
GIS BOOTCAMP. Todd Bacastow. Geography matters!. ‘Geographic Information’ is information which can be related to specific locations. Most human activity depends on geographic information. Topic 1: What is GIS?. Dozens of possible definitions Some emphasise the technology The Hardware
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Todd Bacastow
Cartography
Remote Sensing
Photogrammetry
Surveying
Geodesy
Statistics
Operations Research
Computer Science
Mathematics
Civil Engineering
Business management
Behavioural science
Etc….
GIS is the convergence of many disciplines:DXF and DWG
NTF
DLG
TIGER
SDTF
DIGEST
.E00 (Arc Export) format
Shapefiles
For Raster data
BIL
BSQ
DEM
TIFF
JPEG
BMP
Some popular standards for digital map data includeRegular tessalations
Rasters
Irregular tessalations
Quadtrees
Voronoi Tessalations
Triangulated Irregular Networks (TINs)
Datums, and Projections
Northern
Hemisphere
Eastern
Hemisphere
Equator
0º Latitude
Prime Meridian 0º Longitude
Western
Hemisphere
Southern
Hemisphere
90º S Latitude
90º W Longitude
90º E Longitude
0º Longitude 180º Longitude
Spherical CoordinatesSpherical “grid” is called a graticule
Latitude references north and south
Longitude references east/west
Line of constant latitude is a parallel
Line of constant longitude is a meridian
Meridiansconverge at the poles
Latitude range: 0 to 90 degrees north and south
Longitude range: 0 to 180 degrees east and west
A spherical coordinate measure is expressed in degrees (º), minutes (‘) and seconds (“)
1º = 60’ = 3,600” ; 1’ = 60”
Expressed as:
ddd mm ss N/S, ddd mm sss E/W
Note the convention is to express latitude (y) before longitude (x), but computer environments use x,y
Western and Northern
Hemisphere: -x, +y
Eastern and Northern
Hemisphere: +x, +y
Western and Southern
Hemisphere:-x, -y
Eastern and Southern
Hemisphere:+x, -y
GRS80 Spheroid
Meades Ranch
Kansas
Earth
Center
Clarke 1866
Center
Clarke 1866 Spheroid
Horizontal DatumNAD 1983 DATUM
Meades Ranch
Kansas
GRS80 Spheroid
Earth
Center
Clarke 1866
Center
Clarke 1866 Spheroid
Sea Level
Sea Floor
Vertical Datum
(mean sea level)
Vertical DatumTo represent a spherical model of the earth on a flat plane requires a map projection!
Projection
b
o
a
Y
a
X
Map ProjectionsSpheroid: a three-dimensional geometric surface generated by rotating an ellipse about one of its axes.
It provides an approximate model of the earth’s shape, the first step in constructing a projection
C
B
M
E
A
C
D
84º 30’
500,000 mE
320,000 mE
680,000 mE
0º 00’ 00”
80º 30’
B
M
E
Universal Transverse Mercator (UTM)D
0 mN
10,000,0000 mS
72º W
75º W
84º W
78º W
81º W
v
v
Standard Meridian
Standard Meridian
Standard Meridian
Central Meridian
Central Meridian
UTM ZONE 17
UTM ZONE 18
Standard Parallel
77º 45’W
41º 57’N
Scale: .9999568
Central Parallel
41º 25’N
Scale: 1.000000
Standard Parallel
40º 53’N
Projection Origin
40º 10’N, 77º 45’W
Central Meridian
Pennsylvania State Plane North ZoneCentral Meridian
Scale: 1.000000
Standard Parallel
40º 58’N
Scale: .9999595
Central Parallel
40º 27’N
Scale: 1.000000
Standard Parallel
39º 56’N
Projection Origin
39º 20’N, 77º 45’W
Pennsylvania State Plane South Zoney max 771,700’
x min 1,204,600’
y min 162,000’
2,000,000’
x max 2,813,400’
y max 677,900’
x min 1,188,150’
y min 153,500’
2,000,000’
Pennsylvania State Plane Origin Offsets For North and South ZonesX offset: 2,000,000’
y offset: 0’
projection origin for both Zones: 2,000,000’, 0’
2.5/500*12 = 2.5/6,000 = 1:2,400
1.82” on map: 1 * 1.82 = 4,800*1.82
1.82” = 8,7376” = 728’
30’
15’
f(scale) =
Map ScaleLARGER SCALE
1:60,000
SMALLER SCALE
1:8,000,000