How does tracking work

HOW DOES PHOTO IDENTIFICATION WORK

The same way ringing a bird or attaching a radio tag to a shark can allow people to find out where they are at any one moment in time, a photograph if analysed carefully can do exactly the same and it has the advantage of being largely non-intrusive.

Photo identification has been proven on many species, from South African penguins, to whale sharks. It uses visible marks on the animal which allows it to be individually identified, akin use of fingerprints to identify criminals.



Software similar to that used in astronomy is used to map the locations of the spots on the front of the penguins. These coordinates are saved and can be compared on a database.

The Green Turtle is identified by comparing the numbers, sizes, and orientation of the scutes on the sides of their heads. Other methods exist that involve mark and recapture of the animals which is obviously more intrusive that a mere photograph.

As you can see, the marks can be pigment variation the animal was born with or permanent marks caused by anything from catching prey or fighting.

If you look at the photographs below of the fins of the short-finned pilot whale it is easy to see which fins match.

1	2

3	4

If you look carefully at the above photographs you can see that photo's 1 and 4, are of the same individual as are 2 and 3. The differing angles, sea states, directions of movement, light conditions and photo quality can make it a difficult and often time consuming process to identify them. If would be easier if you could take out these variables as seen below.

These days there is a range of pieces of software which promise to aid this process, all have some benefits and disadvantages over each other. They all share 2 main tings in common, firstly they speed the process of comparing photos from a large catalog enormously, and secondly they all rely upon the user to make the final decisions as to individual matching photos.