Summary
Summary terms Advanced GIS for Geoscientists (GEO4-4433)
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This document exists of different terms used in the Advanced GIS for Geoscientists course and gives a definition for each term.
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GIS components Software, hardware, data, people, and methods.Vector Points and vertices are connected by arcs (lines) and then connected as polygons.
Analysis: selection, clip, overlay (on top of each other: identify, intersect, symmetrical difference,
union, and update) and buffer (=zone of interest by dissolve (continuous area) or Thiessen polygon
(interpolation method that assigns points to area). It is a specified distance of the original objects).
Vertex Corner point of a polygon or other geometrical shape.
Shapefile Vector with associated attributes. It is a formal containing a polygon or other
geometric features. Set of files. Always keep them together
Lattice Vector of raster image
TIN Triangular Irregular Networks: vector visualisation of continuous surfaces
Raster Stored values in cells with a coordinate system. Continuous data Whole numbers or
floating numbers. Analysis: feature to raster (cell size determines scale), map algebra, functions,
reclassify.
Integer (I) Whole numbers without decimal points
Floating point (F) decimals
Image Raster with continuous or discrete spatial data
Local function Single cell. Goniometric, exponential, logarithmic, reclass, select and statistics.
Focal function Calculates statistics for the centre and its surroundings and compares the cell to its
neighbours. Examples: max, min, mean, sum and stdv.
Zonal function Surround, determined by another layer. Max, min, mean, sum, stdv, range, perimeter.
Global function all cells present, value dependent all cells input grid.
Geometric analysis: Slope, Aspect, Hillshade
Slope Measure of steepness, it is the difference in elevation between a cell and its
neighbouring cells. Degrees (until 90 degrees, use right triangle with arctangent) or percentages
(infinity, = elevation difference/distance*100).
Aspect Measure of down-slope direction. It is calculated by comparing the elevation of a cell
to its neighbours. Aspect values are measured clockwise in degrees from – to 360. E.g., north is
337.5-22.5 degrees. -1 is when the surface is completely flat and has no slope.
Hillshade What a surface would look like when illuminated by a hypothetical light source. The
position of the light source uses Azimuth (=direction of light source) and Altitude (=angle of the light
source above the horizon).
Hydrological analysis: runoff, groundwater, darcy flow
Surface analysis: viewability, military, cost-distance
Boolean operations: and (A and B), or (A or B or both), not (A not B) and xor (A or B but not both).
Euclidean distance specifies barriers, maximum distance.
Geodatabase Data stored here.
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