Cartography Basics

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Cartography Basics Map Projections Datums Coord
inate Conversion Modtran Resampling
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Map Projections
Spherical earth model Latitude, Longitude,
Altitude Meracator Projection Universal
Transverse Mercator (UTM)Projection zone,
easting, northing, altitude UTM Military Grid
Global Coordinate System (GCS)
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DATUMS
b
Geodetic latitude
a
DATUM WGS 84 Semi-major axis a
6378137.000m Semi-minor axis b
6356752.314m Flattening f 1/f (a-b)/a
1/298.257223563
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DATUM TRANSFORM
Lat/long/alt in datum 1
Same Lat/long/alt in different Datum
Same earth point has different lat/long/alt in
a different datum
The same lat/long/alt numbers in two different
datums refer to two different points on the
earth. A Datum Transform converts the same point
on the earth from lat/long/alt in one datum to
lat/long/alt in second datum.
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asemi-major axis 1/f reciprocal of flattening
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Coordinate Conversion
Projection 1 Datum 1
Projection 2 Datum 2
lat
long
Zone, Easting
Easting E(lat,long,alt,datum_parameters) Zone
Z (lat,long,alt,datum_parameters) Northing
N(lat,long,alt,datum_parameters) Alt
A(lat,long,alt,datum_parameters)
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Modtran execution EXAMPLE
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Resampling
Projection 1 Datum 1
Projection 2 Datum 2
lat
long
Zone, Easting
V(Easting,Zone, T(V(lat,long,alt,datum_pa
rameters), Northing, Alt
V(lat,long,alt,datum_parameters), datum_paramete
rs) V(lat,long,alt,datum_parameters),
V(lat,long,alt,datum_parameters))
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Resampling Algorithm
1) Get point of interest P 2) Transform to
coordinates P T(P) in which data is
available 3) Find surrounding data Values
V(P1),V(P-1) 4) Interpolate from surrounding
values to the Value at the transformed
point V(P) I(V(P1),V(P-1),) 5) Assign the
interpolated value to the point of interest
V(P) V(P)
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Interpolation Nearest neighbor Truncate Bilinea
r Interpolation
V(x,y) V(x,y) V(x?x,y) - V(x,y)(x-x)/((x
?x)-x) V(x,y1) V(x,y ?y) V(x ?x,y ?y)
- V(x,y ?y)(x-x)/(?x) V(x,y) V(x,y)
V(x,y ?y) - V(x,y) (y-y)/(?y)