The challenge
Mussel App is farm management software for New Zealand mussel and oyster farmers. Harvested mussels were measured one by one with callipers. It was slow, and two graders would often get different results.
The goal
Turn one phone photo of mussels on a measuring plate into length and width in millimetres, reliable enough for grading and simple enough for use on a boat.
What we built
- A YOLO model finds and outlines every mussel in the photo.
- A second model reads the ruler printed on the plate, so pixels convert to millimetres on every image, at any distance.
- Each shell is measured and the results are drawn back onto the photo for a quick check.
- Everything is served through a FastAPI service on AWS Lambda, ready for the iOS app.
The hard parts
Photos taken from different distances.
Calibration from the plate's own scale in every photo.
Phone rotation and EXIF quirks.
Automatic orientation correction before any measurement.
Busy steel benches in the background.
Directional filtering to isolate the ruler lines.
Blurry or partly hidden shells.
A fallback that still estimates size and marks low confidence results.
The result
Consistent, hands free mussel sizing in seconds, replacing manual calliper work for the team.