PinPoint is a data analysis service offered by Thelma Biotel for fine scale 2D and 3D tracking of aquatic animals tagged with our acoustic transmitters. Accurate position tracking, compared to traditional presence/absence tracking, gives extensive insight to the movement patterns of the species or object studied. The system is built on the principle of speed of sound in water, where synchronized clocks with millisecond precision and precise temperature sensors in our receivers (TBR 700) allow for extremely accurate positioning.

A PinPoint report will give you extensive analysis of the logging conditions, the system accuracy, and the x-, y-, and z-position of each tagged individual. 3D positioning will depend on whether the transmitters are equipped with a depth sensor or not. In most cases, the accuracy of 2D tracking is largely improved by depth information as well.


Positioning of fish or other aquatic animals is an effective and accurate way to study the animal’s behaviour and fine-scale migration patterns. PinPoint has been applied to a series of useful projects with results leading to positive measures. For instance, king crabs, an invasive species turning the sea floor into an uninhabitable desert in Northern Norway and Russia, has become a profitable resource for fishermen up north. In a fjord in Northern Norway, 70 king crabs were tagged over two years in order to monitor their exact movements, resulting in a strategy for optimized king crab fishing.

In another study, crayfish were tagged with acoustic activity tags and positioned using PinPoint in order to investigate the effect of chemical treatments used to eradicate invasive species. The combination of using an activity tag together with PinPoint positioning gives a through understanding of the animals’ behaviour and welfare before, during and after such processes.

Examples of other uses of the PinPoint positioning system include tracking of fish to help decide where to build fish passages, aquaculture, and monitoring subsea constructions and equipment.

How it Works

PinPoint is based on the positioning principle of time difference of arrival (TDOA), also known as multilateration. TDOA is a way of determining the position of a transmitter based on known locations of receivers and the difference in time that it takes for the signal to travel to each of the receivers. The arrival time of each emitted signal will depend on the distance between the transmitter and each receiver. Between two receivers, there will be an infinite number of possible locations, and the solution space will look like a hyperboloid. In order to find the position of the transmitter in the solution space, a third receiver is needed to find the intersection of the two hyperboloids. If the animal is tagged with a pressure sensor as well, the results will be more accurate, also allowing for 3D-tracking.

For PinPoint to work, the receivers need to be deployed so that the distance and angles between each receiver form equilateral triangles, like shown in the illustration below. The blue circles around the equilateral triangles show where the tagged animal needs to be in order to get the most accurate tracking results.

What You Get

With the PinPoint positioning system, you will get a good introduction in how to set up the receiver grid. Often it begins with a small trial to make sure you obtain the best possible data when deploying the entire grid. Following this, we will assist you in determining how and where to deploy the receivers. Once the data is collected, we do extensive analysis of your results and run them through our positioning algorithms. This results in a report containing an analysis of the environmental conditions, such as the speed of sound in the deployment area and background noise conditions.