Ch4 Flashcards
T or F
Geographic coordinate systems are based on spherical coordinates and measured in latitude and longitude
T
T or F
A geoid shifts the ellipsoid relative to the datum to achieve a best fit between the two
F
A datum shifts the ellipsoid relative to the geoid to achieve a best fit between the two
Three Types of Projections are _____ , ____, and ______.
Azimuthal, cylindrical, conic
Projections all distort one or more properties of
______ , ______, _______, and ________
distance, direction, shape, area
T or F
UTM coordinate system breaks the world up into 6 zones of 60 degrees each
F
UTM coordinate system breaks the world up into 60 zones of 6 degrees each
What is data called that has a defined coordinate system?
georeferenced
Match the type of coordinate system to the definition:
Unprojected
Projected
Based on spherical coordinates
Converts spherical coordinates to planar coordinates
Unprojected (geographic)- Based on spherical coordinates
Projected- Converts spherical
What type of coordinate system is measured in lat & long?
unprojected/geographic
A _________, or GCS, stores locations in longitude-latitude values
geographic coordinate system
An _______ is a smooth shape with a slightly smaller north-south axis
ellipsoid
A ______ is a surface modeled from gravity differences and is closest to the true shape, but is too complicated for mapping
geoid
A _______ shifts the ellipsoid relative to the geoid to achieve a best fit between the two.
datum
A _____ optimizes the shift of geoid to ekkipsoid for the best fit at a particular location. It may also use a surveyed network of points to make further adjustments.
local datum
A _____optimizes the fit for the entire earth btwn the geoid and ellipsoid.
geocentric or world-centered datum
A datum definition includes what 2 things:
- The particular ellipsoid used based on a determination of the earth’s major and minor axis
- The adjustment or fit (translation of center)
___is a mathematical conversion of points on the earth’s surface to a flat plane (map)
projection
what are the 3 projection types?
cylindrical, conic, azimuthal
Cylindrical projections usually preserve ______ and ______
direction and shape
Conic projections usually preserve _____and/or _____
distance, area
Azimuthal projections usually preserve ____and/or ______
area, distance
How many standard parallels does a secant projection have?
2
a common coordinate system for large-scale maps is?
UTM coordinate system, state plane CS
Name one way the coordinate system used to store the data can impact the results of an analysis
areas or distances can be incorrectly calculated
Proper alignment of data sets requires that each one have a label that records the complete coordinate system parameters
This label is called the ________
Spatial Reference
The ______tool is used to permanently convert a data set from one coordinate system to another
Project
________creates a new data set in the new coordinate system
projection
Create the missing label for the true coordinate system of a map with the_____tool
Define Projection
what tool Use only when CS is missing or incorrect?
define projection
What tool should be used when changing a CS permanently?
project tool
What tool is use to assemble collections of data with the same stored CS.
project tool
The _______ of the data layer is the range of x-y coordinates of the features actually in the feature class.
extent
Values between +180
and –180 indicate an ______GCS coordinate system with map
units in degrees, whereas large values indicate a ______ coordinate
system with units of feet or meters.
unprojected, projected
What is is the selected x,y values and units for a map?
The coordinate space
_________ measures east-west angles ___________ measures north-south angles above the equator
Longitude (X), from the Prime Meridian.
Latitude (Y)
____ are the basis for coordinate systems
Projections
How can The coordinate system used to store the data impact the results of an analysis?
Areas or distances may be incorrectly calculated
What units are determined by the coordinate system chosen for the map
Map units
What units are the x-y values stored in the file
Stored units
What is the name of the label that records the complete coordinate system parameters?
spatial reference
What is the x-y precision in the spatial referencfe?
resolution
