We have two data sets, which are only available locally. They will
download when you start the lab if they are not already on the computer, and will take a while because the data sets are
- Sidescan survey done over 5 days. The sidescan data for this survey requires 135 GB
of storage, and we will work with just a small portion of it.
- Database showing all 79 lines. Each
line was originally a single file about 2 GB in
- Three segments of the sidescan data (200 MB+
each, about 10% of each line). These cover the best targets
observed on the survey.
- Aeromag survey done over 2 days.
- Shapefiles with survey lines from two
missions, which show the
path flown by the aircraft on two successive
- Mission LH261 flew 1853 km
or 1000 nautical miles
- Mission LH271 flew 1317 km
or 711 nautical miles
- Database of the 89 targets identified by the
crew in the aircraft, and then later with post
processing of the data which added graphics of
- Database with the 240,000 track and magnetic
- There is a TIME field; you
will have to figure out what the units are.
LH261 goes from
36900 to 54400,
a range of about
LH271 goes from
33500 to 46000,
a range of about
- There is true air speed in
knots (TAS), so you can
compute how many actual flight
hours were involved.
- Insure that you look at the short wavelength anomalies, as
the measured values mostly show how the earth's
field varies with latitude.
Prepare a report on the efficiency of the two survey methods.
- Compare time required, total length of survey lines, line spacing,
survey speed, and area covered for the two
surveys. Discuss any caveats about your numbers.
- What coverage did the side scan achieve?
- Find the three largest anomalies in the magnetic data.
- Do a crossover analysis for one of the largest aeromag anomalies.
- Show what you think is the best target in the sidescan data, and provide
its coordinates, and what
features you see on the bottom.
Compare the survey efficiency of the two methods
Area computation Compute the area covered by each survey.
You do not want to include turns at the ends of the survey lines
Compute the line spacing for each survey. Insure you have
zoomed in; the accuracy of your measurement is not better than
the pixel size of the map.
- Survey line length
- If the file has a single track line, you can click on the
record, Calculate, Calculate line length.
- If the file has a number of individual tracks, you can add
the line length to each (Edit, Geometry, Line length, and then
get a sum of all the records)
- Sidescan coverage. This is given as a percentage, 100%
meaning every point on the bottom was imaged once, and 200%
meaning every point was imaged twice. It will be equal to
the range/track spacing.
You can get sidescan survey speed from the record information
in the database. Because this area has very large tides, you want to
verify if the speed varies depending on the direction.
Map anomalies Find the three largest
anomalies in the aeromag data using the raw data, insuring that you look at
- Did the survey team identify them and include them in their
- By happenstance, there is a cross line near the largest
- Do a 3D plot of that area.
- Do a Crossover analysis
on two of the crossover points. What is the difference
between the two surveys at this point, and how does it compare
in magnitude with the anomalies.
- Did the survey team identify any targets within the side
scan sonar survey? Can you add any additional targets
which we could look for in the sonar data? (you want a very
narrow anomaly, since a shipwreck will have a very limited
- You can set the size of the grid overlaid on the imagery, to
get a sense of the scale of the features you see.
- What are the most prominent features you see in the imagery?
What is their size scale, and what do you think controls their
- Can you see any likely targets?
last revision 2/6/2016