SO432, Hydrography

Exam 2, Fall 2001

 Definitions 6 @ 5 points 30 Short Answer 4 @ 10 points 40 Essay 1 @ 30 points 30 Total 100

For the definitions and short answers, insure that you use proper terminology and show that you understand the concepts and principles involved.

Insure that you devote sufficient time on the essay.  You should do a good job of synthesizing what we have covered.

For full credit the quality of your answer is critical.

Definitions.  Define 6 of the following 8 terms.  Each is worth 5 points:

·        NAVD 88:

·        Father Point, Quebec:

·        Graticule:

·        Multibeam echosounder:

·        Molodenskiy Transformation

·        Orthometric height:

Short Answer.  Answer all 5 of the short answer questions.

1.  The tidal record above covers last September at Annapolis.  It shows both the actual and predicted tides.   Use the diagram to explain the following:

·        How is the zero point on the vertical axis determined?

·        How can all of the predicted readings be above 0 on the vertical axis, and only one day’s (09/22) observed readings dip below 0?

2.  The two graphs on the next page show an error analysis for a GPS survey of a tidal benchmark.  The top graph shows the 134 readings, their average, and the accepted position of the benchmark.  The accepted position is 9 meters from the average of the 134 readings.  The bottom graph shows the distribution of the differences of the individual readings from the average position.

• Use the two diagrams to explain how we measure error for GPS readings.  You should clearly discuss both CEP and RMS error, and how they would be depicted on each diagram.
• What is the probability that a single GPS reading would be off by 9 m?  Explain how you arrived at this answer.

3a.  What are the large numbers and letters on the map below?  What is the pattern used in assigning the numbers?

3b.  Is 41IJK43567 a valid MGRS position?  Why or why not?

4.  We normally use the TISSOT indicatrix to show map distortion.  Using just the MGRS on these two maps, can you:

• Determine the projection of each map.
• Indicate the pattern of distortion on each map.

Essay.  This diagram shows a screen capture of a GIS.  Use the diagram to:

• Define what a GIS is.
• Discuss the parts of a GIS.
• Discuss the kinds of operations you can perform with a GIS.
• Describe how a digital nautical chart can be considered a GIS, and what aspects of a GIS will be most important for the digital chart.