I was approached by a community group to help survey a site they were planning to turn into a garden. Dense tree cover made drone photogrammetry impractical, while the size of the site meant surveying it on foot alone would be very time-consuming. This gave me an opportunity to experiment with a technique I had been formulating in my head, 'group walkover photogrammetry'. I developed the survey methodology myself and recruited three friends to help carry it out.

We walked across the site in a line, taking photographs at regular intervals using different mobile phones. I then combined the images into a single photogrammetric survey, producing a map that the group could use to plan the garden and calculate how much wildflower seed to purchase.

The approach worked surprisingly well, particularly given the different cameras involved. The main difficulty was maintaining a consistent camera height between volunteers. In future, I would use simple extensions such as selfie sticks and check image quality more regularly during recording.