GGE3353 Lab 2

Lab 2 -- Bottom Detection

Due date October 18th --- E-mail pdf to (In MSword use save as--pdf). Individual submissions.

Questions can be e-mailed to or visit Majed in E16.

  1. Download data and matlab routine from blackboard.
  2. Code up bottom detection, should be at least configurable for threshold, range gate, echo duration
  3. Load data in matlab, create images, and plot a few echo traces to estimate threshold, range gate, and echo duration.
  4. Run bottom detection for 33 kHz and 200 kHz channels
  5. Load in the ascii file and associate the seconds since 1970 with each ping. From lab 1 the Knudsen attitude file has a seconds since 1970 as well as the Newfoundland summer time. This will allow you to use the seconds since 1970 to put a heave and UTC value with each ping (you will do this in lab 3).


  1. Compare/contrast bottom tracking between different frequencies
  2. Explain what the range gate, threshold and echo duration are, and their role in the bottom detection.
  3. In the echo trace, what is the first spike?
  4. Why would this vessel have the two different frequencies?
some tips ...
  1. In the gray scale image, high backscatter (e.g. the seabed) should appear darker, so flip the 8bit values before
    writing the array to an image-file.
  2. For delivrable 1 & 2: Ping # on the x-axis, Sample # on the y-axis. Also you may find the imagesec function in Matlab useful.
  3. For delivrable 3: Time (seconds since 1970) on the x-axis. For example in seconds since the start of line.
    Sample # on the y-axis.

Created by Steve Brucker 2006, last modified October 2nd 2010, Travis Hamilton