Whenever I share images from Curiosity, among the most common questions I’m asked is “what is the scale of this image?” I wish I could answer those questions, but it’s not straightforward to do for Curiosity because the scale of any feature in a picture depends on its distance from the rover, a number we don't know; moreover, the scale changes throughout the image, with some objects being much closer than others. (This is in contrast to, say, Cassini images, where the targets are extremely far away from the orbiter so the scale is pretty constant across the image, and we usually know the distance to a target, so it's simple math to figure out the scale of a photo.)
One way to figure out the scale of topographic features visible in Curiosity pictures is to identify the same features in orbital images, compute the scale from the (known) scale of the orbital photo, and draw objects of familiar scale into the Curiosity pictures. It takes a bit of work, which is why I almost never go to the trouble.
The particularly picturesque images of the Murray buttes that Curiosity has been taking lately have inspired a lot of people to wonder how big they really are. So I'm extremely grateful that space imaging enthusiast Seán Doran has finally answered that question for us in a striking way, by dropping a simulated image of an astronaut into many recent Curiosity panoramas. Enjoy!
Look for more of these photos on Seán's Flickr page. Seán tells me the astronaut’s name is Astrid, and that her explorations are not finished. “She's covered most of Murray buttes already with previous sites to follow!”