Midterm 1 Flashcards
What is geospatial data
geospatial data is any data with an associated location
What does the term GIS mean
Geographic information system. GIS is computer based mapping and analysis
What is GPS(global positioning system)
Acquisition of real time location information from satellites
What is remote sensing
Acquisition of data and imagery from use of satellites
What are the three basic systems that make up geospatial technology
GIS, Remote sensing, and GPS.
What makes geospatial data unique?
GIS is used in a wide variety of fields, such as homeland security, forestry, city planning.
Describe why geospatial technologies can be considered “geography in action.
GIS technologies can be considered geography in action because you are using basic geography concepts but through technology.
Describe how the discipline of geography is fundamental to understanding geospatial technology
the discipline of geography deals with where things are and why they are where they are. this is fundamental to understanding GIS because GIS deals with spatial thinking constantly.
Tweets sent by Twitter users can be mapped using __________.
geotagging
Some online subscription services like Amazon Prime limit what movies can be streamed and downloaded when the user is outside the United States. What information is used to determine where the user’s computer is located?
IP address
Which job field uses geospatial technology for national security and defense applications?
geospatial intelligence
What projections does the SPCS use? Select all that apply.
-Azimuthal Equidistant projection
-Lambert Conformal Conic projection
-Mercator projection
-Transverse Mercator projection
Lambert Conformal Conic projection, and Transverse Mercator projection
A datum represents __________.
a reference surface used in computing coordinates
What marks the difference between north and south latitude?
equator
The SPCS is used only for data from the __________.
United States
The shortest distance between two points on a sphere is the __________ distance.
great circle
How are negative values avoided in the UTM system when locating features south of the Equator?
by measuring from a false northing
Which of these is equal to 2.5 decimal degrees of latitude?
-2 degrees, 5 minutes, 0 seconds of latitude
-2 degrees, 30 minutes, 0 seconds of latitude
-2 minutes, 5 seconds of latitude
-250 minutes, 0 seconds of latitude
2 degrees, 30 minutes, 0 seconds of latitude
What is a datum
a reference surface or model that is used for plotting locations anywhere on the actual surface of earth. The datum represents the size and shape of earth.
What is an ellipsoid
model of earths shape, larger at the center than the poles.
what is a geoid
places earths surface at mean sea level to account for the pole differences
What is the difficulty of datums
they are a reference point and there are 100’s of them. some are global and some local.
What is a datum transformation
The process of changing measurements from one datum to another.
what is the prime meridian
The line of longitude that runs through greenwhich england and servers as the - degree line of longitude from which to base measurements servers as the starting point of 0.
which direction are negative values in the GCS coordinate system
negative values are used to indicate W or S
Describe how datums and the geographic coordinate system of latitude and longitude are used to reference locations on the Earth’s 3D surface
Geographic coordinate system(GCS) is a global reference system which uses lines of lat and long to find exact positions. The equator serves as the starting point with points running north to south, and the prime meridian serves as the starting point of 0 running east to west. GCS measurements are made in degrees minutes and seconds and can locate any point.
Explain the difference between measurements made on a 3D world vs those made on a 2D flat surface
The difference between measurements made in 3D and 2D is that measurements in 3D are those in the real world. Measurements in 2D are those made on projections. Projection measurements are different because they are translating our real 3D world to a 2D world.
Describe how spatial data are projected onto a 2D flat developable surface of a cylinder, cone or flat plane.
The process of projecting a map involves the use of a developable surface or a flat area on which the locations from earth can be placed. The three main developable surfaces are cylinder, cone, or a flat surface. The place where earth surface touches is the point of tangency and where the map is least distorted
Explain the tranverse mercator projection
This is a cylindrical projection. its used for north to south areas. it becomes more distorted the further away you move form the equator
Lambert conformal conical
This is a conical projection used for east to west tending areas.it becomes more distorted the further away you move from its lines of tangency.
what is Universal tranverse mercator(UTM) and how do you find a point using it
UTM is a grid system that locates coordinates and it works by translating real world locations to a 2d surface. it does not cover the polar regions.
steps
1.)UTM has 60 sections each 6 degrees wide, first find what section you are in.
