GEOG363 EXAM 2 Flashcards
majority of cost and time in building a GIS
data preparation/building the database
on screen digitizing
“heads up” with vectors
what will happen to digitizing errors as you increase the scale of the map
the error will increase proportionate to the increase in map scale
little errors in the large scale can mean huge scales in small scale maps
name 5 types of positional errors
- undershooting/overshooting nodes
- open polygons
- missing nodes
- self intersecting lines
- sliver polygons
what does snap tolerance do?
it snaps undershot nodes to lines through buffers
what to options do we have to correct positional error
- redraw
2. choose master boundary
registration
when layers spatially coincide
name 2 examples of post-processes
- smoothing
2. spline - interpolates curves to reduce jaggedness of edges
name 3 sources of rasters
- scanned maps
- remote sensing
- statistical surfaces
what is the difference between an image and a photograph
photographs are specific to images that are on film
unreferenced raster refers to…
when coordinate values to position an image are missing
regular raster distortion (3)
image is out of:
- scale
- shift
- rotation
irregular raster distortion (2)
- terrain
2. flight conditions
what do we call fixing regular and irregular raster distortion
orthoimagery
affine transformation
preserving the parallel nature of lines and ratio of distances
collinear
any number of points can be said to be collinear if a straight line can pass through them all
3 types of affine transformation and define them
- translation (sliding)
- rotation
- dilation (scaling)
what kind of distortions are affine transformations good for?
regular
what kind of distortions are higher order polynomials good for?
irregular
RMSE
root mean square error
a measure of precision between true and computed coordinates of points
NOT ACCURACY
nearest neighbor
assigns output cell value from nearest corresponding input cell
bilinear interpolation
uses nearest cell and next closest 3 to get a weighted average
what does georeferencing develop in order to transform all cells of a raster
equations
difference between a database and DBMS
DBMS allows access and understanding of data
name 5 things DBMS can offer that databases cannot
- locking
- rights
- views
- back ups
- monitoring
what does n-tier architecture describe
allows users (web users [upper tirer]) to access data (in a database [bottom tier]) to interpret data without accessing the data itself
how can multiple tables be joined?
through a common unique ID attribute
what kind of algebra is used in query language?
relational algebra
name and define 4 different hings that can be done with relational algebra
- intersect - in both tables
- union - add two tables
- difference - take away from one table
- join - link tables through a key attribute
SQL and define
Structured Query Language is a special programming language used to manage data in a RDBMS
Primary key
one column that contains a unique value for every row in the table
what is something primary keys can be used for
cross referencing two different tables - here it acts as a foreign key
3 rules of tables
- cannot be 2 identical rows
- there must be a primary key
- the primary key may not contain any null values
functional dependency
an attribute is functionally dependent if it is determined by the value of another attribute
local spatial operations
one input for one output
neighborhood spatial operations
local and nearby input influence output
global spatial operations
entire input layer is used to determine each local output
dissolve operation
features with same attribute value are merged
creation of aggregated polygons
2 most important tools of GIS analysis
buffers and overlays
how were overlays done back in the day
with transparent copies
father of GIS
Dr. Roger Tomlinson
overlays combine data to do what two things?
join attributes or filter out data
what 3 things must be done before working with overlays?
- georegistered
- same resolution
- functionally related
what will overlays that combine different vector geometries result in?
a layer with a lower dimensional geometry
what are network structures used for?
to represent features such as roads, pipelines, rivers, etc
name 2 things network analysis can be used for
route selection
resource allocation
geocoding and its problem
linear referencing of addresses along road features
NOT ALL BUILDINGS ARE OF EQUAL SIZE OR SHAPE
gazetteers
place name directories that contain spatial information and feature type
pizza shop is here
ontology
classification of feature types
what does reclassification do to new values
makes the resulting class more generalized
MAUP and define
Modifiable Areal Unit Problem
Changing the size or shape of an object can alter the values in the classes
natural break classes
minimize intraclass differences and maximize interclass differences
spectral signature and example
certain things in a remote senses photograph have a specific color
EG water is blue
georectification
adding control points to photos to make them accurate
transit costs
weight used to make models that use attribute data to weigh distances
equal area
take x classes and make sure that they have the same area
what do thematic maps emphasize?
attributes
often only one or a few
what do reference maps emphasize
features
often many features
ecological fallacy
to assume that a generalized statistic refers to an individual within a population
name 3 types of vector buffera
simple
compound
nested
