GEOMATICS Flashcards
What is Geomatics?
Geomatics is the modern scientific term referring to the integrated approach of measurement, storage and display of the descriptions and location of Earth-based data, often termed spatial data.
Earth-based data, of termed spatial data
- space / place
* almost everything around us can be referred to as spatial
Spatial Data
Directly or indirectly referenced to a location on the surface of the earth
Non-spatial Data
Cannot be related to a location on the surface of the earth is referred as non spatial data
Geomatics combines of three elements
- geography
- mathematics
- computer science
Principal subject area comprising Geomatics
- surveying and mapping
- geodesy and gravimetry
- land information management
- positioning and navigation (GPS, GLONASS etc.)
- Cartography + digital mapping
- remote sensing (aerial, satellite, ground based)
- photogrammetry
Where does spatial data come from?
This data comes form many sources, including earth orbiting satellites, air and sea-borne sensors and ground based instruments.
GITECHNOLOGIES
Spatial Data - how to manage/use those?
It is processed and manipulated with state-of-the-art information technology using computer software and hardware
Application of Geomatics?
It has applications in all disciplines which depend on spatial data
- environmental studies
- planning
- engineering
- navigation
- geology & geophysics
- oceanography
- land development and land ownership
- tourism
Canadian Resource Sectors Using Geomatics
-agriculture
-energy
-mining
-environmental protection and management
-land use planning, development & management
-water resource management
-forestry
-oceans and fisheries
health care
location based services
asset management
recreation and tourism
utilities
emergency planning and management
Value of GIS
- providing access to context
- spatial analysis
- spatial modeling
- spatial prediction
Spatial Analysis
using techniques to reveal what is not otherwise visible
Spatial modeling
simulating the action of landscape modifying processes
Spatial Prediction
forecasting where as well as when
Geospatial technology
the sciences, humanities, the general public
GIS is no longer all-encompassing
the 4th edition of Longley et al focuses on GI not GIS
Geography as a discipline
the principles thast make spatial special
the value of a spatial perspective
the importance of integrating data across layers, disciplines
the importance of ground truth
Geodesy definition
A scientific discipline the shape, size, rotation and gravity field of planet Earth including their variations in time
Geodesy important because…
surveying, mapping and navigation, remote sensing, mineral exploration, flood risk determination, transportation, land use, ecosystem management
Where does the word Geodesy comes from
-derived from the Greek for ‘earth’ and ‘I divide and measure’ and refers back to ancient Egyptian land surveying techniques
Ancient measurement of Earth
- plato determined the circumference of the earth to be 40, 000 miles
- Archimedes estimated 30, 000 miles
- Eratosthenes made more explicit measurements, 25, 000 miles
- currently accepted circumference is 24, 901
Physical concepts of Geodesy
Earth motions, relationship in solar system, plate tectonics, and gravity
knowledge sources in geodesy
specialized application of several familiar facets of basic mathematics
- measurements/survey/expeditions
- modern technologies
key terms in geodesy
- datum (circle to sphere, ellipse to ellipsoid / spheroid, geoid)
- coordinates system
- projections
basic geometry for geodesy
- ellipse -> ellipsoid –> sphere
- 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.
how is the flattening f derived
f = (a-b) / a
- flattening is a small value, so usually the quantity 1/f is used instead
- flattening ranges from 0 to 1. a flattening value of 0 means the two axes are equal, resulting in a sphere.
what is datum
a reference point, surface, or axis on an object against which measurements are made
geodetic datum
a reference from which spatial measurements are made
spheroid of geodetic reference
-a spheroid or ellipsoid approx. the shape of the earth, a datum defines the position of the spheroid relative tot he center of the earth
older ellipsoids
are named for the individual who derives them and the year of development is given
international ellipsoid
developed by Hayford in 1910 and adopted by the international Union of Geodesy and Geophysics
a unified geodetic system for the whole world became essential bcuz
- advancement of space science and astronautics
- lack if inter-continental geodetic information
- need for global maps for navigation, aviation and geography and basis for a worldwide geo-data
what adopted the GRS80
international association of Geodesy (IAG) in 1979
what does a datum define
how a coordinate system is seated over the ellipsoid / spheroid
what is the centre mass of the earth
NAD83 system and uses the GRS80 ellipse
what is a geoid
a hypothetical earth surface representing the mean sea level in the absence of winds, current, and most tides
- the arithmetic mean of hourly water elevations observations over a specific 19-year cycle and defined as the zero elevation for a local area
- geodesists once believed that the sea was in balance with the earth gravity and formed a perfectly regular figure
earths actual gravity field
the earths gravity field differs from the gravity field of a uniform, featureless earth surface
ex. Zero elevation as defined by Spain is not the same zero elevation defined by Canada, which is why locally defined vertical Datums differ from each other.
can a geoid surface be directly observed
no heights above or below the geoid surface can’t be directly measured
how are geoid measured
inferred by making gravity measurements and modeling the surface
-Geoid is the equipotential surface of the Earth’s gravity field which best fits, in a least squares sense, global mean sea level- NASA
Geoid – Ellipsoid Relationships
The angle between a plumb line (perpendicular to the geoid) and the Normal line (the perpendicular to the ellipsoid) is called as the “deflection of the vertical”
new Canadian geodetic vertical datum
The Canadian Geodetic Vertical Datum of 2013 (CGVD2013) was officially released in November 2013 representing by convention the coastal mean sea level for North America.
It replaces the Canadian Geodetic Vertical Datum of 1928 (CGVD28).
what is CGVD28
a tidal Datum defined by the mean water level at five tide gauges: Yarmouth and Halifax on the Atlantic Ocean, Pointe-au-Père on the St-Lawrence River, and Vancouver and Prince-Rupert on the Pacific Ocean.
horizontal datum
used for describing a point on the earth’s surface, in latitude and longitude or another coordinate system.
vertical datum
used to measure elevations or depths.
-These are either based on sea levels or geoid and use the same ellipsoid models of the earth used for computing horizontal Datum
geometric datum
records both of above and the UTC (coordinated universal time)
what will a change in datum cause
a shift in every position the map
adjoining sheets may be in different Datum causing
a loss or addition of detail at the map’s neat-line
when using topo maps with adjoining sheets or with a GPS receiver you should always check..
the datum note first
