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46 Cards in this Set
- Front
- Back
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What are some concerns with GIS? |
Ethics |
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the 5 M's of GIS application |
Mapping Measurement Monitoring Modeling Management |
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Concept of representation: |
construction of a digital model of some aspect of the earths surface |
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What are the choices of representation that have to be made? |
level of detail, generalization remove detail in order to reduce data volume |
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Toblers law of geography |
everything is related to everything else, but near things are more related than distant things |
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GIS geographic attributs classified: |
Nominal: distinguishes one entity from another (tree, grass)
Ordinal: values have a natural order (rating scheme from 1=good to 3=bad)
Ratio: ratio between value make sense (100k twice as heavy as 50kg)
Cyclic: data beyond four (direct of flow or aspect) |
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discrete objects: |
polygons (buildings), lines (roads), points (bears) |
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Continuous fields: |
Changes in value across a surface where the world is the surface
Distinguishes by what varies and how smoothly
elevation |
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GIS Raster, and Vector |
Two basic methods for representing geographic data in digital form:
Raster: space divided into an array of rectangular (usually square) cells
Vector: a series of points which may be connected to represent a line or polygon |
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for GIS vector there are Topology |
Topology- A set of rules that describe which define the relationship between points, lines, and polygons |
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Nature of spatial variation:
Proximity: |
effects are key to representing and understanding spatial variation |
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What is spatial auto correlation |
The degree to which a set of features tend to be clustered together (positive spatial autocorrelation) or be evenly dispersed (negative spatial auto correlation) over the earths surface |
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Sampling |
how you survey a region or subsequently sample an area may be influenced by geographic space |
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Distance effects |
as distance increases the relationship may be different and is dependent on the attribute of interest |
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What is ESSENTIAL to GIS? |
Location |
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What is required to place different pieces of information together? |
tie information together in space, and used to measure distances and areas |
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What is unique about georeference? |
there is only one location associated with a give geo reference, no confusion |
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Who is georeference meant to be shared with |
all people who wish to work with the information |
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what mus georeference be inorder to be useful? |
must be persistent through time |
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What are georeferences called when they are not based on name? |
metric georeferences because they are based on measurements |
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metric georeferences are essential to? |
making maps, display of mapped information, and any kind of numerical analysis |
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Cadasters |
is defined as the map of land ownership in an area
US public land survey system |
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What is the major axis perpendicular to the earths center of mass? |
equator |
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What is the minor axis around which the earth rotates? |
Prime meridian |
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Longitude |
is measured in 180 degrees west or east of the prime meridian |
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Latitude |
is measure 90 degrees north or south of the equator |
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What is earths shape? |
geoid, or spheroid, or ellipsoid |
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Why do we display the earth as a flat object? |
Many technologies working with geographic data are inherently flat |
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Projections |
Defined by how you place the earths surface on a flat peice of paper |
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projections:
GIS is a powerful tool for: |
converting between projections and coordinate systems |
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Methods for converting: |
Convert list of customer addresses to coordinates for mapping and analysis (geocoding)
Combining datasets that use different systems of georeferencing
converting projections
Positioning a GIS map by centering on places of interest |
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Georegistration |
just defining the coordinate system |
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Georectify |
take an image not adjusted to be in a known coordinate system and put it into a known coordinate system |
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Cartography/ Map production |
cartography is concerned with art, science, and techniques of making maps or charts
Maps can be both paper and digital forms
The actual presentation of the map is dependent on the form desired and its use
maps are both storage and coomunication mechanisms |
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What are the drawbacks of cartography and map production |
Maps can be used to miscommunicate information either accidentally or on purpose
maps are a single realization of a spatial process
Maps are often created using complex rules, symbology, and conventions and can be difficult to understand and interpret by the untrained viewer |
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Seven controls on the map design process |
purpose- determines what is mapped
reality- phenomena being mapped provides some contrasts
available data- charectaristics of data will affect the design
map scale- control the quality of the map
audience- controls type of data displayed and how
conditions of use- environment of use determines what is presented
technical limits- display medium, hard copy or digital |
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Map key elements: |
map body inset/overview map title legend scale direction indicator map metadata (source) |
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Why is symbology important? |
it is important in what you are trying to convey |
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What is the 3 tier architecture? |
User interface
Tools
Data management
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Why code? |
allows for batch processing in loops - you have 1,000 files that need the same type of analysis done on them
Retain the methedology so it can be repeated
model logic may be followed later to allow for a repeat process with similar data/information |
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GIS program in 25,000 dollars so |
this is why some people build their own GIS system |
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Raster data capture |
Most popular form of remote sensing - active and passive sensors
Resolution is the key from a IS perspective -spatial -spectral -temporal
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Heads up digitizing |
defining a point, line and polygon objects on- screen using point or stream digitizing |
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digitizing errors |
overshoots undershoots gangling segments silver polygons tolerance levels can close off polygons misalignments |
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Geographic DBMS extensions |
data storage, retrieval, and management |
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What does indexing quicken? |
the run time for some operations |
