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Mapping Water features from SAR Imagery

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Mapping Water features from SAR Imagery

  1. 1. BRAMANTIYO MARJUKI Mapping Water Features From Synthetic Aperture Radar Data REMOTE SENSING
  2. 2. SAR PRINCIPLES Common Things About SAR MAPPING WATER FEATURES Prequisities Download Data From ASF Vertex Image Processing Workflow Water Body Extraction DISCUSSION Remote Sensing for OSM Project
  3. 3. COMMON THINGS SAR DATA Image by : ESA PASSIVE AND ACTIVE REMOTE SENSING
  4. 4. COMMON THINGS SAR DATA Image by : ESA MICROWAVE SPECTRUM USED
  5. 5. COMMON THINGS SAR DATA Image by : ESA SAR Satellite and Sensor Timeline https://vertex.daac.asf.alaska.edu https://earthexplorer.usgs.gov https://www.gportal.jaxa.jp/gp/top.html https://scihub.copernicus.eu/
  6. 6. COMMON THINGS SAR DATA Image by : ESA
  7. 7. COMMON THINGS SAR DATA Image by : ESA Specular Reflection Surface Reflection
  8. 8. COMMON THINGS SAR DATA Image by : ESA Double/Multiple Bounce Volume Scattering
  9. 9. COMMON THINGS SAR DATA Image by : ESA Foreshortening Lay Over Shadow Radar Geometric Errors
  10. 10. COMMON THINGS SAR DATA Image by : ESA Specular Reflection AzimuthScanning alongSatelliteOrbit Range Scanning along Satellite Swath Foreshortening Layover Shadow Surface Reflection
  11. 11. COMMON THINGS SAR DATA Image by : ESA Double Bounce Volume Scattering
  12. 12. MAPPING WATER SAR DATA QGIS + Orfeo Toolbox (advanced Install using OSGEO4W installer) Prequisities
  13. 13. MAPPING WATER SAR DATA QGIS (advanced Install using OSGEO4W installer)
  14. 14. MAPPING WATER SAR DATA Orfeo Toolbox (advanced Install using OSGEO4W installer)
  15. 15. MAPPING WATER SAR DATA QGIS + Orfeo Toolbox (advanced Install using OSGEO4W installer)
  16. 16. MAPPING WATER SAR DATA QGIS + Orfeo Toolbox (advanced Install using OSGEO4W installer)
  17. 17. MAPPING WATER SAR DATA DATA We going to use ALOS PALSAR Radiometrically Terrain Corrected (RTC) data freely available to download from Alaska Satellite Facility (VERTEX) RTC Product designed to be GIS-ready, so user doesn’t need to preprocess the raw data which usually takes time and needs deep knowledge about SAR theories and SAR Processing sequences
  18. 18. MAPPING WATER SAR DATA DATA https://vertex.daac.asf.alaska.edu/
  19. 19. MAPPING WATER SAR DATA WORKFLOW (Two Ways of Mapping) Import Data Logaritmic Scale Conversion Speckle Filtering Histogram Thresholding Feature Extraction Output A Raster to Vector Output B Remove Edge Pixels Error
  20. 20. MAPPING WATER SAR DATA 1. Import Data
  21. 21. MAPPING WATER SAR DATA 2. Despeckle Note that speckle filtering operation will cause improper displayed (blank) image when it is not stretched. This effect happens because speckle filtering leaves very negative pixel value at the edge of the image, and we must fix it at the next step
  22. 22. MAPPING WATER SAR DATA 3. Remove Edge Pixels Error (‘Layer Name’>-9999) * ’Layer Name’
  23. 23. MAPPING WATER SAR DATA 2. Despeckle Pre speckle Post speckle
  24. 24. MAPPING WATER SAR DATA 3. Log Conversion 10* log10 (Layer Name)
  25. 25. MAPPING WATER SAR DATA 4.A Feature Extraction MagicWand Plugin Required Download from Manage and Install Plugins Menu
  26. 26. MAPPING WATER SAR DATA 4.A Feature Extraction MagicWand Plugin Settings Tolerance Tolerance is used to understand if 2 blocks of pixels have similar colors. Example: If the user decides to extract a light green field surrounded by dark green trees to a low value of tolerance must be set. Conversely, if a field that has different shades of yellow is selected to be extracted all at once, the tolerance must be set to a high value. Approximation determines how many pixels must be merged in order to speed up the process. If approximation is increased you will immidiatly notice that the trasparent white area that follows your cursor is increased. . Timeout If a task is taking more than the timeout value (by default 15 seconds), it will be interrupted.
  27. 27. MAPPING WATER SAR DATA 4.A Feature Extraction MagicWand Plugin Settings Set the Raster to multiband Magicwand only working on Multiband Color Render, so if you just have single band raster, just set it up into multiband, but just use same band for every color pane (RGB just use same band) Layer Properties>Style>multiband rendering
  28. 28. MAPPING WATER SAR DATA 4.A Feature Extraction MagicWand Result Result automatically saved in polygon post processing like polygon smoothing still needed Result can be saved directly into Shapefile or other vector data format supported in QGIS
  29. 29. MAPPING WATER SAR DATA 4.B Histogram Tresholding Layer Properties > Histogram Histogram will have bimodal pattern two peak of frequency cumulative, the lower peak usually related to accumulation of water related pixel values
  30. 30. MAPPING WATER SAR DATA 4.B Histogram Tresholding By zooming into the histogram, we could identify the border value of water and land Which is -15,5
  31. 31. MAPPING WATER SAR DATA 4.B Histogram Tresholding Return to STYLE Tab, change the color render to singleband pseudocolor, interpolation to discrete, mode to equal interval, and make just two classes Change the value of first class to -15,5
  32. 32. MAPPING WATER SAR DATA 4.B Histogram Tresholding Result
  33. 33. MAPPING WATER SAR DATA 4.B Histogram Tresholding (make it Permanent) ‘Layer Name’ <= -15.5
  34. 34. MAPPING WATER SAR DATA 4.B Histogram Tresholding (raster to vector)
  35. 35. MAPPING WATER SAR DATA 4.B Histogram Tresholding Result Result automatically saved in polygon post processing like polygon smoothing and cleaning also still needed Result can be saved directly into Shapefile or other vector data format supported in QGIS
  36. 36. Terima Kasih I support throwing words game

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