WFM 6202: Remote Sensing and GIS in Water Management

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WFM 6202 Remote Sensing and GIS in Water
Management
Part-B Geographic Information System (GIS)
Case study Generation of rainfall contour map
using spatial analysis of GIS

• Akm Saiful Islam

Institute of Water and Flood Management
(IWFM) Bangladesh University of Engineering and
Technology (BUET)
February, 2008
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Problem statement

• This case study will show how to generate a
  rainfall contour map of over Bangladesh based on
  the data collected in different rain gauge
  stations.
• Given data
• A shape file which contains different Thana
  boundary of Bangladesh
• A text file contains locations of rain gauge
  stations and mean daily rainfall values (mm/day)
  of that station

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Outline of the Exercise

• Create a Shape file of rain gauges from station
  data in a ASCII text file
• Creating District map of Bangladesh using
  generalization technique from Thana map of
  Bangladesh.
• Create rainfall contour map of rainfall of
  Bangladesh by surface interpolation

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Add Thana Shape file of Bangladesh
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Create District Maps from Thana Maps

• Click on Dissolve tools
• Select District name field

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District Maps of Bangladesh with unique color
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Change Layer Property

• Double click on the Layer
• Select Categories from Symbology tab
• District name as Value Field
• Click on Add All values
• You can also change color scheme

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District Map of Bangladesh
Rename the layer as District
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Add Rainfall Text files as table

• Click on Add Data and select rainfall.txt
• Open it as table

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Table of Rainfall Data
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Create Shape file from Rainfall table

• Click on Make XY Event Layer
• Select rainfall table
• Longitude as X Field and Latitude as Y field

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Rain gauge stations as shape file
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Rain gauge stations

• Label features

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Turn on Spatial Analyst Extension

• First load the Spatial Analyst
• click on Tools gt Extension
• Check the box left to Spatial Analyst

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Masks Interpolation region

• Click options from Spatial Analyst
• Select District as analysis mask

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Step-7 Create contour of rainfall by surface
interpolation

• Click Surface gt Interpolate Grid
• Select Output grid extent as Disolv1.shp
• Select MeanDailyRain as Z Value Field

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Interpolation using IDW method

• Click on IDW method of interpolation
• Select Z value field as MeanDailyRain

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Rainfall map of Bangladesh
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Find Mean Rainfall for each district

• Click Zonal Statistics

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Zonal statistics for each distric
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Rainfall in each district of Bangladesh

• Change symbology of district maps to zstat.MEAN
• Turn on Label