Midterm 1

Question 1

GIS stands for?

Answer 1

Geographic information systems

Question 2

The 2 attributes of GIS

Answer 2

Where: absolute & relative locations of features
What: properties & attributes of those features

Question 3

What is GISci?

Answer 3

How we conceptualize geography and how we collect, represent, analyze, and use geographic concepts

Question 4

What are GIS?

Answer 4

Computer-based systems designed to work with spatial data and info

Question 5

Vector vs. raster data models?

Answer 5

Vector:

• points, lines, polygons
• discrete

Raster:

• grid cells
• continuous

Question 6

What is spatial analysis (& 3 steps)?

Answer 6

• Process of solving problems by:
  1. Modeling spatial data
  2. Deriving results
  3. Examining & interpreting results

Question 7

What is a coordinate system?

Answer 7

A set of numbers that give object position in space

Question 8

What is geodesy?

Answer 8

Science of measuring Earth’s:

• shape
• orientation
• gravitational field
• changes in properties over time

Question 9

What is a geoid?

Answer 9

Our best estimate of Earth’s shape; a model of the global mean sea level

Question 10

T/F: no single ellipsoid can best fit all regions

Answer 10

True

We use a “regionally best fit” ellipsoid depending on starting country

Question 11

What are geodetic datums?

Answer 11

A reference system consisting of:

• ellipsoid with spherical or 3D cartesian coord. system
• set of points/lines that have been carefully surveyed physically to identify exact coord.

Question 12

Geodetic datums are the basis of __________?

Answer 12

Geographic latitude and longitude systems

• Local/geocentric
• Horizontal/vertical

Question 13

What is a (geodetic) datum adjustment?

Answer 13

Using different coord. values to represent a location in space

Question 14

What is a (geodetic) datum shift?

Answer 14

Differences in coord. values when using updated datum

Question 15

What is a geographic datum transformation?

Answer 15

Converting coord. from one datum to another

Question 16

What is longitude?

Answer 16

Angular distance from prime meridian (0 deg)

• East/positive
• West/negative
• 180 to -180 deg
• Parallel to equator

Question 17

What is latitude?

Answer 17

Angular distance from equator to relevant longitude

• North/positive
• South/negative
• 90 to -90 deg

Question 18

What are the 3 types of heights?

Answer 18

1. Ellipsoidal Height (h) - Height above reference ellipsoid
2. Orthometric Height (H) - Height above geoidal surface
3. Geoidal Height (N) - Difference between geoidal and ellipsoidal heights

Question 19

What are map projections?

Answer 19

Transformations of coordinate locations from Earth’s curved surface onto flat maps

Question 20

What are complications in defining coordinates on Earth’s surface?

Answer 20

1. Geography is best understand using Cartesian coord. systems
2. The irregular shape of Earth
3. Measurements are rarely perfect

Question 21

Differences in density of Earth (due to geoid shape) causes ___________?

Answer 21

Variation in gravitational strength; dips and bulges

Question 22

What is dynamic height?

Answer 22

Measure change in gravitational pull from given equipotential surface
- Points at the same dynamic heights often have different orthometric heights

Question 23

What is the great circle distance?

Answer 23

Distance measured on ellipsoid and in plane through Earth’s center
- Intersects 2 points on Earth’s surface and splits spheroid into 2 equal halves

Question 24

What is developable surface?

Answer 24

Geometric shape onto which Earth surface locations are projected

• Conic
• Cylindrical
• Azimuthal