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++Analysis of UAS data processing results +
++GIS/MEA 584: +
++Mapping and Modeling Using UAS +
++Justyna Jeziorska +
+
+Center for Geospatial Analytics
North Carolina State University
+
+Objectives +
+-
+
- +Understand how to interpret a processing report + +
- +Compare errors and survey data from different flights + +
- +Recognize differences in geoprocessing products generated by different software + +
- +Understand significance of using GCPs in the processing and their impact on the final products + +
- +Recognize what processing steps need to be modified in order to improve particular errors + +
- +Understand what causes the ‘Bolw effect’ and know the solutions to fix it. + +
- +Execute simple terrain measurements in Agisoft Photoscan + +
+Flights Oct. 6th 2015 +
+
++Flight Feb. 6th 2018 +
+
++Flights Oct. 6th 2015 +
+
++Analyzing the processing report +
+
+
+ <img src="img/Agisoft_report.png"width ="90%">
+
++Includes: +
+<ul>
+<li class="small fragment">Orthophoto and digital elevation model sketch;</li>
+<li class="small fragment">Camera parameters and survey scheme</li>
+<li class="small fragment">Tie points data export (matching points and panoramas) </li>
+<li class="small fragment">Image overlap statistics</li>
+<li class="small fragment">Camera positioning error estimates</li>
+<li class="small fragment">Ground control point error estimates</li>
+</ul> +Orthophoto +
+
++Survey data +
+
++Flight plans +
+
++Flight plan – flight 1 +
+
++Flight plan – flight 2 +
+
++Ground Control Points +
+
++Ground Control Points +
+
++Camera calibration report +
+
++Camera calibration report +
+
++Camera calibration report +
+
++Camera calibration report +
+
++Camera calibration report +
+
++Camera calibration report +
+
++Camera calibration report +
+
++Analyzing the processing report +
+
+
+ <img src="img/camera_calibration_report.png">
+
+<ul>
+<li class="fragment">While carrying out photo alignment PhotoScan estimates both internal and external camera orientation parameters, including nonlinear radial distortions.</li>+Tools > Camera calibration +
++Image residuals +
+
++Image residuals +
+
++Image residuals +
+
++Image residuals +
+<pclass=“fragment”>The geometric error corresponding to the average image distance, measured in pixels, between: + +
++Image residuals +
++This reprojection error is equivalent to the root mean square (RMS) image residuals used in photogrammetric literature +
++More on image residuals in this article +
+
++Flight path +
+
++Flight path in 3D +
+
++Digital Surface Model +
+
++Digital Surface Model +
+
++DSMs comparison +
+
+
+difference [m] between DSMs generated
based on data from two consecutive flights
+
+DSMs comparison by software +
+
++DSMs comparison -GCPs +
+
++‘Bowl effect’ +
++effect can be introduced during photo alignment, in case camera calibration estimates are inaccurate +
+
++‘Bowl effect’ +
++effect can be introduced during photo alignment, in case camera calibration estimates are inaccurate +
+
++‘Bowl effect’- solutions to the problem +
+-
+
- +If camera calibration is known in advance- it can be loaded in PhotoScan and fixed during photo alignment. + +
- +Optimization procedure - recommended approach + +
<ul>
+ <li class="fragment">based on <strong>camera</strong> or <strong>GCP</strong> coordinates</li>
+ <li class="fragment">performed after photo alignment</li>
+ <li class="fragment">is recommended to perform optimization based on ground control data in any case, even if precalibrated cameras are used</li>
+ </ul>
+</ol>+Optimization +
+
++What is an optimization? +
+ <ul>
+ <li class="fragment">PhotoScan performs full photogrammetric adjustment taking into account additional constraints introduced by ground control data</li>
+ <li class="fragment">Extrinsic and intrinsic parameters for all cameras are optimized at this step, in contrast to the simple 7-parameter transform used for georeferencing by default</li>
+ <li class="fragment">Optimization helps to significantly improve accuracy of the final solution</li>
+ </ul>+More on the bowl effect in this article +
++Software related issues +
++Pix4D - Trimble, Agisoft - Trimble +
+
++artifacts on Trimble DSM - “tiles” pattern visible for both cases +
++Measurements in Agisoft Photoscan +
+-
+
- +Agisoft has capability of performing simple measurements on DSM and 3D model: + +
- +Profile generation + +
++Measurements in Agisoft Photoscan +
+-
+
- +Generating contour lines + +
++Measurements in Agisoft Photoscan +
+-
+
- +Volume and area measurements + +
++Terrain analysis in GRASS GIS +
++computing aspect, slope +
+
+Terrain analysis in GRASS GIS +
++computing curvature and shaded relief maps +
+
++Advanced terrain analysis +
++computing local relief, skyview +
+
++What did we learn? +
+-
+
- +What are the imagery processing outputs +
- +How to interpret the processing results based on processing report +
- +How to compare results of differing processing results (by software and GCPs used) +
- +How use Agisoft Photoscan for simple measurements +
- +What GIS tools can be used for more advanced terrain analysis +