Uncertainty Introducation This chapter talk about uncertainty discusses

Uncertainty

Introducation This chapter talk about: uncertainty discusses its principles cases and the sources of geographic uncertainty The ways in which they operate in GIS

Techniques for developing uncertainty in GIS It is impossible to make a perfect representation of the world, so uncertainty about it is inevitable. Measurement error is one source of uncertainty. Many geographic representations use inherently vague definitions.

Uncertainty in the conception of geographic phenomena In many cases there are no natural units of geographic analysis. Spatial oil:

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Uncertainty in the conception of geographic phenomena Uncertainty can exist both in the position of boundaries of a zone and in its attributes. Many English terms used to convey geographic information are inherently ambiguous. Ambiguity is introduced when imperfect indicate of phenomena are used instead of the phenomena themselves.

continued Identification of homogeneous zones and spheres of influence lies at the heart of traditional regional geography as well as contemporary data analysis. Relationships typically grow stronger when based on larger geographic units.

Further uncertainty in the measurement and representation of geographic phenomena. uncertainty can often be conceptualized differently under field and discrete object views. A pixel whose area is divided among more than one class is termed a mixel. There are many reasons why measurement of position on the earth’s surface is inherently uncertain. Difficulties in making accurate measurements from maps were a major impediment to early GIS. Many errors in digitizing can be remedied by appropriately designed software.

continued GPS is the first system that allows accurate direct and inexpensive measurement of absolute position on the earth’s surface. Conflation combines the information from two data source into a single source. Datasets with different lineages often reveal unsuspected errors when overlaid. Differences in definitions are a major impediment to integration of geographic data over wide areas.

Further uncertainty in the analysis of geographic phenomena. • uncertainties in data lead to uncertainties in the results of analysis. • Inappropriate inference from aggregate data about the characteristics of individuals is termed the ecological fallacy. • The modifiable areal unit problem can be investigated through simulation of large number of alternative zoning schemes. • Zoning seems similar to sampling but its effects are very different.

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