quiz 2

Question 1

what are the two types of coordinate systems

Answer 1

• Cartesian coordinate system
• Polar coordinate system

Question 2

what is a map projection and what are the two elements of map projections

Answer 2

Project a round globe onto a flat surface
1.) projective surface
2.)perspective point

Question 3

what are the three map projection surfaces

Answer 3

1.)Cylindrical
2.)Conical
3.)Planar

Question 4

What are the three map projection viewpoints

Answer 4

Gnomonic – Earth center
Stereographic – Earth Surface
Orthographic – infinity

Question 5

where is the view point on a gnomonic viewpoint

Answer 5

Earth center

Question 6

where is the view point on a Stereographic viewpoint

Answer 6

Earth Surface

Question 7

where is the view point on a Orthographic viewpoint

Answer 7

infinity

Question 8

What are the four properties of map projection and how many can be kept

Answer 8

you can only keep 2 and the four properties are
– Area (equal-area or equivalent)
– Shape (conformal or orthomorphic)
– Distance (equidistant)
– Direction (azimuthal or zenithal)

Question 9

What is preserved and not in a cylindrical projections

Answer 9

Shapes are preserved
But not area or bearings or distances

Question 10

what type of projection is mercator

Answer 10

cylindrical

Question 11

what are conic projections best for

Answer 11

Best for hemispheres
or small regions

Question 12

what type of projection is lamber

Answer 12

conic

Question 13

what distortions does conic projection have and what does it keep

Answer 13

Distortions
–Distance?
* Yes
–Areas?
* No
–Bearings?
* Yes

Question 14

what are planar projections good for

Answer 14

Good for one hemisphere

Question 15

what are the types of planar projections?

Answer 15

• Gnomonic projection
• Stereographic projection
• Orthographic projection

Question 16

what are the distortions and what is kept on a planar projection

Answer 16

• Distortions
  –Distance?
• Yes
  –Areas?
• Yes
  –Bearings?
• No

Question 17

what are the pros and cons of UTM

Answer 17

• Advantage
  – Minimal Distortion
• Disadvantage
  – Multiple zones

Question 18

what is a datum

Answer 18

Datum - formal description of the Earth surface

Question 19

what is a geodetic datum and what are its two parts

Answer 19

• Geodetic datum - reference system describing
  Earth’s surface.
• Geodetic datum contains two parts:
  – Shape of the Earth: ellipsoid (geoid)
  – Reference points and axis against which
  measurements are made

Question 20

what is nad 83

Answer 20

• North America Datum - NAD 83
  – Replaces NAD 27 datum
• Initial point in Kansas: Meades Ranch Station
  – Based on ellipsoid
  – Geocentric
  – Suited for the entire planet

Question 21

what is WGS 84

Answer 21

• World Geodetic System 84 - WGS 84
  – Standard use in cartography, geodesy, and GPS
  – Based on the same ellipsoid as NAD83 (GRS80)
  – Coordinate system origin: Earth’s center of mass

Question 22

What are the segments of GPS

Answer 22

1.)control
2.)Space
3.)User

Question 23

How many satellites do we need for GPS

Answer 23

four for trilateration

Question 24

what are the 5 GPS errors

Answer 24

• The errors experienced by the GPS users:
  1. Satellite clock-they are not perfect
  2. Satellite orbit-
  3. Atmospheric delays
  4. Multipath-Signal delay due to scattering off objects on earth
  5. Receiver clock

Question 25

What is a PDOP?

Answer 25

Position Dilution of Precision- basically the further spread out satellites are the better your location will be

Question 26

How can we improve the accuracy of our GPS measurements? 3 ways

Answer 26

1. Solution wait for better acquisition (not very practicable) 2. Solution: Differential GPS (DGPS) Post processing of location using GPS 3.)Real Time Kinematics GPS:Measure the phase of the signal's carrier wave in addition to other information

Question 27

what are the pros of aerial photography

Answer 27

Advantages – Improved vantage point – Capability to stop action – Permanent recording – Broader spectral sensitivity – Increased spatial resolution – Increased geometric fidelity

Question 28

what is focus and what does it depend on

Answer 28

* The process of adjusting the lens to achieve maximum sharpness to the chosen subject * Focus depends on: 1. Focal length of the lens, f distance from lens at which parallel light rays are focused to a point 2. Distance between lens and object, o 3. Distance between lens and image plane, i

Question 29

what is f-stop

Answer 29

f-stop - diameter of the lens opening of a camera f-stop number increases = diameter of the lens opening decreases→ image exposure decreases

Question 30

what are the advantages of digital images

Answer 30

Enhanced image capture capabilities – sensitivity (response to reduce amount of radiation) – linearity (response to amount of radiation) – dynamic range (difference between darkest & lightest) * Reduced time and complexity of creating primary products * Intrinsic compatibility with digital technologies

Question 31

why can we not measure an oblique photo

Answer 31

because stuff in the foreground middleground and background are all different sizes and distances away because of the angle at which the photo is taken.

Question 32

what are the types of aerial photography and do all images have tilt>?

Answer 32

* Type of aerial photos – Vertical – Oblique * All images are tilted, even the vertical ones

Question 33

what is the nadir line

Answer 33

Nadir line - line on the ground directly beneath the aircraft during photo acquisition

Question 34

what is the zenith line

Answer 34

zenith is the line that points up from the earths sufrace while nadir points down

Question 35

what is Stereopsis

Answer 35

* Stereopsis - the perception of depth and 3D obtained from visual information of two eyes * Forward Overlapping with more than 50% essential for stereoscopic coverage-usually 60% * Air base – ground distance between centers of two successive photo * Side overlap of ≈30%

Question 36

what is a photoscale

Answer 36

Photograph scale: one unit of distance on the photo represents a specific number of units in reality

Question 37

what are the two types of displacement

Answer 37

1. Tilt displacement * Caused by a tilt of the image 2. Terrain displacement * Caused by terrain morphology

Question 38

what is tilt displacement

Answer 38

Tilt displacement - the shift in an object's image position on a tilted photo from its position on a vertical photo.

Question 39

what is relief displacement

Answer 39

Relief displacement - the shift in an object's image position caused by its elevation above datum.