SO432, Geographical Information Systems

Exam 1, Fall 2004

Definitions 10@3
Short Answer 2@10
Figures 2@15 and 2@10
Total 100

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

Quality of your answers is important.   For full credit your should use correct terminology, and show that you understand the concepts involved.

Comments are key points often missed, and not complete answers.

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

Answer 2 of the following 3 short answer questions.  Each is worth 10 points.

(a) A NIMA publication lists about 20 ellipsoids used around the world, and over 100 horizontal datums.  What is the difference between an ellipsoid and a datum, and why are there so many more datums than ellipsoids?

(b) Your mother gives you a $1000 GPS with color screen and built in map data base that will only produce output on NAD27.  Could you safely use this GPS on training missions in the United States?  When deployed to Iraq?  Why or why not?  WGS84

(c) Are data standards in GIS data formats good for users, data producers, or software vendors?  Why or why not?



Birch Ave A41


Beach Ave A41


Solomons Island Rd A31


Chesapeake Bay Dr A31


Chesapeake Beach Rd A31


State Highway 32   A25






Birch Ave Local, neighborhood, and rural road, city street, unseparated


Beach Ave Local, neighborhood, and rural road, city street, unseparated


Solomons Island Rd Secondary and connecting road, State and county highways, unseparated


Chesapeake Bay Dr Secondary and connecting road, State and county highways, unseparated


Chesapeake Beach Rd Secondary and connecting road, State and county highways, unseparated


State Highway 32 Primary road without limited access, U.S. and State highways, separated


  Access ramp, the portion of a road that forms a cloverleaf or limited access interchange

Discuss the terminology applied to databases like these.

How does a database like this differ from an ASCII TIGER file?

What is the difference in coding between the two databases?

Which coding do you think is better, and why?

What would it require to make this into a GIS database, and why would someone want to use a GIS database?

Orthographic: not equal area and not conformal
Stereographic: not equal area but conformal.

Not polar stereographic, which would be centered on a pole

Lambert azimuthal: equal area but not conformal

What geometric surface was used for each of these three projections?

What is the name and purpose of the round objects placed on the maps?

How do the characteristics of the three projections differ?

Could any of the maps be equal area?  If so, which one(s), and why?

Which of the three might be used by the military for maps and charts, and why? conformal required

Is this map a Mercator or UTM projection?

How could you tell? Meridians converge. Meridians are the boundary between color coded UTM zones, where the first letters of the 100K grid squares change.

What is the difference between the two projections? Both are cylinders, but oriented 90 degrees to each other.

What is the pattern of distortion on this map projection?  Increases away from the central meridian.

What are the letters on the map, and were they of any help in determining which projection this was? MGRS 100K grid zones.  They show the meridians and that they are converging, which does not happen with the Mercator


(10 points)

What is the difference in the two maps shown above?  Which is better? Defend your answer.

How does the concept of scale apply to the two maps, and how they were digitized?


Scale in vector depends on how close the points are digitized, and how smooth curves you can get.  Scale in raster depends on the DPI.