SonarTRX Blog

Blog for www.sonartrx.com

SonarTRX 12.1 Beam Angle Correction

clock July 12, 2012 01:20 by author SonarTRX

SonarTRX 12.1 has a new Beam Angle Correction feature (BAC) useful for ballancing out the brightness and contrast of the slant range corrected images. To illustrate some of SonarTRX's basic image correction and BAC, here are some images recorded from a kayak, in an area of water depth 15 feet The track-distance of each image is about 200'.

Example 1: Images that includes the water column (i.e. No Slant Range Correction)

The image to the left is based on the original uncorrected data from the Humminbird recording and has a slightly lower contrast. The image to the right has been corrected to maximize contrast, but no adjustment has been made for the weaker signal from large beam angles.

Standard images with water column - with or without basic correction.

 

Example 2: Slant Range Corrected (SRC) images.

The image to the left is corrected to maximize contrast. There is a large drop in brightness at higher beam angles. The image to the right has undergone Beam Angle Correction to even out the brightness and bring out additional details at far ranges. (A high contrast setting was selected to bring out as much detail as possible from the far ranges.)

Slant range corrected images - without and with Beam Angle Correction.

 

Close-up of example target on the seabed

The images below are close-up details of one of the targets in the corresponding SRC image above. The image to the left has a lower contrast and a slight drop in brightness from top to bottom. The image to the right (w/BAC) has a higher contrast and more even brightness top-to bottom of the image.

Closeup of Targets from SRC images - without and with BAC.

 

 

 



Position errors of marked targets due to heading differences

clock May 15, 2012 21:45 by author SonarTRX

When marking targets visible on sidescan data from the Humminbird/Lowrance sonars, it is important to keep in mind that the boat heading (and normally the transducer heading) is not necessarily the same as the "Course Made Good" (CMG) based on GPS positions.

If the boat is pointing into the wind or strong current in order to stay on track, and the marked targets are far away from the track, this error may be large. The image below illustrates this:

Angle Errors

  • The boat (and the transducer) is pointing to starboard by 20 degrees relative to CMG.
  • The Brown image is calculated based on the assumption that the transducer is aligned with CMG.
  • The Blue images are based on a "pointing angle" of 20 degrees (i.e. you point the vessel 20 degrees into the wind/current in order to stay on track of the survey line)

In essence: When marking a target, keep in mind the heading of the boat relative to CMG and remember that the position of the targets may need to be adjusted for this heading error. If making the marks on the sonar during the survey, it is important to also make a mark at the track-line, since that is the "point of rotation" for this correction. The extent of the search area can then be increased to account for uncertainties in the transducer-angle.

If the boat is drifting while recording, the difference between CMG and the heading of the boat may be very large, and even completely flipped 180 degrees (...drifting backwards). In that case, if you targets are marked at a certain range, the marks may even be interpreted as being on the WRONG side, since there is no available information about the actual heading of the transducer. (i.e. everything is based on the CMG from the GPS)

The SonarTRX images can be corrected for a constant heading differences for a given batch of image-tiles. This is done from the Mosaic creation dialog.



SonarTRX Blog

clock May 2, 2012 09:39 by author SonarTRX

This is the blog for SonarTRX. Please visit the main web-site for product information:

www.sonartrx.com



SonarTRX 10.14 release

clock March 17, 2012 08:21 by author SonarTRX

The 10.14 release of all 3 product-versions is now available for download.

For product information and release notes for new and older versions, please visit the main web-site:

www.sonartrx.com



SonarTRX 10.13 has been released

clock February 10, 2012 03:47 by author SonarTRX

The 10.13 release of all 3 product-versions is now available for download.

For product information and release notes for new and older versions, please visit the main web-site:

www.sonartrx.com



SonarTRX v10.13 Beta

clock January 26, 2012 10:52 by author SonarTRX

SonarTRX 10.13 Beta is now available for download.

For product information and release notes for new and older versions, please visit the main web-site:

www.sonartrx.com



Support for DeepView files (*.dvs)

clock December 31, 2011 04:40 by author SonarTRX

An updated version of SonarTRX 10.12 is now available with support for DeepEye 340 sonarfiles by DeepView (*.dvs)

For product information and release notes for new and older versions, please visit the main web-site:

www.sonartrx.com



SonarTRX v10.12 released

clock December 23, 2011 01:45 by author SonarTRX

Version 10.12 of all 3 products has been released.

For product information and release notes for new and older versions, please visit the main web-site:

www.sonartrx.com



New product: SonarTRX-LSS has just been released

clock November 13, 2011 03:34 by author SonarTRX

The new version of SonarTRX, dedicated to Lowrance sonars has just been made available online. SonarTRX-LSS v10.11 supports both *.sl2 and *.slg sonar recordings.

For product information and release notes for new and older versions, please visit the main web-site:

www.sonartrx.com



Coming soon: SonarTRX-LSS, for Lowrance StructureScan sonars

clock November 7, 2011 22:09 by author SonarTRX

In the works is a new version of SonarTRX that suports Lowrance *.sl2 files. The new product will be called "SonarTRX-LSS", and will be priced similar to the corresponding product for Humminbird sonars (SonarTRX-SI)



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Please visit the main web site for more information:

www.sonartrx.com

 

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