SO432, Hydrography

#### Exam 1

Fall 1999

Definitions    10 @  3        30   ___________

Short answer    5 @  6        30   ___________

Short answer    1 @ 10        10   ___________

### Essay           1 @ 30        30   ___________

Total                        100   ___________

Read the directions carefully.  You have a selection of questions for the definitions and the short answers.

Insure that you devote at least 10 solid minutes on the essay.

Part of a JOG-A in CADRG format.

Definitions:  define 10 of the 12 terms with a concise sentence that clearly shows your understanding of the term:  Each is worth three points.

(a)    Portolan chart:

(b)   Selective availability:

(d)   WGS84:

(e)    Grid data:

(f)     NIMA

(g)    GI&S

(h)    Tissot indicatrix:

(i)      DPI:

(j)     Lossy compression:

(k)   Molodenskiy Transformation

(l)      Graticule

Answer 5 of the 6 short answer questions ; each is worth 6 points.

(1) You are surveying points for a new chart.  Which is better: a CEP of 50 m, or a 2DRMS of 75 m?  Explain what each term means and defend your answer.

(2) Differentiate radiometric and geometric corrections for side scan sonar, and give a reason why each type of correction might be required.

(3) You have the following two MGRS grid coordinates, which are accurate.  (The only difference is the second digit.)

# 12SNV0000083947

(a)    Explain what each grouping of letters or numbers represents.

(b)   Could these two coordinates be close to each other?  Explain why or why not.

(4) What is a datum, and why is it important?

(5) Discuss the difference in the geometric properties between the Mercator and transverse Mercator projections.

(6) Discuss whether a globe would make a good map, and whether the problem this poses is worse for large scale or small scale maps.

You must answer this question; it is worth 10 points.

The following equations all pertain to the same map projection.

x := a * (l-lo)

y := 0.5 * a * ln( (1 + Sin(f)) / (1 - sin(f)) * [(1 - e * Sin(f)) / (1 + e * Sin(f))]e)

f :=  [p/2] - 2 * ArcTan([exp(-y / a)] * [(1 - e * sin(f)) / (1 + e * sin(f))]0.5 * e))

(Note that this equation requires recursion or iteration, since f is on both sides of the equation and cannot be isolated)

l:=  lo + x / a

h := sqrt[1 - e2 * Sin(f)2] / Cos(f)

k := h

(a)    Explain the purpose of each of the six equations.  You may group the equations if this makes sense in terms of their purpose.

(b)   Is this a spherical or ellipsoid projection?  How could you tell?

(c)    Is this a conformal projection?  What does this mean and how you could tell?

(d)   Which of the major projections used by the military could these equations represent?  How could you tell? (Do not waste much time here if you do not know the answer.)

Essay.  This is worth 30 points.

NIMA has a new director, who has requested a briefing on a proposal to develop a new Mapping & Charting Digital Unified Database (McDUD).  As is typical for many military assignments, the new two star is a war fighter with no previous assignments in mapping or charting.  You must prepare a short briefing that addresses and explains the following points:

·        What is the difference between a map and a chart?

·        What kind of a data structure would you use to provide maps and charts well into the 21st century?

·        Could a single digital data base meet the demands of all four services and replace the current paper topographic maps, hydrographic charts, and aeronautical charts?   Why or why not?