Data exploration: Exploration, attribute data query, spatial data query, raster data query, geographic visualization

1. GEOGRAPHICAL
INFORMATION
SYSTEM
UNIT 4
WE-IT TUTORIALS (PH:8097071144/55)

2. 'Data Exploration' with its
various aspects
 data exploration in GIS lets the user view the general patterns in the
data set, query data subsets, and hypothesize about possible
relationships between data sets
 data exploration in a GIS involves both spatial and attribute data
 media for data exploration in GIS include maps and map features
WE-IT TUTORIALS (PH:8097071144/55)

3. Different types of graphs are
used for data exploration
 A line graph
 A histogram (bar chart)
 A cumulative distribution graph
 A scatterplot plotting
 A bubble plot
WE-IT TUTORIALS (PH:8097071144/55)

4. 'Attribute Data Query' with its
various aspects
 Attribute data query retrieves a data subset by working
with attribute data
 The selected data subset can be simultaneously
examined in the table, displayed in charts, and linked to
the highlighted features in the map
 SQL (Structured Query Language)
 Query Expressions (where ph=1.4)
 Type of Operation(set subset “and or”)
WE-IT TUTORIALS (PH:8097071144/55)

5. how an attribute query is executed on
a relational GIS database
 Query, joins, and relationship
WE-IT TUTORIALS (PH:8097071144/55)

6. 'Spatial Data Query' with all its
aspects
 Spatial data query refers to the process of
retrieving a data subset from a layer by
working directly with features.
WE-IT TUTORIALS (PH:8097071144/55)

7. Spatial relationships used for
query includes
 Containment(finding schools within a
selected county)
 Intersect(selecting land parcels that intersect
a proposed road)
 Proximity(finding state parks within 10 miles
of an interstate highway)
WE-IT TUTORIALS (PH:8097071144/55)

8. Combining Attribute and
Spatial Data Queries
 Locate all gas stations in the study area, and select
those stations with annual revenues exceeding $2
million through attribute data query. Next, use spatial
data query to narrow the selection of gas stations to
those within 1 mile of a freeway exit.
WE-IT TUTORIALS (PH:8097071144/55)

9. 'Raster Data Query' with all its
aspects
 Query by Cell Value
 The cell value in a raster typically represents a
specific attribute value (e.g.. land-use type,
elevation value, etc.) at the cell location.
WE-IT TUTORIALS (PH:8097071144/55)

10. Geographic Visualization and
its various techniques
 Data Classification (explore rates of
unemployment by state in the United States)
 Spatial Aggregation(Spatial aggregation is
functionally similar to data classification
except that it groups data spatially)
 Map Comparison(Map comparison can help
a GIS user sort out the relationship between
different maps. )
WE-IT TUTORIALS (PH:8097071144/55)

11. END OF UNIT 4
WE-IT TUTORIALS (PH:8097071144/55)