Gis Concepts 1/5
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The document discusses the concepts and functions of Geographic Information Systems (GIS) and their role as information systems in managing spatial data. It explains how GIS technology allows for the creation, management, and analysis of spatial databases, supporting decision-making processes by providing insights into geographic realities. Key topics include spatial data modeling, geo-referencing, database management, and the distinction between traditional maps and dynamic spatial databases.
Gis Concepts 1/5
- 1. Concepts and Functions of Geographic Information Systems (1/5) MSc GIS - Alexander Mogollon Diaz Department of Agronomy 2009
- 2. Concepts and Functions of GIS .PPT Topic #1 Topic #2 Topic #3 1 A GIS is an information system GIS is a technology 2 Spatial Data modelling Sources of data for geodatasets Metadata 3 Geo-referencing Coordinate transformations 4 Database management 5 Spatial Analysis
- 3. Maps Are the traditional instrument to describe the world as it was, is, will (probably) be, we want it to be Topographic and thematic maps Cadastral plans Photo-maps, Satellite image based maps
- 4. Map scale = 1:50.000
- 5. Photo scale = 1:10.000
- 6. Plan scale = 1:2.500
- 7. Maps Display the location and shape of entities of the real world (geographic reality) Describe the state of geographic reality at a given moment in time Give meaning to displayed entities by symbolisation according to a map legend Information content is related to map scale Are static, difficult to update
- 8. Plans / Sketches Plans and sketches are the traditional instruments to describe the world as we want it to be
- 9. Plan scale = 1:2.500
- 10. Spatial databases With the advent of GIS-technology, a new instrument is introduced: the spatial database Data describing geographic reality are no longer stored in maps, plans and sketches but in digital databases GIS-software provides tools to create and work with spatial databases to produce maps … enhance knowledge support decisions
- 11. From data collection to database A/D conversion Structuring Computing functions Other functions Data collection Database Information System
- 12. From data collection to database Data about entities : persons associations companies licences invoices municipalities, districts properties, …
- 13. Data about entities Persons Associations Companies Invoices Insurance contracts Provinces Parcels Buildings … . Date of birth, ... List of members, ... List of employees, ... Due date of payment, ... Insured risks, ... Capital city, ... Owner, ... Construction cost, ...
- 14. Database = structured collection of digital data If not acquired in digital form, data need to be converted from analogue to digital form Structuring is required to facilitate search and query of the data: Tables are often used to structure the data Several software packages/tools exist to integrate data in tables for further processing MS-Access, MS-Excel, dBase, … are table- (row/column) based Data collections contain very frequently an implicit indication of location: address, administrative/statistical unit, ...
- 15. From database to information system
- 16. From database to information system Data about entities : persons associations companies licences invoices municipalities, districts properties, … What ? Wen ? What if ?
- 17. Information system Database equipped with tools which allow to ask questions and obtain answers Information = structured and interpreted data, fit for specific use Information = data put in its context to allow for interpretation Information is derived from data using transformation tools query tools computing tools advanced analytical tools presentation tools
- 18. Questions about entities Persons Associations Companies Invoices Insurance polices Provinces Parcels Buildings … . How old ? When 18 ? How many members ? Monthly salary cost ? Amount unpaid ? How large the risk ? Budget deficit ? (Un)built ? For students ? What if taxes rise with 10% ? What deficit if #students decrease to 25.000 ?
- 19. From database to information system What ? When ? What if ? WHERE ?
- 20. From maps and other collections of spatial data to GIS Data about spatial entities rivers, hydrography spatial destination zones muncipalities properties, buildings ... What ? When ? What if ? WHERE ?
- 21. Spatial entities (1) Cadastral entities, properties, buildings Patrimonium Unbuilt parcels Domicilies Entities related to spatial planning Transport infrastructure (road, railway, public transport connection, water- and airways,...) Zones with a defined spatial destination Zones with an effective land use ...
