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24 Cards in this Set
- Front
- Back
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113.125 degrees west
(decimal degrees) |
113 D 7 ' 30''
(degrees minutes seconds) |
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Relative & absolute
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relative- with respect to another place (street address or direction)
absolute- fixed with respect to an orgin (equator and prime meridan 0,0) |
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locational systems
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measuring systems by which we can define the absolute location of features on the earth
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latitude
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FLATITUDE ------
ranges from 90d N thru 0 at equator to 90d S = (180 d total) |
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longitude
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ranges from 0 at prime meridian to 180 d E at Internation Data Line (greenwich, england) then 180W to 0 at prime meridan (360 D total) |
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NSEW
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N +
S - E + W - NY/NE = 75 dW |
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Reference Grids
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flat maps
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Cartesian coordinate systems : civilian system
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false origin
-500,000 meters west of the central meridian of each UTM zone -in N. Hem the false origin is located on the equator -S. Hem false origin is located 10,000,000 meters south of the equator -Notation (easting in M, northin in M; zone, hempisher) ex. 305,904 -4,771,651; 16, N |
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Universal Transverse Mercator System
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system of projections but must know what zone in
-62 zones and measured in meters -covers earth's surface between 80dS and 84dN -Universal Polar Stereographic UPS is sused for the polar caps -UTM establishes 60 NS zones each 6d longitude wide (each zone over laps half a degree to adjacent zone) (or 30 minutes on each side) -NS extent = transverse mercato -EW = conic projection -northings ranges from 0m at equator and reaches 10,000,000 m at the poles -eastings have a false origin outside the western limit of zone (about .5 degress) central meridian of the zone has easting of 500,000 m E -identical to civilian system but uses a grid referene system to identity locations (georef) -3n, wj wuold indicate a 10k area on the earth |
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Military Grids
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within zones, 8 d strips of latitude are designated by an alpha character from c to x
-a single rectangular area of 6x8 degrees is designated by numeric longitudianl zone, then alpha latiudinal zone -within 6x8 degrees areas, subdivided into squares of 100,000 meters on a side. lettered from a to z both north south and east west -within smaller squares locations are given by pairs of x,y digits |
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state plane coordinate systems
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rectangular coordinate systems
-applied individually to each of the united states (michigan has three SPC grids - North central south) -false easting/false northing -measuing in feet -follow county boundaries within states |
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specialized state systems
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creates single zone, rather than multiple zones (ex michigan georef & idaho transverse mercator)
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public land surveys
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townshps, range, or section
-basic unit is acre -defined on the ground, not on a grid superimposed on a map -baseline and principal meridian defined on the ground -6 mi squared desinged by townshp number NS of base line and range number EW of principal meridan -section, == one of the 36 mile square sections -still used in legal descriptions: POB , PLS used for real estate, metes and bounds- meters are the corner and bounds are inbetween metes |
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georeferencing
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the process of assigning a geogrpahic location (lat/long) to a geographic feature on the basis of its address
-important tool for emergency response, delivery, marketing, crime analysis, real estate, navigation -digital record for the feature must have a field which can be linked to a geographic base file with known geographic coordinates |
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problems with georeff.
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-lacks street names (po boxes)
-human erroes in address records -inconssistancy of address -updating |
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LAT n LOng
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used to record spherical and global location
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UTM
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global system divided into 60 zones
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STate plane coordinaes
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US only and higher accurary
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position is related to shape of earrth
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-modeled as ellpsoid/spheriod
-accurate positioning requres knowledgeof the datum used to construct a coordinate system |
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Projection
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a system in which locations on the curved surface of the earth are displayed on a flatsheet or surface according to some set of rules
-classified by surface/case/aspect/preserved properties -understanding of distortions associated with projections |
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projections pt. 2
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a set of complex equations that move to transform from spherical world to flat map and then back. consistant way to run equation taking us from one place to the other. conceptually looking to go from sphere in simple for to something flat.
1 Flat represesntation (planar) - developable surface. paper 2. cylinder CYlindrical - normal = right side up, transverse = sideways 3. cone CONiCAl |
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geodatabase
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collection of spatial data feature classes (set of likes like eacother, group by class belong to .. share some coordinate system)
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arc catalog
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use to create geodatabase , set up, and source data
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4 scales of measure
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nominal- church/house
ordinal- allows us to sort, supports greater than or less than interval- counting integers (greater than or less than) |
