GIS/GPS Chapter 6

Databases

heat of GIS b/c they make spatial data query possible based on attributes, DBMS used to add/edit/query/analyze and report on attribute and is sum of attributes and spatial object, computer-aided design (CAD) programs don’t have this ability

Flat files

single file, columns is field, row is individual record, good for small data sets

Relational databases

primary key related to foreign key and common key, allows users to link 2+ databases/tables together

Primary key

related to one another by unique identifers

Foreign key

same field in adjoining databases

Common key

if primary key has same field name as foreign key

Different database relationships

database 1 has responding record in the second database, one to many with applying to records and vis a versa with mathematical operators/records, many to many with applying to many relationships

Relate

temporarity connects tables based on common key but table is physically separate

Join

combine 2 tables with a common key and used in 1 to 1 and many to 1 relationships

Raster databases

attribute table only for rasters with type integers, count of number of pixels

Type of attribute data

nominal, ordinal, interval, ratio

Can all attributes be queried?

no, BLOB cannot (binary large object/image)

Statistics for nominal

mode

Statistics for Ordinal

mode and median

Statistics for interval and ratio

mode, median, mean, SD, and variance

What does it mean if the median and average are the same?

distribution is normal

Adding and deleting attribute fields

consider field type and restrictions on edits/calculations a field type presents w/ not assigning a flow type, delete entire field if they are useless/redundant or hide them

What does assigning a flow type do?

takes up more storage

Data entry

manually by hand, calculate command, python/VBA (visual basic, coding excel) script

Data query with select by attribute

SQL query statements can also contain Boolean connectors

Data query with select by location

can select by location, select features from NHD Flowline with lines representing streams in a location, input source layer with lakes/oceans

Multiple fields

input for more layers