Overview
Hydrophone Array
Overview
NEW Array localisation system !
PAMGuard users are deploying more and more complicated arrays and may now be working with some hydrophones deployed from a vessel while others are on free floating buoys. Other users are adding heading, pitch and roll sensors to their systems.
To cater for these developments the array management and localisation system has been substantially updated so that arrays containing multiple types of streamer / buoys, etc. can be effectively managed.
Within the PAMGuard framework, an “Array” refers to all of the hydrophones currently in use and only a single “Array” is loaded into memory and used at any one time.
An array may contain multiple “Streamers” or clusters of hydrophones. Hydrophones within each streamer (or cluster) are assumed to be connected to one another in some way and have a common origin. Within this context a moored or drifting buoy should be considered as a streamer. The streamer origin will generally be referenced to the vessels GPS position, or a fixed Latitude and Longitude.
Each streamer has a Hydrophone Locator system. This tells PAMGuard how to calculate the actual positions of the individual hydrophones from the streamer origin. Moored hydrophones generally use a rigid locator, whereas towed hydrophones are usually better off using a threading hydrophone locator which will give more accurate hydrophone positions as the vessel turns a corner.
A single array can mix streamers of different types.
Several different arrays may be managed and stored, although only one is loaded at any one time.
Each array may contain up to 32 individual hydrophone elements (transducers).
A one-to-many relationship exists between hydrophones and software channels.
Each hydrophone element must be assigned to a streamer. The actual coordinates for each hydrophone used by PAMGuard are the sum of the streamer coordinates and the individual hydrophone element coordinates. Although this appears to introduce some redundancy regarding the coordinates of each hydrophone, streamer assignment is important for two reasons. Firstly, it allows the errors on the relative locations of pairs of hydrophones to be more accurately defined (the errors between hydrophones in different streamers will generally be greater than the errors on a hydrophone in the same streamer). Secondly, should a streamer be moved or shortened, it is easier to adjust the coordinates of a single streamer than to adjust the coordinates of all hydrophones individually.
The Default Array
The first time you run PAMGuard, a default array consisting of two hydrophone elements spaced 3m apart at 5m depth, 100m and 103m astern of the vessel. Channels in the array are mapped 1:1 to ADC channels 0 and 1.