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Author Topic:   Evaluating Performance of SONAR

jimh posted 09-22-2010 08:54 AM ET (US)
What methods can be used to evaluate the performance of a SONAR with regard to sensitivity and ability to separate targets?
Hoosier posted 09-23-2010 09:00 AM ET (US)
It's damn hard to do with the HDS unit, they have too many user selectable parameters. You really need a stable water environment (test tank) and a very disciplined test plan to determine optimum settings. Once you put the boat in the water the water conditions will change and you have to start over...
jimh posted 09-23-2010 11:40 AM ET (US)
I was thinking of making a test course, and then running the boat over the course to obtain test results. The test targets would be something of known size and distance from the bottom.
A target could be a ping-pong ball or two or three, held off the bottom in a mesh net. Or perhaps a small air-inflated plastic ball. I guess the depth could not be too great or the ball might get crushed with water pressure. The balls could be tethered to an aluminum ladder. Lower the ladder to the bottom, mark its position with a float. Run the boat over the target and see what the SONAR shows. This would be a controlled target. You could attach a number of targets at different depth to the ladder rungs.
This test would be best done in a lake, where there was a sandy bottom about 30-feet deep.
6992WHALER posted 09-23-2010 12:44 PM ET (US)
Jim it would have been interesting to have rafted our two boats together in McCargoe Cove (with all the fish hits), to compare the reading and screens of the two different brands. If Homeaside had a third brand it would have been interesting to see if they all agreed or if there was a noticeable difference. Not the most scientific but might have been an easy way to at least see if all the units saw the bottom the same.
crabby posted 09-23-2010 05:09 PM ET (US)
Try a fishing pole or two rigged with different sized lures, sinkers, or whatever you'd like. This will only work in a static environment (not running). You should be able to see your lures dropping down and possibly be able to determine how far from the boat (sideways, or fore/aft) you are able to detect them.
On my old Lowrance 332c I am able to discern between a one ounce jig and the teaser tied two feet above it when dropped directly below my transducer in about 30 feet of water.
jimh posted 09-23-2010 05:34 PM ET (US)
Crabby--That is a good idea. It certainly is simpler than my test course approach.
SJUAE posted 09-24-2010 02:22 AM ET (US)
I my try something similar to confirm my structure/down scan is reporting port and starboard correctly. As the installation instructions implied that the transducer cable should be away from the stern, which seemed strange to me. The HDS units has a menu setting to allow the readings to be reversed, so no problem if it is initially set up wrong.
Regards
Steve

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Author	Topic: Evaluating Performance of SONAR
jimh	posted 09-22-2010 08:54 AM ET (US) What methods can be used to evaluate the performance of a SONAR with regard to sensitivity and ability to separate targets?
Hoosier	posted 09-23-2010 09:00 AM ET (US) It's damn hard to do with the HDS unit, they have too many user selectable parameters. You really need a stable water environment (test tank) and a very disciplined test plan to determine optimum settings. Once you put the boat in the water the water conditions will change and you have to start over...
jimh	posted 09-23-2010 11:40 AM ET (US) I was thinking of making a test course, and then running the boat over the course to obtain test results. The test targets would be something of known size and distance from the bottom. A target could be a ping-pong ball or two or three, held off the bottom in a mesh net. Or perhaps a small air-inflated plastic ball. I guess the depth could not be too great or the ball might get crushed with water pressure. The balls could be tethered to an aluminum ladder. Lower the ladder to the bottom, mark its position with a float. Run the boat over the target and see what the SONAR shows. This would be a controlled target. You could attach a number of targets at different depth to the ladder rungs. This test would be best done in a lake, where there was a sandy bottom about 30-feet deep.
6992WHALER	posted 09-23-2010 12:44 PM ET (US) Jim it would have been interesting to have rafted our two boats together in McCargoe Cove (with all the fish hits), to compare the reading and screens of the two different brands. If Homeaside had a third brand it would have been interesting to see if they all agreed or if there was a noticeable difference. Not the most scientific but might have been an easy way to at least see if all the units saw the bottom the same.
crabby	posted 09-23-2010 05:09 PM ET (US) Try a fishing pole or two rigged with different sized lures, sinkers, or whatever you'd like. This will only work in a static environment (not running). You should be able to see your lures dropping down and possibly be able to determine how far from the boat (sideways, or fore/aft) you are able to detect them. On my old Lowrance 332c I am able to discern between a one ounce jig and the teaser tied two feet above it when dropped directly below my transducer in about 30 feet of water.
jimh	posted 09-23-2010 05:34 PM ET (US) Crabby--That is a good idea. It certainly is simpler than my test course approach.
SJUAE	posted 09-24-2010 02:22 AM ET (US) I my try something similar to confirm my structure/down scan is reporting port and starboard correctly. As the installation instructions implied that the transducer cable should be away from the stern, which seemed strange to me. The HDS units has a menu setting to allow the readings to be reversed, so no problem if it is initially set up wrong. Regards Steve