Text Flashcards
geospatial technology
a number of different hightech systems that aquire, analyze, manage, store, or visualize various types of location-based data
-anything using information with location associated with it
GIS
Geographic information system
.computer based set of hardware and software used to capture analyze, manipulate, and visualize geospatial information
-computer based mapping, analysis, and retrieval of location based data
. Term GIS first appeared in 1960s with the implementation of CGIS(Canadian Geographic Information System), which was designed to provide large scale mapping of land use in Canada
Remote sensing
axquisition of data and imagery from the use of aircraft and satellites
sattelite imagery
digital images of earth acquired by sensors onboard orbiting spaceborne platforms
aeriel photography
acquisition of imagery of the ground taken from an airbourne platform
Global positioning system
GPS
-acquisition of real time location information from a series of sattelites in earths orbit
GEOINT
Geospatial intelligence
-geospatial technology used for military
Geospatial data(spatial data)
items that are tied to specific real world locations
-location based data
-
non-spatial data
data that is not directly linked to a geospatial location (such as tabular data)
-names of occupants, value of a house, value of land
The National Map (US)
an online basemap and data viewer with downloadable geospatial data maintained and operated by the USGS and part of the national geospatial program
GISci
Geospatial information science or Geospatial technologies
crowdsourcing (citizen science)
the activities of untrained volunteers too create content and resources that can be utilized by others
geolocation
the technique of determining where something is in the real world
- use of IP address of device
- wifi connection
- cell towers your phone is connected to
- gps reciever
W3C Geolocation API
the commands and techniques used in programming to obtain the geolocation of a computer or mobile device
geotag
connecting real-world location information to an item
-ex: picture, photo
virtual globe
a software program that provides an interactive three dimensional map of earth
datum
a reference surface or model of Earth that is used for plotting locations anywhere on the actual surface of the earth
-representes the size and shape of earth, which contrary to popular belief is perfectly round
-earth actually ellipsoid or spheroid (larger at center then poles)
-mathematical model against which to reference locations and coordinates
100s of datums in the world
-some measure whole world and others just regions or countries
-measurments from one dont always match with another
Earth is actually ____ or _____ not a perfect sphere
ellipsoid, spheriod
geoid
a model of earth using mean sea level as a base
-tries to account for differences in earths shape which is augmented by gravities pull
Geodesy
the science of measuring Earths shape
-to develop models and reference surfaces
NAD27
The North American Datum of 1927
. this datum was developed for measurments of the United States and North America. It has its center point positioned at meades ranch in Kansas
NAD83
The North American Datum of 1983
. This datum was developed by the National Geodetic survey, together with Canadian agencies, and is used as the datum for much data for the US and the N.A continent as a whole
. NAD83 is very commonly used, the US national geodetic survey is currently preparing a new datum to take its place, but it wont be ready until 2022
WGS84
The World Geodetic System 1984
. This datum was developed by the US department of defense and is used by the Global Positioning System for locating points worldwide on Earths surface
datum transformation
is required to alter the measurments from one datum to another
. is a computational process, a standard one in many geospatial software packages
. Datums can be used to set up geographic coordinate systems (GCS) for measuring coordinates
Geographic Coordinate System
GCS
.a global reference system for determining the exact position of a point on earth
. a set of global lat and long measurments used as a reference system for finding locations
.GCS measurments are in degrees minutes and seconds
Latitude
imaginary lines on a globe north and south of the equator that serve as a basis of measurement in GCS .aslo referred to as paralells . run east to west direction .equator serves as point zero - 0 to 90
Longitude
. run north to south
. Prime meridian serves as starting point of zero
. imaginary lines on the globe east and west of the prime meridian, they serve as basis of measurment in GCS
- 0 to 180
degree= \_\_ minutes second= \_\_ seconds
60,60
1 single minute of lat is equal to about __ nautical mile
distance between degrees of longitude varies at different places on earth, lines of long get closer together as hey approach the ____ and are farthest appart at the _____
1
poles, equator
lines of latitude are measured in angular units from the ______ while lines of longitude are measures in angular units from the ______
Equator
Prime Meridian
Prime Meridian
the line of longitude that runs through greenwhich england and serves as the 0 degree line of longitude from which to base measurments
decimal degrees
. the fractional decimal equivalent to coordinates found using degrees, minutes, and seconds
__ degrees of longitude per hour
15
15 x 24= 360
International Date Line
marks the devision between 24hour periods and divides one day from another, but it also bends to accomodate considerations of geography, political boundaries, and conveniance, and makes detours to include islands in one time zone or another rather then strictly following the line of the 180th meridian
map projection
the translation of locations on the three dimensional earth to the 2 dimensional surface
4 types of map projection distortions
direction, shape, size, distance
Mercator Projection
. developed in 1569 by Gerardus Mercator
.for use in navigation aid
-designed so every straight line on the map was a line of constant directio
-shapes are kept intact
-sizes are very distorted and become more distorted as you move further form the equator
Three main developable surfaces that are used in map projection are:
cylinder -which creates a cylindrical projection cone -which creates a conical projection Flat plane -creates an azimuthal surface
Point of _______, where the Earth touches the surface
tangency
-where map distortion is at its least
Lambert Conformal Conic
. conic projection
.cone intersects earth at two paralells
-commonly used for geospatial data about the US and other East-west trending areas
Transverse Merctor
. cylindrical projection
. tangency pooint being the intersection between the cylinder and earth
.tangency points are the poles as it wraps around the poles and not the equator
-used for more North-south trending areas
UTM
Universal Transverse Mercator
. the grid system of locating coordinates accross the globe
.devides the world into a series of zones, and then determining X and Y coordinates for a location in that zone
.set up by trnaslating real-world locations to where they coresponding places would be on a two dimensional surface (using transverse mercator projection)
. only covers Earth from between 84 degrees N latitude and 80 degrees S lat
-CANT BE USED FOR MAPPING POLAR REGIONS
.Universal Polar Stereographic Grid System is used for polar regions
.UTM uses meters rather then degrees minutes and seconds
.display UTM coordinates East/west, North/south, and then the zone
T OR F
UTM cant be used for polar regions?