2.)UTM uses meters with X and Y coordinates. These coordinates are either easting or northing. For north locations count the meters. For south locations negatives can not be used, so count the meters as negative then add 10,000,000 meters this is called false northing
3.)Then measure the points of easting. UTM has no meridian and uses a base point at 500,000 meters. to the east you add and to the west you subtract. This is false easting which is a west or east measurement based on an imaginary meridian.
-when using false northing or easting this must be noted.
what is SPCS and how do you locate a point using it
SPCS is similar to UTM. Uses NAD 27 and NAD 83, used for city and county data
1.)SPCS is based on state zones, determine the zone you are in
2.)determine northing and easting measurements now in feet
3.)two projections used
-Tranverse Mercator used for north to south oriented states. States using this projection have their baseline origin 500,000 feet to the west of the principle meridian.
-lambert conical- used for west to east facing states. states using this projection have their baseline at 2,000,000 feet west of the meridian.
What is GNSS
GNSS is what more accurately describes GPS. it stands for global navigation satellite system; an overall term for describing technology that uses signals from satellites to find locations on earths surface.
What is GPS
Name orginates from NAVSTAR GPS which was developed by the department of defense as a U.S. global positioning system. Technically GPS only really accurately describes the U.S.
What is NAVSTAR
NAVSTAR is the U.S. global positioning system
What is trilateration and describe how it works and why it needs 4 satellites.
-2dtrilaterion: the process of finding your position relative to three points of reference.
-3dtrilateration:the process of finding a location on Earth’s surface in relation to the positions of three satellites
-how it work: A receiver is finding its position relative to three satellites and using the intersections of these 3d circles to determine where you are located.
-Why we need 4 satellites: only 3 satellites are actually needed to find where you are but a 4th satellite is needed to correct for errors in the receivers clock. this is because most receivers don’t have atomic clocks. The position you recieve is measured using WGS84
What are the three basic components of NAVSTAR GPS and describe each one
1.)space segment: Made of numerous satellite’s and the signals they broadcast
2.)control segment: The series of worldwide ground stations that receive signals and report back to the master control station at Schriever air force base in Colorado
3.)user segment: consists of GPS receivers on the ground that pick up signals. Receivers can only receive signals it CAN NOT transmit back
which datum does NAVSTAR GPS use
WGS84
what frequency can single and duel receivers pick up.
single: L1
dual: L1 and L2
The use of a base station or other earth-bound source to transmit a correction signal to a GPS receiver is known as __________.
DGPS (Differential GPS)
Of the following locations, where is a user most likely to experience multipath errors? Select all that apply.
-a city street lined with tall buildings
-a stream running through a deep canyon
-a tree-covered hiking trail
-an open field of soybeans
-a city street lined with tall buildings
-a stream running through a deep canyon
-a tree-covered hiking trail
What is the official name of the U.S. global positioning system?
NAVSTAR GPS
What component of GPS includes the series of ground stations that help maintain GPS?
control segment
Which statement is correct concerning GPS signals and codes?
a.)The C/A and P codes are transmitted on L1 and L2.
b.)The C/A code is transmitted on L1 and L2, and the P code is transmitted on L2.
c.)The C/A code is transmitted on L1, and the P code is transmitted on L1 and L2.
d.)The C/A code is transmitted on L1, and the P code is transmitted on L2.
The C/A code is transmitted on L1, and the P code is transmitted on L1 and L2.
When do multipath errors occur?
when the GPS signal is reflected from local objects, causing the signal to be delayed
Of the following, what methods can be used to improve the accuracy of GPS positional measurements? Select all that apply.
-CORS
-FAA
-DGPS
-GPX
-DGPS
-CORS
Which of these is designed to operate in Japan?
-BeiDou-2
-Eisei
-IRNSS
-QZSS
-QZSS
Who has access to the P code?
military personnel
What is PDOP
error introduced by poor satellite arrangement. Lower value = better. Caused by geometric position.
-typically 5 meters off
-the further satellites are from one another and the wider the angle the more accurate measurements will be.
what is differential correction. (DGPS)
differential Gps: a method of using a ground-based correction in addition to satellite signals to determine position.
-because base station knows its own coordinates it is able to provide correction
-reduced to 5 meters or less