Geographical Information Science and remote sensing and analysis

GIS

1. REAL WORLD AND ITS REPRESENTATION, GEOGRAPHIC PHENOMENA PRESENTED BY B. LINDA THERES M.TECH GEOINFORMATICS SEMESTER-1 PRINCIPLES OF GIS DEPARTMENT OF GEOGRAPHY, BDU

2. CONTENTS Purpose of GIS Real World Representations Geographic Phenomena Types of Data Values Boundaries References

3. PURPOSE OF GIS Urban Planner Biologist Natural Hazard Analyst Geological Engineer Mining Engineer Forest Manager Hydrological Engineer

4. REAL WORLD REPRESENTATIONS Decision Making Modelling Map Database Spatial Database

5. MODELLING The representation will have certain characteristics in common with the real world. we can ‘play around’ with the model and look at different scenarios to answer ‘what if’ questions. We can change the data in the model, and see what are the effects of the changes. Types Static Models (Maps & Databases) Dynamic or process models (Simulation Models)

6. MODELLING

7. MAPS 2D static representation Influenced by accuracy of base data Cartography as the science and art of map making functions as an interpreter translating real world phenomena (primary data) into correct, clear and understandable representations for our use Analog Cartography Displayed on given scale Choice of scale was tedious Digital Cartography No more a storage trunk Completely for visualization

8. MAPS

9. MAPS

10. DATABASE A database is a repository capable of storing large amounts of data. It comes with a number of useful functions: Concurrent use Storage optimization Data integrity Query facility A database design determines which tables will be present and what sort of columns (attributes) each table will have. A completed database design is known as the database schema.

11. DATABASE

12. SPATIAL DATABASES store representations of geographic phenomena focuses on the functions: concurrency, storage, integrity, and querying, especially, but not only, spatial data GIS, on the other hand, focuses on operating on spatial data The assumption for the design of a spatial database schema is that the relevant spatial phenomena exist in a two- or three-dimensional Euclidean space. The phenomena that we want to store representations for in a spatial database may have point, line, area or image characteristics.

13. SPATIAL DATABASE Cities on a map may have to be represented as points or as areas, depending on the scale of the map. To support this, the database must store representations of geographic phenomena (spatial features) in a scaleless and seamless manner. Phenomena are classified into thematic data layers depending on the purpose of the database for example, a cadastral, topographic, land use, or soil database. A spatial database not only serves to store the data and manipulate it, as it should also allow the users to carry out simple forms of spatial analysis.

14. GEOGRAPHIC PHENOMENA a geographic phenomenon is something of interest that can be named or described, can be georeferenced, and can be assigned a time (interval) at which it is/was present.

15. GEOGRAPHIC PHENOMENA

16. GEOGRAPHIC PHENOMENA TYPES Any geographic phenomenon can be represented in various ways; the choice which representation is best depends mostly on two issues: what original, raw data (from sensors or otherwise) is available, and what sort of data manipulation does the application want to perform.

17. GEOGRAPHIC PHENOMENA TYPES Observations made What it is (name) Where it is (georeferencing) Types Geographic field (Discrete ) - eg : LULC, soil class, etc (Continuous) - eg : Temperature, Pressure, etc Geographic objects A general rule-of-thumb is that natural geographic phenomena are more often fields, and man-made phenomena are more often objects.

18. GEOGRAPHIC FIELD A (geographic) field is a geographic phenomenon for which, for every point in the study area, a value can be determined. Types : Discrete, continuous A field-based model consists of a finite collection of geographic fields

19. GEOGRAPHIC FIELD Figure: A continuous field example, namely the elevation in the study area.

20. GEOGRAPHIC FIELD Figure: A discrete field indicating geological units, used in a foundation engineering study for constructing buildings

21. GEOGRAPHIC OBJECT Geographic objects populate the study area, and are usually well distinguishable, discrete, bounded entities. The space between them is potentially empty. Their position in space is determined by a combination of one or more of the following parameters: location (where is it?), shape (what form is it?), size (how big is it?), and orientation (in which direction is it facing?). Dimension- point, line, area or volume

22. GEOGRAPHIC OBJECT not study geographic objects in isolation, but whole collections of objects viewed as a unit. The most common (and obvious) of these is that different objects do not occupy the same location. Useful to look at characteristics like coverage, connectedness, capacity and so on. Which part of the road network is within 5 km of a petrol station? (A coverage question) What is the shortest route between two cities via the road network? (A connectedness question) How many cars can optimally travel from one city to another in an hour? (A capacity question)

23. GEOGRAPHIC OBJECT Figure: A number of geological faults

24. KINDS OF DATA VALUE Nominal data values or categorical data name Ordinal data values Compare (high, medium, low) Interval data values no arithmetic zero value, and does not support multiplication or division. For instance, a temperature of 20 o C is not twice as warm as 10 o C rational data values Distance in metres

25. BOUNDARIES Where shape and/or size of contiguous areas matter, the notion of boundary comes into play. This is true for geographic objects but also for the constituents of a discrete geographic field Location, shape and size are fully determined Crisp and fuzzy boundary As a general rule-of-thumb—again—crisp boundaries are more common in man-made phenomena, whereas fuzzy boundaries are more common with natural phenomena.

26. REFERENCES http://www.esri.com/what-is-gis http://www.itc.nl/library/papers_2009/general/PrinciplesGIS.pdf

27. QUERIES