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| GIS: Methods of analysis / GIS TRAINING |
CHAPTER4: Methods of analysis in a GIS
Queries and interrogations
- Query, exploration, statistics
Metric measurements and calculations
- Metric properties of objects: length or perimeter, surface, etc.
- Relationships between objects: distance, orientation
Data transformation
- Creating new descriptive attributes
- Based on arithmetic, logical, geometric rules
Information synthesis
- Scale transfers
- Geostatistics and interpolation
- Changes in spatial location
Optimization techniques
- Optimal locations
- Shorter paths, operational research
Classification methods
Descriptive classification (grouping on a descriptive criterion)
- Maintain the form of the distribution
- Maintain dispersion: maximize the interclass variance
- To reveal the irregularities of the series
Discretization methods (examples)
- Classes of the same amplitude
- Equal enrolment classes (quantiles)
- Use of mean and standard deviation (normal distributions)
- Arithmetic or geometric progression
- Natural Threshold Method
Examples of methods using localization
- Selection of objects on a distance or membership criterion: the creation of buffer zones (or buffer, or mask)
- Selection of objects based on orientation or direction criteria
- Connecting objects on a criterion of distance or belonging: crossings, hierarchy, aggregation, belonging
- Classification by proximity: grouping on a geometric or topological criterion (aggregates)
- Proximity and neighborhood operations: geostatistics and interpolation
Changes in the type of geometric object
- From point to point objects: point to the mesh by interpolation, point to the zone by influence (Voronoi) or aggregation, point to the line by creating curves of aggregation
- From the objects line to line: line to the zone by expansion or aggregation (weighted by an interaction distance), the line to point (calculation of centroids), the line to mesh by interpolation
- From the zone objects: zone to point (centroid), zone to the line (skeletonization), zone to mesh (rasterization)
- From mesh objects: mesh to the area (vectorization), mesh to mesh (rasterization and resampling methods)
GIS and remote sensing
Geo-referencing and mosaics
- Geometric transformations and photogrammetry
- Adjustment and adjustment of values
Which object: point or area?
- From pixel to geographical object: processing by zone or by pixel?
- The use of semi-joining and aggregation operations
Conventional methods in remote sensing
- Different types of satellites, different methods: channels are attributes, indices are methods
- Directed and non-directed classifications
- Vegetation, building, texture, structure, etc. indices Morphology math.
Urban remote sensing
- Aerial photography and orthophoto plans
GIS and interpolation: digital field models
DTM by interpolation
- From points or lines by interpolation
- Many methods to move from the point to the area: nearest neighbors, inverse distance, Splines, kriging, etc. (deterministic methods vs. probabilistic methods).
DTMs and their methods
- Slope, orientation, drains, flows, volumes, visibility, watersheds, etc. Hydrology models.
Representation by illumination, representation in perspective
Distance models, influence models, influence areas
GIS and optimization
Networks and graphs
- operational research applications: optimal path
- distances along with a network, accessibility problems
Cartography
Cartographic language and graphic semiology
The cartographic language
- The components of cartographic language
- The elementary graphic signs (point, line, task), the cartographic figurative (built from the elementary signs), the graphic layout (punctual, linear, zonal), the visual variables (shape, size, color, value, orientation, texture-structure, grain).
GIS and mapping
- Automatic mapping from a query
- Choice of a cartographic projection
- Association descriptive attribute - graphics attribute (figurative, layout, visual variables)
- Automatic label positioning
- Filtering and generalizations
Dressing a map
- Graphic scale
- North Arrow
- Title
- Corps Map
- Legend
- etc...
GIS and the Internet
Software: different organizations
- Application and data on a single computer at the customer's premises
- The client application and data server over the local area network
- Data server and application server over the local area network
- Data server and Internet application server, query using an Internet browser
Remote interrogation, dedicated applications
-An "application" organization-A Client/Server organization
-A server managing the database, responding to requests
-On the customer side, several solutions, for dedicated applications:
- CGI
- Applet or ActiveX
- ASP .Net
- JSPX
- SVG
Available data of uncontrolled quality
- Data and metadata: an essential requirement
- Quality that is often difficult to assess, data to handle with care, unknown contexts
- Extraordinary data servers (USGS, NASA, Google...), but whose free availability is not guaranteed in the long term
- Multiple questions on data/information/knowledge ownership
GIS: organization
Project definition and feasibility study
- Drafting of specifications describing the objectives and needs of the application.
- Evaluation of the necessary data and acquisition flows.
- Assessment of the system specifications and objectives in relation to existing systems on the market, to assess the feasibility of the operation and the costs involved.
- Final evaluation of the various possible choices in terms of benefits and costs.
Logical organization and functional implementation
- General implementation and administrative body (human and financial needs, training and user assistance plans, management of future system evolution based on operating results)
- Data acquisition body to manage the various information flows (regular or application-specific flows). This body is responsible for evaluating and describing information sources, access procedures, and acquisition procedures.
- Data entry and integration body: structuring, homogenization, validation, coding, coding, entry, control, correction, and integration of data according to the techniques required by the information system.
- Data analysis and exploitation body ensuring that user requests and application needs are met according to the specifications.
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