an oblique-imagery case with pix4dmapper · 2015-10-28 · 3d textured mesh generated computed...
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An Oblique-imagery Case with Pix4Dmapper
Lisa Chen
Pix4D today
• Terrestrial / Aerial mapping
• 3D modeling
• Headquarters in Lausanne (CH)
• Pix4D Inc. San Francisco (USA)
• Office Shanghai (China)
• 50 employees
• More than 140 partners worldwide
• 8000+ active users
• 50+ projects on cloud every day
Various Sensors Supported
Case Information
Location: NashvilleNumber of Images: 596Ground Sampling Distance: 8 cmImage Acquisition Time: 15 minutesProcessing Time: 6 hoursNo Ground Control Points Used
Flight Plan
Patented Flight Plan
Manned Aircraft with Xcam-B Sensor Onboard
Sample Images from the Camera Rig
Pix4Dmapper Process
Finding Keypoints on Each Image Matching the Found Keypoints Among All the Images
Densified 3D Point Cloud Generate DSM and Orthomosaic
Initial Processing
Camera Rigs
The Camera Rig Used in the Project
The Camera Positions and 3D Point Cloud displayed in Pix4Dmapper rayCloud Interface
Camera RigsRelative Position of the Camera Rig
Indicates images from Camera Rigs in Pix4Dmapper
Camera Rig Calibration Interface Which Shows the Relatives and Corresponded Accuracy
rayCloud Editor
rayCloud in 3D is corresponded to the Original Images
Matched Points shown in Orange Circle
rayCloud
Two ray intersection has large error in the direction of the rays
rayCloud
Reduce the Error by intersecting from Multiview images
Error Ellipse (Ellipsoid)
Check the Accuracy of the Manual Tie Points by Viewing the Error Ellipse in rayCloud Editor Interface
Error Ellipse (Ellipsoid)
Check the Accuracy of the Manual Tie Points by Reviewing the Statistics on the Right and the Optimized Position on the Images
Point cloud and Mesh
3D Patches and NCC ScoreGenerate (by default) 7x7 3D patches from the feature points
Each records the point location and the norms
The 3D patches will describe the surface in more details
Image Pyramid
Multiscale: Image Pyramids ComputedLarge Objects may not be well defined by 3D (default) 7x7 patchesWith Multi Image Scale, Objects can then be well described
Dense Matching
The advantage of acquiring oblique imagery:
Assist both the initial and dense matching
Get more information on the façades which better defines the surfaces, especially for building corners
3D Textured Mesh Generated
Computed Triangle meshes and the textures The smoothness of the interpolation depends on the derivatives taken (C0 C1 C2)For oblique image cases, more triangles will provide sharper edges due to more content for the façades
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