Why not use sonar in dirt?

[Darp]

Hi,

My first post. I have a hummingbird have not used yet.

But have used refraction seismic machine in dirt/rock. A sledgehammer type is good to 100' or so.

The question is sonar especially SSS is so darn easy to use, you get a picture. Was out on Tahoe a few weeks ago it even picks up the fishing line 50 feet down!

But using seismic is a big pain, it just numbers you have to process and build your on picture with, and do a lot of guessing.

Have noticed that sonar works into the mud to bottom to show bedrock shape below.

Anyone here know why sonar can NOT be used to image thru dirt and gravel to bedrock? Hopefully dry dirt but even wet soil or river bottom would be much easier than seismic machines.

Thanks in advance.

Darp

[Darp]

Tritech SeaKing Parametric Sub Bottom Profiler (SBP)

http://www.tritech.co.uk/products/pr...metric_sbp.htm

Found another post here about Sub Bottom Profiler, which is part of the solution, when water on surface. That link shows some pics.

I have one app which a Sierra river with 2' of water and 12' of gravel, sand, boulders, maybe my Hummingbird could do that. Not sure how it would handle 3' boulders before you get to bottom? They objective would be to see bottom bedrock image.

But again the question persists, fishing sonars are cheap, easy to use and give great detail. Seismic (Refraction and Reflection) are expensive, very hard to use and give poor detail. It would seem possible to use the principal of fishing sonars for shallow dirt gravel imaging. Has anyone here every seen such a use of sonar?

Cheers

[Jim Kennard]

The difference is in the frequency and intensity. If there is very light silt then a 200KHz depth finder or side scan sonar may be able to penetrate the bottom a few inches or so. Sub-bottom profilers work at a much lower frequency of 10KHZ or less. They also produce a much more powerful signal. Sub-bottom profilers vary in size and intensity depending on the amount of penetration and type of sub bottom material needed to penetrate through.

[Darp]

Hi Jim,

Thanks. With std SSS and fish finders that can see thru sediment to bedrock quite well. Lets say in 20' lake with 10' of sediment, are you saying if it is sand or gravel it would not see thru it, only thru mud?

I do understand the power thing. Water is great for sound transfer, rock good and dirt poor. But sonar in water uses tiny power. Seems cranking up the power ten times is doable, and from your post frequency needs to be lowered too. But the prize is so good its worth the extra power. If I could see thru 10' or dirt or gravel would be happy camper.

Another way would be to produce the send signal via sledgehammer as refraction seismic machines do. The signals are cleaned up and amplified by 3 or 4 strikes and overlaying the signals to get rid of noise.

Do you think current SSS technology could be used to receive signals and generate image from transducer, but use outside powerful send signal?

Cheers

[Darp]

Maybe SSS for mud gravel is not the way,more think about. Its great for detail above the bottom, but the subsurface stuff have seen is non SSS sonar.

Still wonder if anyone has tried to put sonar on steroids for use in dirt and gravel?

[Darp]

Study on 1.4 meter seismic imaging

Very little is said about doing it (ground sonar) but found this


GEOPHYSICAL RESEARCH LETTERS, VOL. 37, L07405, 5 PP., 2010
doi:10.1029/2010GL043034
Ultra-shallow seismic imaging of the top of the saturated zone
Ultra-shallow seismic imaging of the top of the saturated zone
Steven D. Sloan
Engineer Research and Development Center, U.S. Army Corps of Engineers, Vicksburg, Mississippi, USA
Georgios P. Tsoflias
Department of Geology, University of Kansas, Lawrence, Kansas, USA
Don W. Steeples
Department of Geology, University of Kansas, Lawrence, Kansas, USA
We collected ultra-shallow seismic-reflection data to image the near-surface stratigraphy of a Kansas River point bar. We were successful in identifying a discontinuous clay layer and the top of the saturated zone at depths of 0.95 and 1.4 m. Seismic walkaway data collected using various .22-caliber ammunition show that decreased source energy is necessary to generate higher frequencies and prevent clipping of critical near-offset traces needed to identify ultra-shallow reflections. The seismic reflections exhibited average normal moveout velocities of 180–195 m/s with dominant frequencies of 200–450 Hz. Coincident subsurface features were also imaged using 200-MHz ground-penetrating radar. This study presents the shallowest seismic reflection from the top of the saturated zone reported in the literature to date and further demonstrates the potential of using seismic-reflection methods for ultra-shallow imaging of the subsurface as a stand-alone tool or in conjunction with other high-resolution geophysical techniques.

[Darp]

What current seismic data looks like + Research paper

http://www.crewes.org/ForOurSponsors...02/2002-56.pdf


The above link is a 2002 survey on shallow seismic technologies.

http://rr-inc.com/Frame%20Pages/Tech...ic/seismic.htm Is an up today review of current methods, which I am familiar with. If you want to understand reflective and refraction seismic imaging this 2 page article has it concise.

From goggling around it appears that no one has even tried to create ground sonar that works like boat sonar systems.

Seems feasible to me.

Cheers

[Rickard]

This forum is obsolete, please go to this forum if you need advice on SSS and Humminbird (and in your case, any fishfinder) fishfinders: http://forums.sideimagingsoft.com/

Regards
Rickard

[Rickard]

Oops! English is not my first language, I didn't mean to say obsolete really, I intended to say something like 'not the best place for finding info on Humminbird sonars', sorry.

Rickard