CARTOGRAFIE
INLEIDING
Opm: 1° (evenaar) = 111 km vs 1° (noordpool) = 0km
Lambert more accurate for Belgium
SOORTEN (SRS, CRS)
WGS 84 (GPS): USA
ETRS 89: EU
Lambert 72: Belgie
Lambert 2008: nieuwe data over belgie
HTAW: hoogte
GEODESY
= mathematical foundation for Geo-Sciences (geography, geology, archeology…)
Old definition: The science of the measurement and mapping of the Earth’s
surface
New definition: the science of accurately measuring and understanding the
Earth's geometric shape, orientation in space, and gravity field, as well as the
changes of these properties over time
1
,THE CORE ASPECT
= To precisely assign the coordinates of a place on the Earth’s surface
Spatial reference system (SRS) or coordinate reference system (CRS)
WGS 84, ITRS, ETRS 89…
SHAPE AND SIZE OF THE EARTH: GEOID, ELLIPSOID
Shape of the earth determined by:
gravitation
centrifugal force (due to the spining of the Earth)
endogenic forces (internal)
exogenic forces (external)
Results:
Earth ≈ ellipsoid (a – b = 21km)
Irregular surface (mathematically indescribable) Veralgemenen
GEOID
GEOID 1
= reference model to approximate the irregular Earth surface
Uses an Equipotential surface (equipotentiaalopp): every point on that surface
has the same gravitational potential value
o Water on an equipotential surface does not flow.
o There exist an infinite number of such surfaces around the Earth
o The plumb line through any surface point is always perpendicular to it
GEOID 2
= A specific equipotential surface (W0) at a same height as the
mean sea level (assumpting that other influences such as winds
and tides are absent) extended through the continents
2
, GEOID 3
= extensive gravitational measurements and calculations on earth’s surface/by satellites
GEOID 4
Need a simple mathematical model to allow positioning, map projection,
practical use: Ellipsoid or Sphere
ELLIPSOID
ELLIPSOID 1
Ellipse with long axis (a) and short axis (b): 3D volume obtained by rotating an ellipse
around the short axis
ELLIPSOID 2
Formule:
BUT: different sets of a and b have been proposed!! #confusion
ELLIPSOID VS GEOID
Geoid: the equipotential plane determined by the mean area of the oceans and the
continuation of this area under the continents
Geoid is used to approximate the irregular shape of the Earth’s surface
Reference ellipsoid: ellipsoid that matches the (local or global) geoid as closely as
possible
Ellipsoid is used to approximate geoid
3
INLEIDING
Opm: 1° (evenaar) = 111 km vs 1° (noordpool) = 0km
Lambert more accurate for Belgium
SOORTEN (SRS, CRS)
WGS 84 (GPS): USA
ETRS 89: EU
Lambert 72: Belgie
Lambert 2008: nieuwe data over belgie
HTAW: hoogte
GEODESY
= mathematical foundation for Geo-Sciences (geography, geology, archeology…)
Old definition: The science of the measurement and mapping of the Earth’s
surface
New definition: the science of accurately measuring and understanding the
Earth's geometric shape, orientation in space, and gravity field, as well as the
changes of these properties over time
1
,THE CORE ASPECT
= To precisely assign the coordinates of a place on the Earth’s surface
Spatial reference system (SRS) or coordinate reference system (CRS)
WGS 84, ITRS, ETRS 89…
SHAPE AND SIZE OF THE EARTH: GEOID, ELLIPSOID
Shape of the earth determined by:
gravitation
centrifugal force (due to the spining of the Earth)
endogenic forces (internal)
exogenic forces (external)
Results:
Earth ≈ ellipsoid (a – b = 21km)
Irregular surface (mathematically indescribable) Veralgemenen
GEOID
GEOID 1
= reference model to approximate the irregular Earth surface
Uses an Equipotential surface (equipotentiaalopp): every point on that surface
has the same gravitational potential value
o Water on an equipotential surface does not flow.
o There exist an infinite number of such surfaces around the Earth
o The plumb line through any surface point is always perpendicular to it
GEOID 2
= A specific equipotential surface (W0) at a same height as the
mean sea level (assumpting that other influences such as winds
and tides are absent) extended through the continents
2
, GEOID 3
= extensive gravitational measurements and calculations on earth’s surface/by satellites
GEOID 4
Need a simple mathematical model to allow positioning, map projection,
practical use: Ellipsoid or Sphere
ELLIPSOID
ELLIPSOID 1
Ellipse with long axis (a) and short axis (b): 3D volume obtained by rotating an ellipse
around the short axis
ELLIPSOID 2
Formule:
BUT: different sets of a and b have been proposed!! #confusion
ELLIPSOID VS GEOID
Geoid: the equipotential plane determined by the mean area of the oceans and the
continuation of this area under the continents
Geoid is used to approximate the irregular shape of the Earth’s surface
Reference ellipsoid: ellipsoid that matches the (local or global) geoid as closely as
possible
Ellipsoid is used to approximate geoid
3
