Chapter 3

Question 1

coordinate pairs

coordinate space

Answer 1

specifies the location and shape of a particular feature

is an agreed-upon range of coordinates used to portray the features

Question 2

origin

map units

Answer 2

the point of coordinates marked 0,0
-origin of the coordinate system

the surveyor uses meters to record the distances and determine the coordinates, therby establishing meters as the map units

Question 3

Geographic Coordinate System(GCS)

Datum

Answer 3

System of measurment using degrees as units and longitude and latitude

datum: different approximations have been developed to meet specific mapping needs, each one representing a slightly different shape for the earth

Question 4

earth’s shape is a _____, an oblong sphere with a major and aminor axis

Answer 4

spheroid/ellipsoid

Question 5

the closest approximation to earths shape is the _____

Answer 5

geoid

-based on gravity and sea level

Question 6

A datum that finds the best fit overall is called an ____-______ datum

A datum of best fit for a particular region is called a ____ datum

Answer 6

earth centrered
-World Geodetic Survey of 1984 is an earth centered datum based on the WGS 1984 annd is commonly used for international data sets and web maps, default for most GPS’s.

local
ex: NAD83

Question 7

transformation

projection

Answer 7

at times it is necessary to convert from one datum to another

converting locations on a globe to locations on a piece of paper

Question 8

projections are grouped into three major classes

Answer 8

1. cylindrical
   - lies tangent to(touches) the earth at the equator along a great circle
   - transverse projection is when you rotate the cylinder sideways and make it tangent to the earth along a line of longitude
   - preserve shape or direction at the expense of area and distance
2. Oblique
   - places the tangent line at an angle
   - distortion increases away from tangent line
3. Conic
   - is based on setting a cone on the sphere
   - if the cone is tangent to the globe along a line of altitude, then the projection is tangent
   - line of tangency is called standard parallel
   - you can also place the cone through the sphere so that it touches in two places-a secant projection
   - polar projections are also part of this
   - preserve area or distance at the expense of direction and shape

Question 9

four properties of map features may be distorted:

Answer 9

area, distance, shape, and direction

Question 10

T OR F

Rasters have coordinate systems and projections just as vector feature classes do.

Answer 10

T

-rasters can be projected from one coordinate system to another, although the algorithms are more complicated

Question 11

_____(1st order) transformation can translate, rotate, and skew the image to match the points

Answer 11

affine

2nd order: shape is messed with

3rd order: shape and parallelism messed with

Question 12

rubbersheeting

Answer 12

in second or third order transformation allows the image to stretch or contract locally for a better fit

Question 13

Root Mean Square error

Answer 13

used to measure the difference in distance between ground control points

Question 14

UTM

Answer 14

• 6 DEGREE intervals, producing 60 zones around the world
• false northing= 10 million meters
• false easting=500,000 meters

Question 15

Project tool

Answer 15

outside data from different coordinate systems are always converted to the official one at the outset

Question 16

T OR F

THE x and y values are always correct?

Answer 16

T