I conducted a test comparing the actual depth with the depth measured by the Ping2. In the Ping2 software (Ping Viewer), the measured depth was 0.67m, but the actual measured depth was 0.6m. This suggests an error of 7cm. I am wondering if this is a product issue or if the bottom surface of the Ping2 is designed to be used at a depth of 7cm from the water surface.
If it is not a product issue, could you please let me know how deep the product should be submerged in order to be used properly? Thank you.
There’s a 0.3 minimum range the device is capable of detecting (due to ringing vibrations from the pulse transmissions), but you’re past that, and it shouldn’t cause a distance estimate offset.
As I understand it the distance estimates are from the transducer location, which is roughly at the face of the sonar. The main ideas I can think of around measurement error here are
there are objects within the sonar beam that are closer than the point you were measuring to visually
the surface you are measuring has a gradual density change, or the sonar return signal is saturated, so the visual edge of the surface does not align with the results from the sonar’s density estimation algorithm
this may be visible in the profile data
there is some potentially relevant discussion in this thread
In addition to the content of your response, I’m also curious about how many centimeters deep the Ping2’s transducer should be submerged from the surface when measuring the distance from the surface to the bottom. If you have any other cases where the distance from the surface to the bottom was measured, I would appreciate it if you could share them. Thank you.
Hi @mrpk -
It all depends on how the Ping is being moved through the water! If it is perfectly flat-calm water, and the Ping isn’t moving, you can get away with only the face of the transducer immersed underwater. However, the deeper the unit is, the more tolerant of speed through the water and the resulting turbulence and bubbles the measurements will be - you want to avoid interference obviously!
The BlueBoat mounts the unit at a depth of about 12 cm, and only has issues with interference in some cases when performing pivot turns, where bubbles may get thrown in front of the transducer.
Thank you for your response. However, I still have a few questions.
To explain with an example, the actual depth is 0.95m. If the distance from the water surface to the bottom of the Ping2 transducer is 0.07m, then the data from Ping Viewer should show 0.88m. However, in my tests, it shows 0.95m. I’m wondering if this 7-8cm offset is intentional, or if there might be an issue with my product.
PS: The test was conducted in a swimming pool with a flat, solid metal plate at the bottom. I also took measurements at different depths under the same conditions, and the results were consistent
Hi @mrpk -
With such a high-strength reflection environment, I would guess you’re measuring the overall water column depth even though the transducer isn’t necessarily pointed across its entire height. This shouldn’t happen in open water / deeper depths! There is no intentional offset…
If you slowly lower the sonar, at some point it should stop reading the whole water column depth and start measuring the actual separation from the bottom, assuming that happens before the minimum range is reached.
Generally, sonars like this are not going to perform well in tanks or pools!
You may also want to adjust the speed of sound you’re using for the water you’re in, this can help with accuracy!