T
Universal Polar Stereographic Grid System is used for polar regions
UTM zone
.globe devided into 60 UTM zones each one 6 degrees of longitude wide and set up as its own cylindrical projection
. Zones 1-60 begin at the 180th meridian and move east
ex: Mount rushmore is zone 13
beijing is zone 56
easting
northing
. UTM uses meters rather then degrees minutes and seconds
. UTM’s X and Y coordinates are referred to as:
a measurment of so many units east(or west) of some principal meridian
- measure from central meridian in the zone’s center which is given a value of 500,000 meters, measurments are made to the east(adding meters) or west(subtracting meters) from this value
- no zone is more then 1,000,000 meters wide so no negative values
- based on false easting (imaginary central line)
northing is found by counting the number of meters the point is north of the equator
-for instance mount rushmore is located 4,859,580 meters to the north of the equator
-if in the south, dont use negative northings, take the number of meters south and add 10,000,000 to the total
= -3,747,732+10,000,000= 6,252,268
. the 10,000,000 is kknown as the false equator which you can measure from
false northing
a measurment made north(or south) of an imaginary line such as is used in measuring UTM northings in the southern hemisphere
false easting
500,000 meters central line in a zone
-measurments made east or west of this imaginary line
United States National Grid
uses more complicated UTM to pinpoint more accurately a location
-used by feds in US
SPCS
State Plane Coordinate System
. another grid based system for measuring and determining coordinates
.Used in US for data, especially city and countt data and measurments
.SPCS data was originally measured using the NAD27 datum, but now there are datasets using the NAD83 datum.
. requires a specified zone, easting, and northing in addition to the state in which the measurments are being made
.SPCS zones are formed by following state or county boundaries
-each state often has multiple zones
.identify state, then zone
.each zone has pretermined baseline and principle meridian
. two types exist, one using the transverse mercator for north-south states and one using lamberts conical version for east-west states
.listed as: false easting, false northing, state, and zone
CGIS, GIS, was originally developed by Canadian ____ _______; the father of GIS
Roger Tomlinson
In GIS there are two ways of viewing the world
Discrete Object view:
. the world is made up of a series of objects, each of which has a fixed location, or a fixed starting and stopping point, or some sort of fixed boundary
.represented by one of three objects:
points-zero dimensional objects, simple coordinates
lines-these are one dimensional objects, created from connecting starting and ending points (and any points in between that give the lines its shape)
polygons-these are two dimensional objects that form an area from a set of lines (or having an area defined by a line forming a boundary)
GIS vector objects
.are used to model real-world phenomena using a vector data model
points-zero dimensional objects, simple coordinates
lines-these are one dimensional objects, created from connecting starting and ending points (and any points in between that give the lines its shape)
polygons-these are two dimensional objects that form an area from a set of lines (or having an area defined by a line forming a boundary)
vector ____ make up the basis of the GIS vector ____ ______
objects
data model
GIS vector data model
is a means of representing and handling real world spatial information as a series of vector objects-items are realized in the GIS as points, lines, and polygons
Digitizing
is a common way to create points, lines, and polygons of vector data
-in essence you are tracing or sketching over the top of areas on the map or other image to model features in that map or image in the GIS
heads up digitizing- a map or other image(usually ariel photography or sattelite image) is displayed on the screen as a backdrop
on-screen digitizing-
topology
the notion of the GIS being able to understand how objects connect to one another independent of their coordinates
-eastblishes adjacency(how one polygon relates to another polygon, in that they share a common boundary, connectivity(how lines can intersect with one another, and containment (how locations are situated inside of a polygon boundary)
discrete object view
a conceptualization of the world in which all reality can be represented by a series of seperate objects
continuous field view
a conceptualization of the world in which all items vary accross Earths surface as constant fields and values are available at all locations along the field
- not everything has a fixed boundary or is an object
ex: temperature, atmospheric pressure, and elevation
Raster data model
data is represented using a set of evenly distributed grid cells, with each square cell representing the same area on the earths surface
-when continuous fields are represented and the three vector objects are not affective
.each grid cell must be the same size
.each grid cell contains one single value
ex: National Land Cover Database
grid cell in raster data model
a square unit representing some real-world size which contains a single value
