Lectures Flashcards
Geomatics defined
•Geomatics is a field of activities which, using a systemic approach, integrates all the means used to acquire and manage spatial data required as part of scientific, administrative, legal and technical operations involved in the process of the production and management of spatial information.
5 key parts of geomatics
measurement, analysis,
management, storage and display
spatial data
Directly or indirectly referenced to a location on the
surface of the earth
• Space / Place • Almost everything around us can be referred to as Spatial Answers: what is where? Where can something be found? Why something happens there, not elsewhere?
non spatial data
Cannot be related to a location on the surface of the earth is referred as non spatial data.
Describe differences between :
Geographic information systems
Spatial info systems
land information system
GIScience
Geographic information systems
• properly emphasizes geographic component
• minimizes computer science
Spatial information systems
•perhaps focuses too much on “information systems”
Land information systems
• deals with the cadaster
-land info for real estate
GIScience
•emphasizing computer science aspect (focusing on big data management, geo-visualization and incorporating both GIS,Remote Sensing
Data vs. Information
Data vs. Information:
. information is pulled from a pool of data
. data is the bare results
-when you play with data it becomes information
8 subject areas in geomatics
Surveying and mapping Geodesy and Gravimetry Land information management Positioning and navigation (GPS, GLONASS etc.) Cartography & digital mapping Geographic information systems Remote sensing (aerial/satellite/ground based) Photogrammetry
data from original GIS was stored on
Stored on magnetic tape (digital)
words transferred into numbers for storage
Geodesy
4 parts
A scientific discipline determining the shape,
size, rotation and gravity field of planet Earth,
including their variations in time.
Why is Geodesy important
• Accurate positions are required for a wide variety of
applications; including:
surveying, mapping and navigation, remote
sensing, mineral exploration, flood risk
determination, transportation, land use,
ecosystem management..
• Studying plate movement, subsidence of land, sea
level rise, movement of glacier and changes in
cryosphere………
Geodesy derived from greek words for _____ and the saying I devide and measure
derived from the Greek for ‘earth’ and ‘I divide and
measure’ and refers back to ancient Egyptian land
surveying techniques.
_______ believed the earth was flat in _th century bc while ______ in _th century bc realized it was spherical
_____ in ___ BCE was the one who truly got the sphere idea going
Homer-8
Pythagoras- 6
Aristotle (384 BCE)
Ancient Measurment of Earth:
• _______ made more
explicit measurements,
_______ miles.
Currently accepted
circumference is _______
miles
• Eratosthenes made more
explicit measurements,
25,000 miles.
Currently accepted
circumference is 24,901
miles
The Well Theory:
who came up with it?
What does it mean?
Eratostenes
.he realized when the sun is directly above a deep well in one city you could stand in a nearby city to the north and measure the angle of the shadows and multiply by the distance between the cities
shadow angle x distance= circumference
Geodesy was born
Two different types of remote sensing
Two different types of remote sensing:
.Active and inactive
.Active send energy towards an object allowing it to work at any time of day
. inactive uses the suns energy
Triangulation
(in surveying) the tracing and measurement of a series or network of triangles in order to determine the distances and relative positions of points spread over a territory or region, especially by measuring the length of one side of each triangle and deducing its angles and the length of the other two sides by observation from this baseline.
Equitorial Circumference=
Polar Circumference=
40,075 km
40,008 km
difference of 67 km
4 physical concepts affecting geodesy
Earths motions
Relationships in solar system
Plate tectonics
Gravity
Circle = ______
Real Shape of Earth=_____ / _____
Shape based on average water levels=
sphere
ellipsoid/spheroid
geoid
Ellipse->______/______ because of…
When the revolving oval is a perfect ellipse, the solid generated by the revolution is called the ellipsoid/ (Spheroid).
defining a spheroid
A spheroid is defined by either the semimajor axis, a, and the semiminor axis, b, or by ``a`` and the flattening. • The flattening f, is derived as follows: f = (a - b) / a • The flattening is a small value, so usually the quantity 1/f is used instead. • The flattening ranges from 0 to 1. A flattening value of 0 means the two axes are equal, resulting in a sphere.
describe the flattening
The flattening ranges from 0 to 1.
A flattening value of 0 means the
two axes are equal, resulting in
a sphere
Datum
• Datum is a reference point, surface, or axis
on an object against which measurements
are made
• A geodetic Datum is a reference from
which spatial measurements are made….
• A spheroid/ellipsoid approximates the shape
of the earth, a Datum defines the position of
the spheroid relative to the center of the
earth.
A mathematical surface (spheroid/ellipsoid) is used to approximates the shape of the earth, a Datum defines the position of the spheroid relative to the center of the earth.
define geodetic datum
A geodetic Datum is a reference from
which spatial measurements are made….
The international ellipsoid was developed by Hayford in ____ and adopted by the International Union of Geodesy and Geophysics (IUGG) which recommended it for international use.
1910
GRS80
A unified geodetic system for the whole world became
essential for several reasons:
advancement of space science and astronautics
lack of inter-continental geodetic information
need for global maps for navigation, aviation, and
geography and basis for a worldwide geo-data
• GRS80 was adopted by the International Association of Geodesy (IAG) in 1979.
• Become as origin of the WGS84 (World Geodetic
System), however, WGS84 refined afterword.
datum-coordinate system relationship?
• So, a Datum defines how a coordinate system is
seated over the ellipsoid/spheroid.
• The origin of the new NAD83 system is the centre
of mass of the Earth, and uses the ____ ellipsoid
GRS80
GPS receivers also use the centre of mass of the
Earth as their system’s origin, uses ______
system.
WGS84
NAD27
The old North American Datum 1927 (NAD27) had
a different origin, making it useful only in North
America.
T OR F
For all practical applications WGS84 ellipsoid and GRS80 ellipsoid are identical.
T