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GEOGRAPHICAL INFO SYSTEM

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ICGE 2012 - December 3-4,2012 (Paper No. D005)

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GIS flow model Types of Errors Propagation Of Errors Modeling Techniques

Geographic Information System:

Geographic Information System Geographic – 80% of government data collected is associated with some location in space Information - attributes, or the characteristics (data), can be used to symbolize and provide further insight into a given location System – a seamless operation linking the information to the geography – which requires hardware, networks, software, data, and operational procedures …not just software! …not just for making maps!

1. GIS Flow Model:

Capture Data 1. GIS Flow Model Register Map Base Interpret Data Convert Data to Digital Format Store Data in Computer Process Data Display Results

Challenges of GIS:

Challenges of GIS

Accuracy and Precision:

Accuracy and Precision

ERROR AND UNCERTAINTY:

ERROR AND UNCERTAINTY

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SOURCES OF ERROR

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HANDLING ERROR

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HANDLING ERROR

TIME LINE:

TIME LINE ACTION PREDICTION FORECASTING PRESENT FUTURE

Black Box Model:

Black Box Model S/M INPUT OUTPUT PSEUDO BLOCK MODEL

2. TYPES OF ERRORS:

2. TYPES OF ERRORS GROSS ERRORS RANDOM ERRORS SYSTEMATIC ERRORS

GROSS ERRORS :

GROSS ERRORS Caused due to carelessness and human errors Prevention by series of checks and implementing sound procedures that minimize the opportunities for these types of errors to occur

RANDOM ERRORS :

RANDOM ERRORS Are intrinsic to the measurement process. & exhibit definite statistical behaviour. Random errors can only be eliminated by carefully examining large amounts of redundant data Minimization Careful measurement Measurement system design

SYSTEMATIC ERRORS :

SYSTEMATIC ERRORS Caused by mismatch between Models of the process we are using Reality of the process Detection By Analysis of error propagation By sensitivity analysis By parameter evaluation

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Initial processing errors Topology Layer Matching Edge Matching Topological Construction Feature Identification Lineage

LAYER MATCHING :

LAYER MATCHING

Lineage or processing history :

Lineage or processing history A collection of states representing the changes that have occurred over time in a versioned geo database.

Metadata :

Metadata Metadata is data about data. It is a summary document providing : content, quality, type, creation, and spatial information about a dataset.

Meta data Analysis:

Meta data Analysis

Digitizing and Geocoding Errors :

Digitizing and Geocoding Errors Processing errors occur during other phases of data manipulation such as : Digitizing and geocoding. Overlay and boundary intersections. Errors from rasterizing a vector map. Physiological errors of the operator may result in : Spikes. Switchbacks. polygonal knots. loops . Again you cannot be lazy!

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Data Structure…. GIS GRAPHIC ALPHA NUMERIC VECTOR RASTER CO-ORDINATE SYSTEM IMAGE AREAL PHOTOGRAPH REMOTE SENSED SCANNED IMMAGES

Vector and Raster data:

Vector and Raster data The vector model is extremely useful for describing discrete features, but less useful for describing continuously varying features such as soil type or accessibility costs for hospitals. The raster model has evolved to model such continuous features. A raster image comprises a collection of grid cells rather like a scanned map or picture. What is the resolution of the data? If raster, report cell size If vector, report scale

Comparison of Raster and Vector Formats:

Comparison of Raster and Vector Formats Most GIS software can display both raster and vector data. Only a limited number of programs can analyze both types of data or make raster type analyses in vector formats.

3. PROPAGATION OF ERRORS::

3. PROPAGATION OF ERRORS: Propagation occurs when one error leads to another , Eg: If a map registration point has been mis-digitized in one coverage and is then used to register a second coverage, the second coverage will propagate the first mistake. In this way, a single error may lead to others and spread until it corrupts data throughout the entire GIS project. How To avoid this problem ? ? ? u se the largest scale map to register your points Σ

Why Use GIS in Schools? :

Why Use GIS in Schools?

