gis midterm Flashcards
what is data
refer to facts, measurements, characteristics, or traits of an object of interest
difference between data and information
data describes the object of interest, information is the knowledge resulting from data through analysis/collection/interpretation
primary data
collected directly/on a firsthand basis
secondary data
collected by someone else
nominal data
name data; gives data a name but there’s not really a way to compare data. ex eye color, ethnicity, land use
ordinal data
order data; gives ranks to data. ex very good, good, neutral, bad, very bad
interval data
measures precise quantitative data. ex temp, year
ratio data
measuring data by comparing it to the data collected elsewhere. ex population density
database management system
a software package that allows for the creation, storage,
maintenance, manipulation, and retrieval of large datasets that are distributed over one or more files
database
structured collection of data files
flat database
spreadsheet where all data is stored in a single large table
hierarchical database
organizes data into a “one to many” associations across levels (looks like a family tree)
network database
similar connections to hierarchical but a top level with categories and bottom level with items that fit into the categories with lines going kinda everywhere
primary key
represents the attribute (column) whose value
uniquely identifies a particular record (row) in the relation
(table). allows no duplicate values and cannot be null
foreign key
The primary key corresponds to an identical attribute in a
secondary table
origin table
where the primary key can be found
destination table
where the foreign key can be found
vector data model
uses points and their x-, y-coordinates to represent discrete
features
raster data model
uses a grid and grid cells to represent continuous features
such as elevation and precipitation
mental map
psychological tools that we use to understand,
relate to and navigate through the world where we live, work and play
reference map
deliver location information to the map user
thematic map
concerned with a particular theme or topic of interest
dynamic map
changeable or interactive representations of the earth
location
position on the surface of the earth
nominal location
location by name. ex cudahy library
relative location
location by some reference. ex next to the lakeshore
absolute location
location by longitude/latitude or by address
true north
where the axis of the earth’s rotation intersects the
earth’s surface. where N and S poles are used as benchmarks
magnetic north
the point
on the surface of the earth where the earth’s magnetic fields
converge. not exactly the same as true north/north pole
grid north
the northward
direction that the grid lines of latitude and
longitude on a map, called a graticule, point
to
distance
The degree or amount of separation between
locations and can be measured in nominal or absolute
terms with various units
map scale
factor of reduction of the world so it fits on a map
representative fraction (RF)
describes scale as a simple ratio. The numerator,
which is always set to one (i.e., 1), denotes map
distance and the denominator denotes ground or
“real-world” distance.
written scale
uses words to show the relationship between the map and the landscape it depicts
graphical scale
a symbol which appears as a small ruler printed on the
margin of the map
geographic coordinate system
location reference system for locating spatial features on the Earth’s surface
latitude
angular distance north or south of the equator, measured from the center of Earth
parallels
A line connecting all points along the same latitudinal angle
longitude
measures the angle created between the point of interest, the center of the Earth at the same parallel of latitude, and a point on that latitude along the arbitrarily defined prime meridian
equator
largest line of latitude, measured at 0 degrees
great circle
divides globe into equal halves and passes thru center
small circle
splits globe into unequal portions and doesn’t pass thru center
latitude based geographic zone
arctic, subarctic, midlatitude, subtropical, equatorial and tropical
meridian
imaginary north to south lines (not full circles), denote west to east position from prime meridian
prime meridian
meridian that all others are measured the distance from
small-scale map
covers a larger geographic region such as the world
large-scale map
covers a relatively small geographic area, such as a 7.5’ quadrangle map
datum
defines the position of the spheroid relative to the center of the earth
why are datum important
it provides a frame of reference for measuring locations on the surface of the earth and a shift of the datum will result
in the shift of positions of points
NAD 83
horizontal and geometric control datum for the United States, Canada, Mexico, and Central America
WGS 84
the current standard used in cartography, geodesy,
and satellite navigation including GPS
map projection
transforms the geographic coordinates on an ellipsoid into locations on a plane, produces a systematic arrangement of parallels and meridians on a flat surface
planar projection
When the plane of projection taken is a simple 2-dimensional plane
cylindrical projection
When a right circular cylinder is taken as a developable surface
conical projection
When right circular cone is taken as a developable
surface
equal area projection
Area on a segment on the generating globe is truly preserved on the corresponding segment of the graticule
conformal projection
Here the shape of a segment on the generating globe is truly preserved
equidistant projection
Distance between any two points on the generating globe is truly preserved
azimuthal projection
Here, the azimuth or bearing denoting the directions between any two points on the generating globe is truly preserved
map projection parameters (6)
✓ standard lines (standard parallels and standard meridians),
✓ principal scale,
✓ scale factor,
✓ central lines,
✓ false easting, and
✓ false northing.
mercator projection problem
poles size are largely exaggerated
key elements used to make NY 9-11 basemap
city streets, properties, building footprints, transportation
networks, rivers, and other waterways
why was Leidner called to help after 9-11
oversaw the city’s advanced GIS
