Author Topic: Extract bottom hardness data?  (Read 3478 times)

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Offline tspier

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Extract bottom hardness data?
« on: August 05, 2013, 07:53:21 PM »
I would like to extract the bottom hardness data from my 998c unit for mapping purposes. Is this possible? If so, what is the best software to use? What units are the hardness values in? Note that all I need is a Lat/Lon point with a hardness value.


Offline TroyBoy30

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Offline tspier

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  • Joined: Aug 2013
  • Location: Macomb, IL
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Re: Extract bottom hardness data?
« Reply #2 on: August 08, 2013, 05:52:04 PM »
Looks nice, but for research purposes I need access to the raw data. Anyone know how to extract it?

Offline matt@reefmaster

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Re: Extract bottom hardness data?
« Reply #3 on: August 09, 2013, 03:27:35 AM »
Hi,

Resolving hardness values from raw sonar data is a non-trivial process - but if you are keen you can give it a shot. You'll need to extract the sonar returns from your HB sonar log files, along with associated depth and position data.

Take a look at this and this for some background on the general principles. There's plenty more to be found on the web, of course.

With regards to units, the best you can hope for is a set of relative hardness values - there are too many variables in the field and equipment. Even generating comparable results from repeated runs across the same area, using the same equipment, can be challenging.

Also note that a "hardness" on its own is not always is not always enough to determine the bottom type  - researchers will usually consider both the first and second sonar returns (E1 and E2), which relate to "roughness" and hardness. For example, hard sand and rock might show similar hardness values, but will show very different roughness values. This presents its own challenges for us as many people do not log the E2 return - although if you are interested in the bottom type you should really make a habit of keeping any E2 returns visible on the screen, as relative hardness is much easier to discern here.

We are currently working on a bottom hardness module for ReefMaster which will offer E1/E2 classification, along with a form of peak sv analysis.

thanks,
Matt

ReefMaster - Waypoint Management and Underwater Mapping Software for Fishermen


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