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Project Overview

Project Overview. COMPARISON BETWEEN AERIAL DIGITAL ORTHOPHOTO AND SATELLITE IMAGES. GISDATA D.O.O. Ivana Lampek Pavčnik, ivana.lampek@gisdata.hr. Project Goals. COMPARISON: Quality of geometrical corrections Quality of Interpretability Time for defining and ordering

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Project Overview

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  1. Project Overview COMPARISON BETWEEN AERIAL DIGITAL ORTHOPHOTO AND SATELLITE IMAGES GISDATA D.O.O. Ivana Lampek Pavčnik, ivana.lampek@gisdata.hr

  2. Project Goals • COMPARISON: • Quality of geometrical corrections • Quality of Interpretability • Time for defining and ordering • Time for geometric correction • Price

  3. Description • The focus of the project was to examine the results of different type comparisons and discuss the advantages or disavantages between aerial and satellite images FOR MORE INFO... See the final report and procesed data

  4. Data used in project • Aerial black/white photos • Area of interest: city Karlovac and environment • Area: 42000 m2 • Scale of expose: 1:20000 • Number of frames: 10, spatial resolution=0,5m • Date: • For the frame 317: 04. 05. 2000. • For the frame 2/1: 29. 02. 2000

  5. Data used in project • Color aerial photos • Area of interest: city Karlovac and environment • Area: 27000 m2 • Scale of expose: 1:20000 • Number of frames: 6, spatial resolution=0,5m • Date: • May, 2002.

  6. Data used in project • IKONOS satellite images • Area of interest: city Karlovac and environment • Area: 57 000 m2 • Number of frames: 2, spatial resolution=1m • Date: • May, 2003.

  7. Technology • Digital Photogrammetry for geometrical corrections

  8. Digital Photogrammetry • Goal: Creating Orthos • Means • Aerial Triangulation • Orthorectification

  9. Why ORTHOrectify? • There are geometric errors associated with satellite images and aerial photographs • Errors are caused by: • Scale Variation • Sensor Attitude/Orientation • Internal Sensor Errors • Orthorectification removes these errors

  10. 2 cm • 6 cm Scale Variation • House width = 8m • Scale is 1:400 • Scale is 1:133 • Scale varies across the photography

  11. Scale Variation • House width constant (8m), width in photographs varies, therefore scale varies

  12. Differences between aerial triangulations • Aerial photos> to establish Image Coordinates • Provided in a Camera Calibration Certificate • Parameters defining this geometry are: • Focal length • Radial Lens Distortion • Principal Point • Fiducial Coordinates

  13. Image/Focal Plane Focal Length Optical Axis

  14. Internal Geometry of satellite • Usually the internal parameters are read from the image header (SPOT, IRS): • Focal length • Principal point Xo, Yo • Pixel Size • Number of sensor Columns • In the IKONOS and Quick Bird case, the geometry is modeled using rational polynomials • User does not need to define these

  15. Flight Line Characteristics for aerial photos A block should have at least one pair of images that overlap IKONOS or Quick Bird images do not need to have at least one pair of images that overlap

  16. Acquiring Ground GCP Coordinates • Coordinates of GCPs in external orientation can be gathered using various techniques: • Using GPS • From Maps • From other rectified imagery • Should have X, Y and Z values for overlapping aerial images • Should have X, Y for satellite images and Z values from DEM

  17. Image Ground The Influence of Quality Estimates Adjustment process will move points until the “best solution” is found Inputted Standard Deviations (Measures of Quality) The points fluctuate with weighted limits as specified by the standard deviation values Adjustment takes places in the X, Y AND Z direction

  18. Block Residuals • Block of eight images… • Image & ground measurements • Least Squares Adjustment calculates new points based on distributing and minimizing residuals throughout the ENTIRE block • There are RESIDUALS for: • - Each ground point • - Each image point • - Each perspective center

  19. Block Residuals for all data sources • Color Aerial images: • mX mY mZ 0.3239 0.309 0.6507 • B&W Aerial images : • mX mY mZ 0.4175 0.4641 0.4220 • IKONOS: mX mY mZ 0.3879 0.3687 DEM -accuracy

