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