Topic: image interpretation

[Crispen]

Hello All

I am currently in Banda Aceh, where the large tsunami struck several years ago.  When the wave receded it dragged back with it a huge amount of debris.  So I am seeing a wide range of objects. I am finding the size of objects displayed and the depths a little non-intuitive.  I guess what I am looking for am looking for a good scientific explanation of what I see on the screen; size depth, offset, etc..


Best regards

Crispen

[RGecy]

Crispen,

Side scan interpretation can be difficult sometimes, and other time straight forward.  If you have some snapshots of some of the images you have it would be a good start to getting help.

The first thing you need to do is make sure you are scanning at the right boat speed and settings.  Boat speed, chart speed and range will affect the size and shap of the targets.

Here is some good reading. http://forums.sideimagingsoft.com/index.php?topic=333.0

The 797c also has a smaller screen size and you may want to experiment with playing back recordings on the computer so you can see the images on a larger screen.  Several software programs also offer measuring tools to measure an objects length as well as calculate the height off the bottom.

Many times, the objects shadow will reveal more information than the hard target return.

Take a look at some of the here in the image gallery and general pictures forum.  Many of them have descriptions on what the image is showing.  I will try to post some more info later tonight.

Robert

[IRC Kevin]

Hi Crispen,
I've found recording trips and then playing them back on both the Humminbird and also on my desktop using SiView and Humviewer to be invaluable. SiView has a measurement tool, which has proved very accurate on wrecks where I already knew the vessel and its length.

[Crispen]

Hello Robert, Kevin

Thank you very much for the feedback.  Sorry for the delay in responding out in the islands collecting images, testing different settings.  A lot of the images that I am recording are of coral reefs or objects where I do not know the dimensions, seems it will take a bit of practice.

Thanks again

Crispen


 

[IRC Kevin]

Hi Crispen,
You can download SiView from here  http://www.mnorwood.com/SIView/ The measuring tool is very good and accurate to at least a couple of inches.
regards,
Kevin

[sonar2000]

A point to consider is, when "reviewing" recorded sonar files nothing compares to the Humviewer. While the sonar unit itself has a playback feature the process of reading the screen is a lot more user friendly with humviewer and playback control is more of an exact control. Added to the humviewer is measurment and enlargement of the target.   Humview is worth the effort to learn.  Chuck

[Crispen]

Hello Chuck

You don't have to sell me, I am already sold.  From the screen shots and the function descriptions, it seems like Humviewer the interface is quite well designed and it provides a number of functions that I absolutely require, e.g.  output depths to CSV. 

My problem is that whenever I try to load a file larger than a few seconds, I get a error message "illegal data" associated with two different time stamps within the file.  This error message repeats 4 times and while the first number is consistent, the second number is always slightly less and varies across each of the four errors messages.

I appreciate Martin's efforts and look forward to using the software.

Best regards

Crispen