I used SnakeMeasurer (Apps). Simply put, throw the snake in a box with something for scale, take a picture from above, import the picture into the program, set the length unit by measuring the object in the picture, then just start to measure the snake.
Here's an example photo:
The brochure is 21.0 x 29.7 cm, i.e. A4.
"bing bing bang a bang a bang bing bong bing a bing bang a bong
binga bing a bang a bong bong bing bong bing banga bong"
They've grown about 5cm between each shed. I would have included the third and fourth sheds, but I couldn't tell which shed belonged to which snake anymore.
"bing bing bang a bang a bang bing bong bing a bing bang a bong
binga bing a bang a bong bong bing bong bing banga bong"