Range Test Tags
Range tests are carried out after the initial setup of the study area as a part of the planning and documentation of the site. Special test tags, of similar transmitting power to the ones which is going to be used in the study, should then be deployed or towed at various locations and depths in the area in order to map the reception. This way possible dead spots can be detected and a measure of the effective water volume under study can be documented. The actual range of each hydrophone is affected by many different factors, and will vary through the study period, but an initial range test can help you to reposition or adjust the setup in order to maximise the quality of your data. In many cases scientific paper reviewers will demand a range test as a part of the quality assessment of the data. Remember though, that any given range test is only valid for the specific set of acoustic conditions at the time. As with all tagging studies it is really just the data you actually get you can build your discussion upon. There are too many unknown variables influencing to be able to conclude on the eventual tags, where you get little or no data. A properly conducted range test could help you discover, and mitigate, if you see blind spots in your receiver array where your tags might slip through undetected.
Our special range tags are coded as a sensor tag and will transmit a cyclic sensor value which then easily lets you document when you are reaching the limits of the reception range and transmits are starting to get lost.
The transmit period can be set up with a minimum transmit interval of about one code every 4-5 seconds for a setup where you will only have this tag in the system when you are performing the range tests. Then you don't have to worry about it transmitting all the time and potentially jamming up signals or getting code collision from other tags present in the system. This kind of tags should be used with great care as they will also jam up your system permanently if they are lost within the system. We can build in a timer which shuts the tag off after a set period of time, if you'd like to make sure to avoid this. If you would like to use several range test tags at the same time in order to get the range test done faster, we can set your transmit periods accordingly to fit your needs.
In order to monitor the changing conditions in your system and get a measurement of the overall receiver network efficiency over time, a set of fixed tags could be deployed at different locations during the complete data sampling period. Tags for synchronizing the clocks of receivers in a grid for 2D or 3D positioning will be used in the same way. This kind of tags should operate on a separate frequency or be coded with a transmit period which is adapted to the number of other tags which is likely to be active in the system at the same time.