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44 Cards in this Set
- Front
- Back
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UTM
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Universal transverse Mercator grid system. Total 60 zones numbered with zone one beginning at 180'w. each zone covers 6 degrees of longitude and further is divided into the northern and Southern Hemispheres.
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Scale factor
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ratio of local scale to principal scale
ideal scale factor = 1 UTM scale factor along central meridian = 0.9996 |
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Standard line
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Tangent line between projection surface and the reference globe; there is no distortion along this line
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Central line
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Defines the center of map projection
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UTM False Northing
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10 million m South of equator
on the equator |
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UTM False Easting
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500,000 m West of central meridian
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Geographic Coordinate System GCS
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A reference system that uses latitude and longitude to define the locations of points on the surface of a sphere or spheroid. A geographic coordinate system definition includes a datum, prime meridian, and angular unit.
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Datum
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The reference specifications of a measurement system, usually a system of coordinate positions on a surface (a horizontal datum) or heights above or below a surface (a vertical datum).
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Geodetic datum
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A datum that is the basis for calculating positions on the earth's surface or heights above or below the earth's surface.
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Topology
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Study of those properties of geometric objects that remain invariant under certain transformations such as bending or stretching.
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Georelational data model
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A geographic data model that represents geographic features as an interrelated set of spatial and attribute data. The georelational model is the fundamental data model used in coverages. (compare: Object-based data model for geodatabases)
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Query
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A request to select features or records from a database. A query is often written as a statement or logical expression.
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Orthophoto
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An aerial photograph from which distortions owing to camera tilt and ground relief have been removed. An orthophotograph has the same scale throughout and can be used as a map.
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Ground control point
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One of various locations on a paper or digital map that has known coordinates and is used to transform another dataset—spatially coincident but in a different coordinate system—into the coordinate system of the control point. Control points are used in digitizing data from paper maps, in georeferencing both raster and vector data, and in performing spatial adjustment operations such as rubber sheeting.
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Geometric transformation
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The process of rectifying a raster dataset to map coordinates or converting a raster dataset from one coordinate system to another.
Done through first order (affine) transformation or higher order, then resampling. |
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RMSE
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A measure of the difference between locations that are known and locations that have been interpolated or digitized. RMS error is derived by squaring the differences between known and unknown points, adding those together, dividing that by the number of test points, and then taking the square root of that result.
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Resampling
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The process of interpolating new cell values when transforming rasters to a new coordinate space or cell size. Done by: nearest neighbour, bilinear interpolation, cubic convolution
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Relational Database
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A data structure in which collections of tables are logically associated with each other by shared fields.
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Relational Data Model
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Tuple + Relation + Key
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Tuple
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A row or record in a database table; set of facts (datum) that are related to each other.
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Datum
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Each fact in a tuple (row) whose value comes from a specified domain (field/column header).
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Relation
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Set of tuples over all domains of a table, or a subset of all tuples over domains of a table.
**Must not have duplicate tuples therefore cannot be the same as a table. Each tuple in a relation can be distinguished by their values of attributes. |
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Key
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Any set of attributes whose values necessarily uniquely identify a tuple.
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Normalisation
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Process of decomposition by taking a table with all of the attribute data and breaking it down into small tables WHILE MAINTAINING THE NECESSARY LINKS BETWEEN THEM.
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Table Join
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1:1 or M:1 relationship
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Table Relate
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M:N
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Types of Relational Databases
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Hierarchical database, Network database, Relational database
Benefits - tables are separate until a query or operation is run hence less data and time is needed for processing; each table can be edited separately and changes are updated automatically across tables |
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Data Error Types
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Locational Error - fix by checking with source maps
Attribute Error - bank/bank/bank, typos, fix by checking manually or audit Topological Error - fix by map manipulation tools to edit features *Non-topological editing is done on the data without there being a topological error |
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Topology Rule
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Stored in a geodatabase as one or more relations between features within one feature class or between more than one feature class. One topology rule can contain each feature class once.
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Topology in Geodatabase
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Cluster tolerance + Feature classes participating in it + Dataset + Topology rule
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Buffer
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A polygon enclosing a point, line, or polygon at a specified distance. Creates zone of interest around an entity. Is done through spatial analysis or as an editing tool (proximity selection).
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Overlay
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Combination of two or more map layers within a GIS to create one or more map layers with combined attributes from the original data.
CHANGE IN GEOMETRY, ATTRIBUTE, TOPOLOGY. Functions: Union, Intersect, Symmetric Difference, Identity |
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Identity
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(input) AND (identity) OR (input)
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Function of Overlay:
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Sliver polygons error detection from high precision of GIS digitisation
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Map Manipulation Tools
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Done between data entities on the same layer. Product is not on a new layer, and retains the original data attributes individually. Geometry is changed.
Unary: Dissolve, Append, Eliminate, Select, Split Binary: Clip, Erase, Update |
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Interpolation
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Procedure of estimating value at unsampled sites within an area covered by existing observations.
Areal interpolation transfers known data from one set of source polygons to target polygons. |
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Binary model
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Uses logical expressions to select target areas fro ma composite feature layer or multiple rasters. Output in binary format 1 & 0
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Data analysis environment
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Area for analysis (analysis mask)
Output cell size (resolution is lower of the two inputs) |
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Map Algebra
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A language that defines a syntax for combining map themes by applying mathematical operations and analytical functions to create new map themes.
For raster: consists of OBJECTS, ACTIONS (Functions + Operators) |
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Map Algebra Operators
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Boolean operators, arithmetic operators (/ + - MOD), relational operators (logic < >)
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Map Algebra Classification
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Local
Focal Zonal Global |
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Local Raster Map Algebra
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Data type conversion: floating to integer, % to degree
Reclassification: one-to-one change in value or range-to-one value change Overlay with multiple rasters Combine: unique value to each combo of input values |
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Fonal Raster Map Algebra
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1. Choosing neighbourhood: rectangle, annulus, wedge, circle
2. Moving window to fill up all the focal cells: mean, majority, max, min, median, range, std dev, sum, variety 3. Applications: Generalisation (Ave), Edge enhancement (Range), Edge smoothing (Majority) |
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Zonal Raster Map Algebra
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All output cells within the same zone have the same value.
Functions: - Statistical (mean) - Geometric (Area, perimeter, thickness, centroid) **Euclidean Distance and shortest distance (bearing/angle, distance), buffer distance |
