Midterm Sample Questions

1) Describe the external data model, the conceptual data model, the logical data model, and the internal data model, as a hierarchy for understanding

data models in GIS.

2) Contrast a linear search with a binary search. To perform the binary search the data must be __ordered________________________.

3) What is an indexed file?

4) In which raster data structures can data compaction be accomplished? Which can not and why?

5) Show how you would use the relation data model to link attribute information to spatial information in a raster environment. Use a table with a

unique ID.

6) Overlay these two data sets to produce a new Morton sequence with all combinations or white (w), black (b), green (g), and red(r) cover types.

Layer 1
00 00 00, w;
01 00 00, w; 01 01 00,w; 01 10 00, b; 01 11 00 w
10 00 00 b;
11 00 00,w; 11 00 01,b;11 00 10,w; 11 00 11,w; 11 01 00, b; 11 10 00, w; 11 11 00 w.

Layer 2
00 00 00, g; 00 01 00, r; 00 10 00, r; 00 11 00 g
01 00 00, r
10 00 00,g
11 00 00,r; 11 01 00 g; 11 10 00 r; 11 11 00 r

7) Describe a problem that is best be solved with a raster data structure and another that is best solved with a vector data structure.

8) Why is the arc/node data structure a superior data structure than the point dictionary for representing geographic data?

9) List and describe the five steps in Cartographic Modeling.

10) A fuzzy tolerance of .002 inches results in how much error from digitization of a 1:120,000 scale map?

11) What is a coordinate transformation and how is it used in GIS?

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