1. BASIC SPATIAL ANALYSIS TOOLS IN A GIS
database queries
basic statistics
buffering
overlay
reclassification

2. GIS ANALYSIS TOOLS

3. GIS ANALYSIS TOOLS
Database tools: query and summarize (similar to spreadsheet or database program
contains spatial component
Grid-based: buffering, overlay and map calculator tools
Image processing and terrain analysis: based on moving window that create new maps from patterns on the original

4. QUERIES Ask questions about GIS databases: Where are the older stands?
Which roads are paved?
Which trails are authorized?
Which water sources are within a certain distance of a road?

5. QUERIES Where are the thinnable stands?
Age  30 and Age  Age  30 and Age  40 and MBF  30

6. QUERIES Structured Query Language (SQL) uses standard operators
e.g. = > < *
“and” “or” “not”
standard order of operations
add/subtract before multiply/divide
use parentheses to “isolate” terms

7. QUERIES
Example:
select stands greater than 30 acres with grass understories and a mean quadratic diameter less than 20 inches.
query for above:
(area > 30) and (understory = “grass”) and (QMD < 20)

8. QUERIES Which water sources are within a certain distance of a road?
we need more information.
perhaps a new database layer.
“buffering” may help answer this question

9. BASIC STATISTICS
statistics can help determine meaning within the data
simple, sum, count, mean, maximum, range, variance and standard deviation
calculates statistics for a combination of fields, for example:
by combining the ‘State’ name field & ‘Population’ fields, we can calculate the average state population

10. BUFFERING
defining closed areas (polygons) within a certain distance of selected landscape features:
to identify areas surrounding geographic features
identify / select features that then fall within / outside the boundary of the buffer
provide summary measures of proximity

11. BUFFERING
you can buffer points, lines and polygons

12. BUFFERING What do the riparian buffer zones look like?
How far around an owl nest location is 70 acres?
What do the visually sensitive areas around trails encompass?

13. BUFFERING
problems may occur when buffering very convoluted lines or areas; or for large datasets
may have to increase the virtual memory of your system
or break the job up into a number of smaller pieces

14. BUFFERING Site selection
determine location of new well – make sure it does not fall within 10km of chemical factories
find all stream segments within 300 feet of a proposed logging area

15. BUFFERING Environmental pollution
zone of noise pollution around major roads
buffers around contaminated land to prioritise sites (according to land use, water courses & ground water protection zones)

16. BUFFERING Resource management / Planning
service zones (e.g. 2,000 m around recycling centres)
create protection zones around features (e.g. nature reserves)
e.g. Bus routes

17. BUFFERING Epidemiology
disease clusters around certain features (e.g. asthma surrounding incinerators)
Crime
to examine if car crime is more prominent in certain areas (e.g. close to major roads, street corners, car parks)

18. OVERLAY processes involving two (or more) layers
merging is a simple overlay process that combines two or more layers into one. It leaves overlapping regions and does not create new attributed polygons where there is overlap.
three overlay processes are considered here:
Union
Intersect
Identity
in contrast to a simple merge, each of these operations will produce a new layer with unique combinations of the input database polygons.

19. OVERLAY
Laying one GIS database on another to produce a combination of the two.
Union:
determining the combination of two GIS databases.
resulting GIS database will extend as far as both input
GIS databases extend

20. OVERLAY
Union: What is the combination of the stands and the fire area?
Input GIS
database #1
database #2
Output GIS
database

21. OVERLAY

22. OVERLAY
Laying one GIS database on another to produce a combination of the two
Intersect:
finding the overlapping areas between two GIS databases

23. OVERLAY Intersect: Where do the stands and the fire area overlap?
Input GIS
database #1
database #2
Output GIS
database

24. OVERLAY
Laying one GIS database on another to produce a combination of the two.
Identity:
determining how one GIS database can be modified by the position of features in another.
limited to the spatial extent of the first GIS database.

25. OVERLAY Identity: Where does the fire occur in the stands database?
Input GIS
database #1
database #2
Output GIS
database

26. BOOLEAN OPERATORS Definitions to retrieve geographical data
essential part of most GIS projects
Usages
to check the quality of data and the results obtained (i.e. hotels in the sea after digitising or data conversion)
Boolean operators
A AND B, A OR B, A NOT B, A XOR B, (A AND B) OR C, A AND (B OR C)

27. BOOLEAN OPERATORS 1 = ‘true’ 0 = ‘false’
A B NOT A A AND B A OR B A XOR B

28. BOOLEAN OPERATORS
Venn diagrams

29. BOOLEAN OPERATORS

30. OVERLAY TYPES - VECTOR Point in Polygon
overlay point objects on areas, compute "is contained in" relationship
points a,b,c...n, are contained within polygon x
result is a new attribute for each point in the database

33. OVERLAY TYPES - VECTOR Line on Polygon
overlay line objects on area objects
compute "is contained in" relationship
lines are broken at each area object boundary
containing area is new attribute of each output line

37. OVERLAY TYPES - VECTOR Polygon on Polygon
overlay two layers of area objects
boundaries are broken at each intersection
number of output areas likely to be greater than the total number of input areas
after overlay we can recreate either of the input layers by dissolving and merging based on the attributes contributed by the input layer

38. OVERLAY TYPES - VECTOR

39. OVERLAY TYPES - RASTER very fast and easy compared to vector overlay
extent of calculations is much less
cell-by-cell basic
new cells are assigned attributes composed from original cells
condition: both layers have identical geometry
quantitative or qualitative overlay
less flexibility with attributes

40. OVERLAY TYPES - RASTER
raster maps treated as arrays of numbers to be added, subtracted, etc.

41. OVERLAY TYPES - RASTER High slope (red) + Private land (blue) =
Potential areas for a ski resort (brown)

42. OVERLAY TYPES - RASTER Map Algebra operators
arithmetic operators: +, -, *, /, ^,
grid2 = grid0 + grid1
logical operators, =, >, <, >=, <=, <>, etc.
grid2 = grid0 > grid1 (grid2 becomes 1 where this is true, 0 where false)
mathematical functions (trigonometric, logorithms, etc.)
grid2 = sin(grid1)
best raster systems allow multiple input grids
grid5 = grid1 * ( grid2 + grid3 - grid4 )
Saves calculating and storing intermediate grids

43. RECLASSIFICATION input is result of classification
grouping of attributes according to limits with no change in geometry
results usually in a lower number of classes
aim:
to remove detail to emphasize spatial patterns
visualize new pattern and connections
transformation from one classification system to another (e.g. soil types to agricultural land use suitability)

44. RECLASSIFICATION Household Income 0 – 5000 5000 – 10,000
10,000 – 20,000
20,000 – 40,000
40,000 – 60,000
50,000 – 75,000
> 75,000
Low Income Group
Middle Income Group
High Income Group

45. RECLASSIFICATION
results usually in a lower number of classes

46. NETWORK ANALYSIS
movement or distribution of resources across a connected network or arcs.
routing
optimum path between two locations
allocating
maximize capacity at a facility
e.g. assign streets to fire stations
address Matching
locate street address along an arc based on address

47. SURFACE ANALYSIS three dimensional analysis (x,y,z)
lattice or TIN (Triangulated Irregular Network)
viewshed, profile, volume, slope, aspect
not always based on elevation
e.g. pollution, climate data, water table, etc…