Comparison of surface models derived by manual lidar and softcopy techniques
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Comparison of Surface Models Derived by Manual, LIDAR, and Softcopy Techniques. UW-Madison NCRST-I Research Team Frank Scarpace, Alan Vonderohe, Teresa Adams (Investigators) Nick Koncz (Project Manager) Hongwei Zhu, Amar Padmanabhan, Jisang Park (Research Assistants).

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Comparison of Surface Models Derived by Manual, LIDAR, and Softcopy Techniques

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Comparison of Surface Models Derived by Manual, LIDAR, and Softcopy Techniques

UW-Madison NCRST-I Research Team

  • Frank Scarpace, Alan Vonderohe, Teresa Adams (Investigators)

  • Nick Koncz (Project Manager)

  • Hongwei Zhu, Amar Padmanabhan, Jisang Park (Research Assistants)


Comparison of Surface Models Derived by Manual, LIDAR, and Softcopy Techniques

Objectives

  • Determine Differences among Results from the Various Techniques

  • Seek Methods for Improving Accuracies by Technology Integration

  • Seek Methods for Reducing Required Editing Time for Raw Softcopy Data


Test Site: Highway Corridor Near Solon, IA


Manual, LIDAR, and Softcopy Data Sets

  • Manual Photogrammetry Data Set Provided by Iowa DOT and CTRE:

    • Breaklines and Mass Points (~20-Meter Spacing)

    • Compiled on Analytical Stereoplotters from 1:4800 (nominal scale) photos

    • Expected Accuracy: 0.07-0.10m RMS


Breaklines and Mass Points


1-Meter DEM Generatedfrom Manual Photogrammetry Data Set


Manual, LIDAR, and Softcopy Data Sets

  • Softcopy Photogrammetry Data Set:

    • Same Photography as Manual Method

    • Same Camera Calibration

    • Same External Orientation Parameters

    • Film Diapositives Scanned at 15 Micrometers

    • 38 Photos in 3 Strips – 35 Stereo Models


Manual, LIDAR, and Softcopy Data Sets

  • Softcopy Photogrammetry Data Set:

    • In-House Software

    • Resampled Epipolar Images

    • 1:32 Image Pyramids

    • Cross-Correlation

    • Least Squares Matching

    • Generates Irregular 1-Meter Spacing of Elevations


Correlation Coefficients from a Single Model

Red = 0.5-0.7

Yellow = 0.7-0.9

Green = > 0.9


DEM by Softcopy Photogrammetry


Manual, LIDAR, and Softcopy Data Sets

  • LIDAR Data Set:

    • Irregular 2-Meter Spacing of Elevations

    • Expected Accuracy: 0.15m RMS

    • Raw Data Were Edited, But Some Vegetation (e.g., Crops) Were Not Removed


Part of the LIDAR Data Set


Parts of the Three Data Sets

Sample Comparisons and Results


Comparison Methodology


Sample Comparisons and Results

Preliminary Results Indicate that Softcopy Data are at Least as Good as LIDAR when Compared to Manually-Extracted Data.


Sample Comparisons and Results

Mixed Land Use


Sample Comparisons and Results

Drainage Ditch


Softcopy / LIDAR Integration Project Status

Softcopy Extraction w/LIDAR (Initial Comparison)


Softcopy / LIDAR Integration Project Status

Softcopy Extraction w/LIDAR (Initial Comparison)


Softcopy Editing Tools

  • Automated

    • Slope Filter (Spikes and Holes)

  • Manual (Stereo Viewing)

    • Point-by-Point

    • Polygon Constant Elevation

    • Polygon Planar Fit


Manual Editing Tool Menu


Manual Editing Polygon Selection Tool


Manual Editing Set-to-Constant Elevation Tool


One of the Stereo Pairs


Raw Softcopy Data


After Slope Filter


After Slope Filter


After Manual Editing


After Manual Editing


Effects of Slope Filter


Conclusions

  • When Differenced with Manually-Derived Data, Softcopy Results (0.2-0.4m RMS) are Slightly Better than LIDAR (0.3-0.5m RMS).

  • When LIDAR is Used as First Approximation for Softcopy, Results are Mixed with Improvements of 20% (to 0.16m RMS) in Some Cases.

  • Slope Filter Improves Raw Softcopy Data by 10%.

  • Comparisons with Manually-Edited Softcopy Remain to be Done.


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