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What is Object-Based ImageAnalysis?                                                          Kirk Benell              The ...
Object-Based Image AnalysisWhat is an object?• An object is a region of interest  with spatial, spectral (brightness  and ...
Object-Based Image AnalysisTraditional pixel-based classification  •   Based on reflectance values of pixels  •   Works fo...
Pixel-based Classification                                       1.0                                                      ...
Object-Based Image Analysis Image                     Segmented      Merged                                               ...
Object-Based Image Analysis• Greater accuracy from input: tone, color, texture, shape, size,  orientation, pattern, shadow...
ENVI Feature Extraction• Uses an object-based approach to classify imagery• The ENVI tool provides an easy to use method f...
ENVI Feature ExtractionNeeds for Feature Extraction  • Increased availability of high-    resolution images  • Manual digi...
ENVI Feature ExtractionWorkflow:  • Spectral/spatial/texture attributes  • Object-based fuzzy rule-based    classification...
ENVI Feature Extraction                         Input Data                                                           Objec...
Image Segmentation Scale Level   A low scale level provides more           A high scale level provides fewersegments in th...
Segmentation        scale level = 50Visual Information Solutions
Under segemented        scale level = 70Visual Information Solutions
Over segmented        scale level = 30Visual Information Solutions
Merge to aggregate        adjacent segmentsVisual Information Solutions
Select Classification Method• Select Classify by  Selecting Examples to  select training data and  perform a supervised  c...
View attributes to     characterize feature     of interestVisual Information Solutions
Create rules to define      features of interestVisual Information Solutions
ENVI Feature ExtractionSpatial Attributes  • Region area, length, compactness, convexity, solidity, form factor,     recta...
Preview      classification results      and adjust training      data on-the-flyVisual Information Solutions
Export features as one      or individual vectorsVisual Information Solutions
View Feature Extraction Report•   View parameters    used and statistics    of exported vectors•   Save as a text    repor...
• Edit vector properties      • View Attribute        Information      • Square-up building        sides      • Smooth vec...
• Push data into ArcMap for         further analysis and vector         editing       • Add imagery and new vector        ...
Thank You   Visual Information Solutions
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What is Object-Based Analysis

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Transcript of "What is Object-Based Analysis"

  1. 1. What is Object-Based ImageAnalysis? Kirk Benell The information contained in this document pertains to software products and services that are subject to the controls of the Export Administration Regulations (EAR). The recipient is responsible for ensuring compliance to all applicable U.S. Export Control laws and regulations.
  2. 2. Object-Based Image AnalysisWhat is an object?• An object is a region of interest with spatial, spectral (brightness and color), and/or texture characteristics that define the region• Pixels are grouped into objects, instead of single pixel analysis• May provide increased accuracy and detail for classification purposes Visual Information Solutions
  3. 3. Object-Based Image AnalysisTraditional pixel-based classification • Based on reflectance values of pixels • Works for low and medium resolution imagery • Works for mass area-based features • Multispectral or hyperspectral imageryLimitations of pixel-based analysis • Only spectral, seldom spatial and contextual • Results with inconsistent salt-and-pepper noise • Inaccurate borders for texture computation • Limited extraction of small-scale objects Visual Information Solutions
  4. 4. Pixel-based Classification 1.0 Water Pixels Image 0.5 6 5 4 3 2 0.0 1 1.0 Veg Reflectance 0.5 0.0 1.0 Soil 0.5 0.0 1 2 3 4 5 6 BandGroup materials based on their reflectanceresponse per pixel Visual Information Solutions
  5. 5. Object-Based Image Analysis Image Segmented Merged Feature Pixels Objects Segmented The Letter ‘E’ Objects• Group contiguous pixels into objects• Objects are classified into feature classes based on their spatial, textural and spectral attributes Visual Information Solutions
  6. 6. Object-Based Image Analysis• Greater accuracy from input: tone, color, texture, shape, size, orientation, pattern, shadow, situations• Advanced visualizations: Computer vision technique using image segmentation• Use homogeneous regions as basic analysis elements• Additional spatial, contextual and semantic information Visual Information Solutions
  7. 7. ENVI Feature Extraction• Uses an object-based approach to classify imagery• The ENVI tool provides an easy to use method for extracting information from panchromatic, multispectral, hyperspectral, and elevation data • Vehicles • Buildings • Transportation • Natural Features Visual Information Solutions
  8. 8. ENVI Feature ExtractionNeeds for Feature Extraction • Increased availability of high- resolution images • Manual digitization, labor intensive • Semi-automated solution is highly desiredApplications • Defense and Intelligence • Geographic Information Systems • Transportation • Urban planning and mapping Visual Information Solutions
  9. 9. ENVI Feature ExtractionWorkflow: • Spectral/spatial/texture attributes • Object-based fuzzy rule-based classification • Object-based supervised classificationPreview Window for instant feedback prior to processing an entire imagePost-Classification Vector Tool • Centerline extraction • Snapping, smoothing • Vector editing Visual Information Solutions
  10. 10. ENVI Feature Extraction Input Data Object Image Segmentation Generation Attribute Computation for Object Primitives Rule Base Feature Selection Object-Based Classification Decision Making Supervised Classification Extracted Features/Classes Visual Information Solutions
  11. 11. Image Segmentation Scale Level A low scale level provides more A high scale level provides fewersegments in the final processed image segments in the final processed image The Preview Window provides on-the-fly feedback for the selected Scale Level Visual Information Solutions
  12. 12. Segmentation scale level = 50Visual Information Solutions
  13. 13. Under segemented scale level = 70Visual Information Solutions
  14. 14. Over segmented scale level = 30Visual Information Solutions
  15. 15. Merge to aggregate adjacent segmentsVisual Information Solutions
  16. 16. Select Classification Method• Select Classify by Selecting Examples to select training data and perform a supervised classification• Select Classify by Creating Rules to select attribute parameters to perform a classification• Select Export Vectors to export without performing a classification Visual Information Solutions
  17. 17. View attributes to characterize feature of interestVisual Information Solutions
  18. 18. Create rules to define features of interestVisual Information Solutions
  19. 19. ENVI Feature ExtractionSpatial Attributes • Region area, length, compactness, convexity, solidity, form factor, rectangular fit, roundness, elongation, main axis direction, axes length, number of holes, hole/solidity ratioSpectral Attributes • Band minimum, maximum, average and standard deviationTexture Attributes • Variance, range, mean, and entropyColor Space and Band Ratio • Hue, saturation, intensity, NDVI, NDWI, other ratios Visual Information Solutions
  20. 20. Preview classification results and adjust training data on-the-flyVisual Information Solutions
  21. 21. Export features as one or individual vectorsVisual Information Solutions
  22. 22. View Feature Extraction Report• View parameters used and statistics of exported vectors• Save as a text report to share with colleagues Visual Information Solutions
  23. 23. • Edit vector properties • View Attribute Information • Square-up building sides • Smooth vectorsVisual Information Solutions
  24. 24. • Push data into ArcMap for further analysis and vector editing • Add imagery and new vector layer to GIS databaseVisual Information Solutions
  25. 25. Thank You Visual Information Solutions
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