's photo a year ago in the immediate aftermath of the blast. That meant our drone had to go to the same spot.
The drone app we use along with Photoshop, our photo editing software, can tell us the altitude and GPS coordinates where a photo was taken. With this information and a copy of the original photo, photographer Brian Hills was able to shoot from very nearly the same position as a year ago.
With before and after photos of the scene in hand, we turned to a tool called Juxtapose, developed at Northwestern University's Knight Lab. With careful planning, Juxtapose allows someone to see two photos side by side, with a slider in the middle allowing online viewers to quickly move between then and now.
To prepare the photos to be juxtaposed, the two images are brought into Photoshop, where the latest image is set on top of the older image. We use common items in the two photos -- such as the corner of a roof or position of a fence -- to further tweak and match up the two images.
Then, the files are cropped to be the same size, each image is saved as its own file, and the two files are uploaded to Juxtapose, which handles the hard part of coding and creating the presentation.
The final step is taking the generated Juxtapose and embedding it in a story, like this:
"We're proud to have international adoption, and beyond being useful to journalists, we see educators, students and all kinds of other folks using them," he said. "Just today I was answering a support question from a county planning official from a mid-Atlantic state, and we once had a TimelineJS bug report from Secretary of State (John) Kerry's office."
Here are some other ways that the Daily Herald has used Juxtopose:
1) To show the aftermath of the Marengo explosion.
2) To show how late spring arrived this year.
• Jeff Knox is Daily Herald senior director of visual journalism. Tim Broderick is editor of data journalism and graphics.