spatial database structure Flashcards
database
structured set of data that has a connection or relationship to each other
database may contain both non-spatial and spatial data
GIS directly deals with spatial data
advantages of digital databases
multiple access methods
data sharing more efficient
redundancy and costs mininmizes
central control and maintenance
efficient analysis and production of info for decision mkaing
data relationships
draw pic slide 7
relational (tabular) db model
most common
data is stored in and relationships are created between one or more flat files or tables where each pair of tables has a field in common or key
data extracted using SQL
geodatabase model
container of db files
data model uses an object-relational arrangement of the data
2 parts: data types and database schema
types: feature classes, raster datasets and tables
db schema contains info about objects and their relationships
querying the db
attributes (non-spatial)
location (spatial)
graphics (geometry)
GIS data input sources
keyboard entry: entering values into tables/templates
manual digitizing: digitizing tablet
automatic digitizing: large format scanner
data transfer: data from GPS
maps present unique problems
deformation
generalization
artifical errors
quality and accuracy standards
data interoperability
data source 1: GPS
constellation of earth orbiting satellites maintained by the USA for the purpose of defining geographic positions on and above the surface of the earth
3 segments of GPS
space - satellite
control - base stations
user - gps receivers
challenges with gps recevier
selective availability
multipath errors
dilution or precision
selective avail
us dept of defense distort the satellite time signal reducing positional accuracies
multipath errors
signals coming directly from the satellite and reflected off other objects interfere and create location errors
dilution of precision
geometry of satellites in the horizon are not equally spread out but clustered
data source 2: canadian census
census table
census geog
data source 3: open data
avail on web
data interoperability
deals with seamless interactions b/w people, data and systems
goal is to share, preserve and manage data, info and knowledge
metadata is needed to
identify geospatial resources
exchange
manipulate
catalouge
stylesheets
used to format the metadata
determine the layout and other style info aboht the data
documenting data quality
location accuracy and precision
attribute accuracy and precision
logical consistency
completeness
data currency
accessibility
