CVEN 254 Exam 2 Jason Howell

A set of flashcards based on lecture notes about photogrammetry, satellite positioning systems, and GPS concepts.

What is photogrammetry?

Photogrammetry uses ultra high resolution aerial images to produce actionable data for GIS mapping systems.

Raster Data

Digital Elevation Models (each cell represents an elevation), Used in Most Remote Sensing Studies

GIS

computer system capable of capturing, storing, analyzing, and displaying geographically referenced information

GPS

Global Positioning System (GPS) uses trilateration via satellites to determine precise locations on Earth, enabling accurate navigation and tracking.

What type of data do Digital Elevation Models represent?

Digital Elevation Models represent elevation where each cell corresponds to a specific elevation value.

What does GIS stand for?

GIS stands for Geographic Information System, a computer system for capturing, storing, analyzing, and displaying geographically referenced information.

How does GPS determine the coordinates of positions?

GPS employs trilateration to calculate the coordinates of positions at or near the Earth's surface.

Which satellite positioning system is used in Europe?

The Galileo system is used in Europe for global satellite navigation.

What is the function of the fourth satellite in GPS positioning?

The fourth satellite corrects timing errors in the GPS receiver's clock.

Describe why 4 satellites are needed to obtain an accurate GPS position.

A GPS receiver needs four satellites to accurately determine its position. The

first three satellites help calculate the location using trilateration, while the

fourth corrects timing errors in the receiver’s clock. Without the fourth

satellite, the location data would be unreliable

What is the difference between an open and closed traverse? What are the angles that you turn

in each? Draw a diagram to illustrate each type of traverse and show the angles that you turn in each.

An open traverse does not return to its starting point, making it useful for road or

pipeline surveys. A closed traverse forms a loop or connects to a known point,

allowing error checks for accuracy. In an open traverse, angles are measured between

successive points, while in a closed traverse, interior or exterior angles are used to

ensure closure.

What is the difference between an open traverse and a closed traverse?

An open traverse does not return to its starting point, while a closed traverse forms a loop or connects to a known point.

What is a back azimuth?

A back azimuth is found by adding or subtracting 180° from the given azimuth.If the

azimuth is less than 180°

, add 180°; if it's greater than 180°

, subtract 180°

How does LiDAR distinguish between ground and vegetation?

LiDAR distinguishes surfaces by analyzing how laser pulses reflect off different objects, with unique patterns for vegetation and water.

What is magnetic declination?

Magnetic declination is the horizontal angle between magnetic north and geographic north.

What are the three segments of a satellite system?

The three segments are space, control, and user; with space including satellites, control involving ground stations, and user being GPS devices.

Explain differential correction in GPS.

Differential correction improves GPS accuracy by using a reference station to identify signal errors and transmit corrections to receivers.

What is an azimuth?

An azimuth is the direction of a line as given by an angle measured clockwise from the north end of the meridian.

What is a bearing?

A bearing is the direction of a line measured counterclockwise by the acute angle between the line and a meridian.

GNSS

Global Navigation Satellite System (GNSS) is a general term for satellite navigation systems that provide geospatial positioning with global coverage.

Base Map

reference layer that provides context, such as roads, water features, and boundary lines, for overlaying additional thematic information in GIS.(outline of basic features)

What is Remote Sensing?

Geospatial data collection and interpretive analyses for both airborne and satellite Imagery

Nadir Angle

angle between an observer's line of sight and the point directly beneath them (the nadir)

Zenith Angle

angle between an observer’s line of sight and the point directly overhead (zenith)

Lidar

uses laser targeted distance measurement to create a detailed point by point map of objects

position in space

Radar

radio detection and ranging, a system that uses reflected radio waves to determine the

velocity and location of objects

Name at least one satellite positioning system that is not GPS (the USA system). Name

the system from Europe, Japan, China, etc.

Europe has the Galileo system, which provides global satellite navigation. Japan

operates the Quasi-Zenith Satellite System (QZSS) to enhance GPS accuracy in the

region. China’s BeiDou Navigation Satellite System (BDS) serves as an independent

global positioning system

Problem: Convert the following azimuths to bearings

20°08ˊ

280°16ˊ

= N 20°08ˊ E

= N 79°44ˊ W

Convert the following bearings to azimuths

N 10°21ˊ W = 349°39

S 60°44ˊ E = 119°16ˊ

Name and describe 2 sources of satellite/GPS error discussed in class.

Path error and Clock error

Explain the difference between magnetic north and geographic north

Geographic north, or true north, is the fixed point where the Earth's axis meets the North

Pole. Magnetic north is where a compass needle points, shifting over time due to changes in

Earth's magnetic field. The difference between them, called magnetic declination, varies by

location and must be accounted for in navigation.

Explain differential correction used by GPS satellites.

Differential correction improves GPS accuracy by using a reference station with a known

location to identify signal errors. The station calculates corrections and transmits them to GPS

receivers, allowing for more precise positioning. This method helps reduce errors caused by

atmospheric delays and other signal disruptions.

What is a back bearing ?

reverses the direction of a bearing by swapping "N/S" and "E/W.

" For

example, N 30° E becomes S 30° W