Why Use GIS in Schools?:

Why Use GIS in Schools? Encourage seminars demonstrating applications Establish a networking organization encompassing all interested disciplines Teach a class or lab for a department outside of your own Organize or team-teach a discipline-oriented workshop with a domain expert Write proposals for non-GIS teaching, research and outreach Consider adopting a Spatial STEM approach that translates grid-based map analysis operations into a mathematical/statistical framework that serves as the communal language of science, technology, engineering and mathematics disciplines

GIS as infrastructure:

GIS as infrastructure Virtual Globes Desktop GIS Server GIS Mobile GIS PC, PDA Phone Network DBMS Files XML Geo databases 4. Modeling Techniques

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CONCLUSION – Gross errors are largely caused by carelessness and human error. Systematic errors are caused by a mismatch between the models of the processes Random errors are intrinsic to the measurement process

REFERENCES ::

REFERENCES : BURROUGH, P.A., 1986. Principles of Geographical Information Systems for Land Resources Assessment. Oxford, UK : Oxford University Press. CASSETTARI , S., 1993. Introduction to Integration Geo-Information Management. London : Chapman and Hall. CHRISMAN, N.R., 1983. The role of quality information in the long-term functioning of a geographic information system. Cartographica 21 : 79. CHRISMAN, N.R., and LESTER, M.K., 1991. A. Diagnostic Test for Categorical Maps. Technical Papers 1991 ACSM – ASPRS Anual Convention, Vol.6, pp. 330-348. CHRISMAN, N.R., 1998. Rethinking Levels of Measurement for Cartography. Cartography and Geographic Information System, Vol. 25, No. 4, pp. 231 – 242. DALE, P.F., and MCLAUCHLIN , J.D., 1999. Land Information Management. Oxford University Press. LAURINI, R., and THOMPSON, D., 1992. Fundamentals of Spatial Information Systems. Sand Diego : Academic Press. STAR, J.L and J.E. ESTES, 1990. Geographic Information Systems : An Introduction, Prentice Hall.

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Thank you. QUERRIES ? ? ?

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One More Thing SYSTEM DYNAMICS

Grid sampling examples within hexagonal grid :

Grid sampling examples within hexagonal grid A number of GIS software packages, such as  TNTMips ,  ENVI ,  Idrisi  and  GRASS  provide tools to assist in the selection of sample points

Ontology-based model of space, time, and theme. Spatial Occurrents and Named Places are directly linked with Spatial Regions which record their geographic location. Temporal intervals on relationships denote when the relationship holds (valid time).:

Ontology-based model of space, time, and theme. Spatial Occurrents and Named Places are directly linked with Spatial Regions which record their geographic location. Temporal intervals on relationships denote when the relationship holds (valid time). Courtsey : Analyzing Theme, Space, and Time: An Ontology-based Approach By Matthew Perry – ACM 2006

Vector and Raster Formats:

Vector and Raster Formats Most GIS software can display both vector and raster data. Raster formats are efficient when comparing information among arrays with the same cell size. Raster files are generally very large because each cell occupies a separate line of data. Vector formats are efficient when comparing information whose geographical dimensions are different.

How to Geomask:

How to Geomask Outside a GIS Can perform arithmetic on X and Y (latitude and longitude fields) Can set a minimum or maximum distance based on population density (urban vs rural) Inside a GIS Generate a random point within a circular buffer Add a population density layer to decide min/max distances Can avoid placing points “out of bounds”

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Geocoding Matches? Score Matches Input Address Parse Address Generate Soundex for Address Name List Candidates: No. Range,Zone yes no Best Score >= 90? Output Address Output Rejects yes no Correct Addresses or Map

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T IGER OPOLOGICALLY NTEGRATED EOGRAPHIC NCODING EFERENCING U.S. Census Bureau TIGER GEOCODER

Software Used:

Software Used Arc/Info IDRISI Also use: ER-Mapper, ERDAS, Atlas*GIS

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Geographic Information Systems and Science, 3rd ed. by Longley, Goodchild, Maguire, and Rhind Textbooks

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GIS Tutorial 2: Spatial Analysis Workbook for ArcGIS 10, 2nd ed. by Allen Textbooks

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Place Matters: Geospatial Tools for Marine Science, Conservation, and Management in the Pacific Northwest edited by Wright and Scholz Textbooks

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To most folks on campus, geotechnology is simply a set of highly useful apps on their smart phone or a 3D fly-by anywhere in the world— in a sense trivializing GIS. 

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Source : Map Analysis , Joseph K. Berry, University of Denver; GeoTec Media publisher

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