- 22. Spatial entities (2) Entities related to security policy Location of traffic accidents Properties where theft occurred … Entities for planning of natural resources Fossil fuel fields Mining zones Fishing areas Natural reserves UNESCO world heritage
- 23. Spatial entities (3) Entities related to agricultural and environmental policies Agricultural zones and parcels Irrigation and drainage canals Water abstraction points Zones for soil erosion abatement Other entities Location of wind mills Mangrove patches Traffic lights Sewer lines, electricity lines
- 24. From data on spatial entities to spatial information From data regarding buildings, demography, migration to requirements for housing From data regarding (non-) irrigated agricultural land, soils and climate to rice production capacity by province From data on factories and owners of cars to air quality distribution From data regarding beach resorts to regional touristic potential
- 25. Spatial entities and spatial objects Spatial entities Are elements of geographic reality with a clear boundary ‘crisp’ Spatial entities of a given type are grouped into classes of spatial entities Data about spatial entities can be implicitly spatial (adresses, other indirect references) or explicitly spatial (coordinates) Incorporation in a gDB of spatially explicit data about spatial entities requires abstraction and modelling Spatial entities are abstracted and modelled as spatial objects ‘ Feature’ is used as a synonym for both ‘entity’ and ‘object’ Spatial objects Spatial objects have: a location expressed according to a known reference system A geometric shape: point, line, area/polygon, volume, one or more cells (pixel), voxel (3D-cells or cubes) descriptive attributes (characteristics, properties, behaviour) Objects of the same shape-type and sharing the same attribute structure belong to one object class. Such class has most often more than one member
- 26. An Example
- 27. Y X 6045 Identification Name 6045 Land Use
- 28. Y X 101 Building 101 Name Identification
- 29. Y X A00233 99-nov-16t A00233 Date Identification
- 30. The real world = spatial entities + ??
- 31. Terrain Geographic reality is more than classes of spatial entities The spatial continuum or Terrain in which entities occur Elevation (shaping relief and landscapes) Depth of lakes, aquifers Concentration of toxic substances in soil, surface water, … Air quality Noise, … Terrain = spatially variable characteristics of individual locations Each terrain characteristic (e.g. elevation) is modelled as a Digitaal Terrain Model (DTM) of ‘single valued surface’ (surface)
- 32. From spatial database to GIS Data about spatial entities and/or terrain rivers, hydrography spatial destination zones muncipalities properties, buildings elevation, bathymetry, … What ? When ? What if ? WHERE ?
- 33. gDB contains data about spatial entities and/or terrain All geographic data have three components: A geometric component: defines the position and shape of objects/locations with respect to a reference system; ALWAYS present A descriptive component : attaches characteristics or attributes to objects or locations Time as the third component. Locations and/or characteristics can change over time Geographic primitive = most elementary building block for the description of the geometric component of spatial entities and terrain Points Cells
- 34. Data in a gDB must be structured and interpreted Structuring of the geometric primitives ‘point’ or ‘cell’ into 2D-geographic objects : Elementary point, line, polygon objects More complex network, region objects Cells and aggregations of cells Linked to ATTRIBUTE-information into 2.5D surfaces (for terrain characteristics): Relief, groundwater, noise into 3D-geographic objects (volumes)
- 35. Example of geometric structuring Y X Points are structured into lines which define 2D-polygons
- 36. Example of geometric structuring Points/cells are structured into 2.5D surfaces
- 37. Data in a gDB must be structured and interpreted Interpretation of the geometric object- and surface structures through coupling with identification codes and characteristics: Object classes with individual members: specific parcels, water courses, land use zones, … Surfaces which model specific terrain characteristics (e.g. digital elevation model; digital noise intensity model)
- 38. Geographic databases Database = geographic database if it contains data about: Location (Shape) (Characteristics) of geographic objects and/or about terrain-characteristics gDB with computing and other functions = GIS
- 39. GI-Systems Are information systems; allow the user to formulate questions about geographic reality and obtain ‘best possible’ answers Comparable to non-spatial information systems Emphasis is on the geometric component, the ‘Where-question’
- 40. Generic questions for a GIS What is at a given location ? Which type of building ? How deep is the groundwater table ? Where are the entities with the specified characteristics ? Where are the severely degraded zones within the province ? What has changed since ? Which roads have been built since ? Which spatial patterns do occur ? Which is the configuration of atmospheric high and low pressure zones ? Which are the consequences of ? What if ? Which area will flood if a dike is perforated at a given location ?
- 41. GIS = IS GIS = TECHNOLOGY to build and exploit gDBs Spatial data modelling
- 42. GIS = IS GIS = TECHNOLOGY to build and exploit gDBs Management Transformation Visualisation, Query, Cartography Analysis
- 43. GIS as a technology Sets of computer programs, infrastructure and know-how to: A/D-convert Structure Process data about spatial entities and terrain into information Query and communicate this information Based, to an important extent, on database-technology (DBMS) Applicable in each thematic domain for which locations are important Support of decisions
- 44. Summary of important items The world as it is or was; The world as we expect it or want it to be Maps versus spatial databases Spatial entities versus terrain characteristics Nature of geographic information A GIS is an information system that can provide answers to ‘where ?’ and related questions regarding the current, past, expected and planned geographic reality that is based on a model of the geographic reality which is captured in a spatial database (gDB) GIS is a technology which enables to build and exploit spatial models/gDB
- 45. Questions or remarks ? Thank you …