NDVI Calculation of RS Data

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NDVI Calculation of RS Data

• November Seminar-28/11/06
• Shamim Akhter
• PhD Student
• AIDA Lab
• Department of Information Processing
• Tokyo Institute of Technology, Japan

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Aster reflectance image

• ASTER stands for Advanced Space borne Thermal
  Emission and Reflection Radiometer
• ASTER started monitoring global environment
  changes in March 2000 and it provides image.
• Sensor on-board Terra is having 14 spectral bands
  ranging from 15 to 90 m spatial resolution.
• A fifteenth band is a backward view of the NIR
  (15 x 15 m in the 0.76 to 0.86 µm) for
  stereoscopic imaging.
• L1B image can be acquired by ftppull from the
  EROS Data Center Internet website and costs 50
  per image.

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Table 1 Aster Sensor Characteristics

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Modis 8 days reflectance

• MODIS (Moderate Resolution Imaging
  Spectroradiometer) is the key instrument aboard
  the Terra (EOS AM-1) satellite.
• MODIS started functioning in March 2000.
• Terra MODIS is viewing the entire Earth's surface
  every to 2 days, acquiring data in 36 spectral
  bands, or groups of wavelengths.
• Modis sensor on TERRA platform has a spectral
  resolution featuring 36 bands ranging from 250 to
  1000 meters spatial resolution.
• Acquisition of surface reflectance image products
  (MOD09A1) can be done freely through the Eros
  Data Center Internet web site using ftppull
  protocol. Extraction of the binary file can be
  performed for the necessary bands. The date of
  the satellite overpass for this image of central
  Thailand was 13th of March 2000.

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Table 2 MOD09_L3_8-Day Characteristic

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RS Image Handling Libraries

• The remote sensing imagery is generally a common
  type of binary image format (BIL, BSQ, TIFF, etc)
  that is not compressed since the digital numbers
  are of physical meanings to remote sensing
  scientists.
• A particularity of the remote sensing data is
  that it is georeferenced. Meaning that each pixel
  of the images are having a unique location on the
  surface of the Earth.
• Honda (1995) developed a C language based image
  handling library available on the internet
  (http//www.star.ait.ac.th/honda/textbooks/advdip
  /imagelib.zip) and released under the GNU Public
  License (www.fsf.org).
• It has been used for these experiments. It can
  handle jpeg, tiff, ENVI and ER Mapper image
  formats. Currently having georeferencing support,
  the ENVI format is the one used in this
  processing.

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NDVI Calculation

• void NDVI_CALC(int h, int w, u_char nir, u_char
  red, u_char ndvi)
• int i,j
• double wk
• for (i0 ilth i )
• for(j0 jltw j )
• wk (double) ( nirihj -
  redihj ) / (double)( nirihj redihj
  )
• ndviihj wk 100.0
  100.0

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MPI Versions

• The NDVI program is distributed with two
  methodologies and successfully implemented in
  Cluster computers by using MPI Libraries.
• Distributed each pixel.
• Distributed each row.

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• It is observed that there is a point of
  convergence of all curves for a given image with
  an increasing number of operations applied.
• Aster image experiment at 25000 operations shows
  a minimum time processing at about 40 seconds
  with 7 nodes. While the number of operations sets
  tested in the case of Aster image is not enough
  to conclude more with certainty.
• Modis image provides some insights of additional
  operational limits.
• The Modis convergence time of processing is found
  to be about 150 seconds with the maximum node
  number. From the same graph, it seems that above
  1500 operations is the minimum complexity of
  pixel processing that this Modis image would
  benefit from being processed in a distributed
  manner.

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Parallel Methodology
Server 1
Server 2
Client Side
Server n
Row wise distribution is preferred because of
single pixel executions timing is only less
amount of time
Server Side
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Difference with r.vi

• r.vi is a full package.
• r.vi is run able in GRASS environment.
• Where as this NDVI calculation program is simple
  C code.
• r.vi extracts a pixel by pixel information and
  there after distributed whole row at a time.
• Where this C program extracts all pixels
  information (Dr.Hondas C library) and puts them
  in 2D arrays. Then the array is going to
  process.

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Grid Version

• NDVI_ALL folder..

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December Task

• Experiment on the running time for all three
  versions.
• Compare the timing..
• SenseiS requirements
• I will present Introduction about Remote Sensing