gis analysis. questions to answer position – what is here? condition – where are …? trends –...
TRANSCRIPT
GIS Analysis
Questions to answerQuestions to answer
•Position – what is here?
•Condition – where are …?
•Trends – what has changed?
•Pattern – what spatial patterns exist?
•Modeling – what happens if ...?
Tools to answer the questions I.Tools to answer the questions I.
•Selection
•Based on database tables (Where are …?)
•Spatial conditions (What is here?)
SQL queries
Clicking at a point
Inside a circle
Inside a box
Inside a polygon
Contains entire, contains partly, contains the centroid
•Spatial join of two layers
•Buffers
Near of far from spatial objects
Constant buffer distance
Buffer distance from an attribute
Multiple buffers
Tools to answer the questions II.Tools to answer the questions II.
Tools to answer the questions III.Tools to answer the questions III.
•Overlay analysis (two layers, one of them contains polygons
UnionIntersection
•Other operations
Cut
Paste
dissolve
Sliver polygons
Analysis sample
10 km buffer
Waters Soils Sunshine
Soil = 8 and sunshine > 1800
All conditions are fulfilled
intersection
intersection
Results of analysisResults of analysis
Analysis on raster I.
Grids with the same resolution and extent
Operations among cell at the same position
Grid algebra
„No data” value, involving any operation the result is„No data”
Arithmetic operators +, -, *, /
Functions
Raster analysis II.
Resampling
Nearest neighborhood
Bilinear interpolation (2x2)
Bicubic interpolation (4x4)
Fuzzy mathematics (Zadeh 1965)Handling spatial uncertainty
Instead of 0/1 (yes/no) values many categories or continuous value,It fits better to the human logic
Subjective information can be considered
Membership function: (l) [0,1]
Set operations: Complement l L : 3(l) = 1 - 1(l)
Union l L : 3(l) = max{1(l) , 2(l)}
Intersection l L : 3(l) = min{1(l) , 2(l)}
It can be solved for raster data simplyFuzzy module available in Idrisi
Finding routesUtility network models (road network, sewers, etc.)
Directed weighted graph
Edges
Nodes
Impedances
Topology
Optimal route (shortest path)
Optimal route between two nodes (minimal weight sum)
Dijkstra algorithm 1959
Other restrictions, one-way edges, turning impedances
Finding addresses
2
1
24
17
Apple str.Road network, street name,house numbers from and to
Apple str 5thLinear interpolation
Difficulties: house number like 2-4, 8/a, squares
For example criminal statistics
Finding road intersections
Address nodes
x, y coordinates for each address
Joining databases to the map
Nodes are the midpoint of pixels
4/8 directions
Impedance function
Application:Watershed boundary
Flow directions
Flow accumulation
Optimal route on raster