1. GIS Analysis Queries Operations Non-spatial Spatial Vector Raster
what is the population of this city?
show me the roads longer than 1km
(population and road length must be recorded in the attribute table)
Spatial
where is the closest bus stop? (proximity)
in what region is this city? (containment)
what are the neighbours of Italy? (adjacency)
which regions are crossed by this river? (intersection)
and many others
Operations
Vector
Raster
Mixed

2. Non-spatial queries
All countries whose population is more than 30,000,000

3. Spatial queries Containment Query
Given a spatial object, find all objects that completely contain it
Which country surrounds Lesotho?
If the object is a point, this is called a Point Query
Where is Khartoum?

4. Spatial queries Region Query
Given a polygon, find all objects in the map that intersect it.
When the polygon is a rectangle, the query is called Window Query
Enclosure Query
Given a polygon, find all objects that are completely contained in it.
Which countries are completely contained by South Africa?

5. Spatial queries Intersection query
Given a polyline, extract all objects in the map that interect it.
Which countries are crossed by the Nile and its tributaries?

6. Spatial queries Range query
Given an object, extract all objects that are within a given distance from it
Which African capitals lies within 1,000 km from Ouagadougou?
Nearest Neighbour Query
Given an object, find the object in the map that is closest to it.
K-Nearest Neighbour Query: find the k nearest objects

7. Spatial operations - vector
Clipping (intersection)
Given a polygon, extract all portions of objects in the map that are contained in it.
The geometry of the objects in the result corresponds to the intersection of the object with the window, i.e. they are modified.

8. Spatial operations - vector
Merge (Dissolve)
Given two (or more) objects, return their geometric union
Show the political situation of Horn of Africa 30 years ago

9. Spatial operations - vector
Buffering
Given an object, define the area(s) that lie within a given distance(s) from it
Areas that are within 100 km from the Nile and its main tributaries
Difference (symmetric difference)
Given two layer, logically subtract one from the other

10. Spatial operations - vector
Intersection (AND) Union (OR)

11. Spatial operations - vector
Union
Intersection
Difference

12. Spatial operations - raster
The raster data model performs overlay operations more efficiently than the vector model.

13. Spatial operations - raster
Local operations
Example of a raster query
(Elevation > 1000m) AND (Slope > 50%)
Map Algebra (create a new layer)
(MeanTemp2010 – MeanTemp2000) = TempChange

14. Pay attention to data format problem:
Spatial operations - raster
Pay attention to data format
problem:
calculations with integers yield integers
(4 / 3) x 3 = 3
solution:
convert the data format before performing calculations
(float (4) / 3) x 3 = 4

15. Spatial operations - raster
Focal operations
Examples:
Slope and aspect calculations on a DEM
Filtering

16. Spatial operations - raster
Zonal operations
Example: zonal mean
zones values

17. Spatial operations - raster
Global operations
Example: reclassify

18. Spatial analysis - raster and vector
Interpolation
inverse distance weighting (arithmetical)
spline interpolation (mathematical)
kriging (statistical)
use of barriers