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24 Cards in this Set
- Front
- Back
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What is georeferencing?
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- unique information linking you to exactly one location
- ex. postal code |
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What are the three types of georefereneces?
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1. Metric - distance from a certain location
2. Ordering - for example, street addresses order houses along streets 3. Nominal - for example place names that do not involve ordering or measuring |
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What are the first three characters in a postal code called?
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FSAs - Forward Sortation Areas
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What is linear referencing?
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- a system for georeferencing positions along a road, etc
- combine name with an offset distance from a fixed point |
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What are cadasters?
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- maps of land ownership showing property boundaries
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What is geodesy?
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- the shape of the earth and definition of earth datums
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What are earth datums?
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- a datum is a set of reference points on the Earth's surface against which position measurements are made
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What is map projection?
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- the transformation of a curved earth to a flat map
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What are three types of Coordinate Systems?
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1. Global Cartesian coordinates (x, y, z) for the whole earth where x and y are for the equator and z shows the Greenwich Meridian
2. Geographic Coordinates (phi, lamda, z) where phi is latitude and lamda is longitude and z is elevation 3. Projected Coordinates (x, y, z) on a local area of the earth's surface In 1 and 2 the z is defined geometrically and in 2 it is defined gravitationally |
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What is a geoid?
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- a surface of constant gravitational potential, coincides with mean ocean surface of the Earth
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What are meridians?
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Lines of longitude
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What are parallels?
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Lines of latitude
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What is DMS and DD?
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DMS - Degrees-Minutes-Seconds
DD - Decimal degrees |
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What shape is the earth?
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spheroid - slightly larger in radius at the equator than the poles
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What is the earth datum defined by?
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- an ellipse and an axis of rotation
ex. NAD27 (North American Datum of 1927) uses an ellipsoid on a non-geocentric axis of rotation, while NAD83 uses one on a geocentric axis of rotation |
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What is the definition of latitude (phi)?
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- angle away from the equatorial plane
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What is the definition of longitude (lamda)?
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- angular distance of a place east or west of the prime meridian
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What is a gravity anomaly?
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- elevation difference between a standard shape of the earth and a surface of constant gravitational potential (geoid)
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What is elevation measured by?
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- by the geoid (as a vertical datum - z)
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What are the two types of projections to prevent distortions?
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1. Conformal Property - shapes of small features are preserved, anywhere on the projection the distortion is the same in all directions
2. Equal area property - shapes are distorted but features have correct area - both types distort distances |
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What are the three types of projections?
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1. Conic
- good for East-West land areas - like wrapping a cone of paper around the Earth - lines of latitude appear as arcs of circles and lines of longitude are straight lines radiating from the North Pole 2. Cylindrical - good for North-South land areas (ex. Transverse Mercator) - wrapping a cylinder around the earth 3. Azimuthal - good for global views - want to pick one with tangent closes to area of study |
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What is high co-variance?
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- when 2 variables (ex. soil texture and conductivity) are very related
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What is the definition of map scale?
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- ration between distances on a map and their actual ground distances
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What are the three types of scale?
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1. Graphic - scale bar
2. Statement of scale - verbal expression, ex. one centimetre on the map represent one kilometre on the ground 3. Representative Fraction (RF) - written as ratio map distance : ground distance |
