Woody,

I'm not aware of any manufacturers with such a product now and it sounds like you concur it's not currently offered.  My own sonar knowledge isn't good enough to know how substantial the benefits would be of turning down the power in order to try and make out better detail but in my own experiences, I don't believe I've seen cases where there's too much power applied.  

Ben

Digital systems are more apt to lose detail by turning down the power. It reduces the signal to noise ratio. Much like a digital camera works comparatively poorly in lower light. Adequate power is what's important. More power is good. Higher frequency finds smaller objects as the waves are smaller. To produce a 3d visualization, the sonar's transducer needs constant orientation and position information. Otherwise, if the boat moves, it appears to the system that the depths and angles are changing.

You probably can't easily build something. It'd be easier to take a second job and buy a Furuno DFF3D and Nobeltec Professional with the Dff3d software module.

Thank you for your kind replies Ben and Jason. I hope this illustration provides clarity on my perspective: imagine looking on a white floor for a dropped contact lens with a 1M candlepower spotlight (too much light). Really, the best method for illuminating a lost contact lens is to take a small low-power directional light (perhaps even a low-powered laser pointer like they sell at Dollar Tree), and laying it flat on the surface, then sweeping it slowly across the area watching for diffraction or shadows. The intent is not to illuminate the surface, only the invisible contact lens, and that is my intention, to turn down the power so low that the soft sea bed is hardly visible on the screen, but the metallic objects reflect a noticeable marker on the screen, that is my goal. There are a number of products in use today that provide this control, and all of them are generally beyond my budget (hydrography and bathymetry professionals install them in their vessels, e. g. NOAA’s r/v “Bay Hydro II” in Solomons MD, and Okeanos Explorer uses such equipment onboard as well as on launches, here is a link which includes links to pages specifying the exact equipment: https://oceanexplorer.noaa.gov/okeanos/about.html ) however this is not what I want to do today, since my focus is the shallow waters of the Chesapeake Bay, specifically my own berth.

I’ve had an interest in hydrography for several years; this endeavor is merely the manifestation of the dream. Here is what I know thus far:

Higher resolution comes from higher frequencies and also higher scan counts, thus the chirp multibeam capabilities of the latest products (Raymarine Realvision 3D, Humminbird Mega, Garmin ClearVue, to name a few) can produce display images showing your fishing lure passing through the water, or even depict fish tails indicating what direction a fish is pointing (I do not fish, but that is the market for these products). The biggest drawback to high frequencies is the attenuation of the water and the line-of-sight nature of such reflective technologies. For deeper imagery, lower frequencies are used (and higher transmit power, thus there is an advantage to manual power adjustment for shallow and deep water observations).

As for adjustable transducer power, the “Fish Hunter 3D” (a Lowrance product) offers power adjustment and raw data viewing in the iphone app. The app also provides a “bathymetry mapping” function whereby a user can record their own seabed mapping, although the output for this device is low-resolution. There are several low-resolution devices on the market, I am continuing my research...

I guess my intent behind this message is to query others in hopes that someone might have discovered the ability to adjust the power output manually in order to reduce the noise of the reflected signal. I want to refit my vessels with equipment that will enable me to produce charting products (and awaken my inner hydrographer) but that is a long-term goal; today I just want to be able to “see” the crimpers I dropped off the boat. 😊

I wish my fellow boaters long life and warm dry beds.

Woody

I am sorry for the long message.