  20. RESULTS of geometrical correction: 2 • 1. Pixel in the DEM (Height) 3 • 2. Parameters of Interior and Exterior Orientation • 3. In the image, a brightness value is determined based on the resampling of surrounding pixels 1 • The orthographic image is constructed by resampling the original image pixels into their new orthorectified positions 4 • 4. Height, Interior and Exterior Orientation information and Brightness Value are used to calculate equivalent location in the Ortho Image • Orthographic Projection

  21. Digital terrain model: • -32 digitized maps with scale 1: 5000 • - equidistance: 5m • summary: 125 878 arcova for generating the surface model

  22. Digital orthophotos • CORRECTED Images as result of ortorectification process • The software takes each DEM pixel and finds the equivalent position in the image. A brightness value is calculated based on the surrounding pixels. This brightness value, the elevation, the interior orientation and exterior orientation information is used to calculate the equivalent location on the ortho image

  23. Quality of interpretability • Automatic interpretation • Defining the level of Image Interpretability Rating Scales

  24. Automatic interpretation • Seed properties> Neighborhood: This option determines which pixels will be considered contiguous to the seed pixel. Any neighbor pixel that meets all selection criteria is accepted and thus, itself, becomes a seed pixel.        If four neighbors are searched, then only those pixels above, below, to the left, and to the right of the seed pixel are considered contiguous.        If eight neighbors are searched then the diagonal pixels are also considered contiguous. Geographic Constraints: This group allows you to enter constraints for the AOI. You can select only one option or use both options. Area: The maximum size of the AOI Distance: specifying a distance from the seed pixel. Spectral Euclidean Distance: The Euclidean spectral distance in digital number (DN) units on which to accept pixels. The pixels that are accepted will be within this spectral distance from the mean of the seed pixel.

  25. SED= 10, AREA=5000 pixels SED= 49, AREA=5000 pixels

  26. SED= 50, AREA=5000pixels

  27. SED= 10, AREA=5000 pixels

  28. SED= 13, AREA=5000 pixels SED= 10, AREA=5000 p

  29. UNSUPERVISED CLASSIFICATION • ISODATA algorithm to perform an unsupervised classification. ISODATA stands for "Iterative Self-Organizing Data Analysis Technique.“ • It is iterative in that it repeatedly performs an entire classification (outputting a thematic raster layer) and recalculates statistics. "Self-Organizing" refers to the way in which it locates the clusters that are inherent in the data. • The ISODATA clustering method uses the minimum spectral distance formula to form clusters. It begins with either arbitrary cluster means or means of an existing signature set, and each time the clustering repeats, the means of these clusters are shifted. The new cluster means are used for the next iteration.

  30. UNSUPERVISED CLASSIFICATION • The ISODATA utility repeats the clustering of the image until either: • a maximum number of iterations has been performed, or • a maximum percentage of unchanged pixels has been reached between two iterations.

  31. Identification of agriculture Identification of forest

  32. Interpretation into 20 category Aerial color image IKONOS image

  33. Defining the level of Image Interpretability Rating Scales • National Imagery Interpretability Rating Scale (NIIRS) > • to define and measure the quality of images and performance of imaging systems • NIIRS has been primarily applied in the evaluation of aerial imagery, it provides a systematic approach to measuring the quality of photographic or digital imagery, the performance of image capture devices, and the effects of image processing algorithms.

  34. Time for defining and ordering • Aerial images in archive: 10-15days • IKONOS in archive: 10-15days • Min.order=100km2 • Quick Bird in archive: 10-15days • Min.order=64km2

  35. Time for geometric correction • Triangulation: • Aerial (10 frames)=2,5 days • IKONOS (2 frames)= 1 day • Ortorectification: the same • Color matching and mosaic: • Aerial b/w (10 frames)=3 days • Aerial color (10 frames)=4 days • IKONOS color (2 frames) =1 day Summary: Aerial color: 7,5 days Aerial b/w: 6,5 days IKONOS color: 3 days

  36. PRICE: • Aerial photos (b/w)= 6,53 €/km2 • Aerial photos (color)= 7,84 €/km2 • IKONOS images = 25,80 €/km2 • Quick Bird = 25,80 €/km2

  37. CONCLUSION

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