Photogrammetry

Photogrammetry

From Classical to Digital to Laser Scanners

Dr. Ghadi Younis - Zakarneh College of Engineering Civil & Architectural Eng. Dept. The 4th Annual Conference for Engineering and Surveying in Palestine (Cadastral Surveying & Reference Networks) Ramallah- Palestine 19.Sept.2017

Photogrammetry Basics  Flying height (H) , focal length (f) , topography (h)  scale = f/(H-h)

Project : strips , endlap (60%) , sidelap (20%)

3D/Stereoscopic vision

3D Mapping (stereoplotting)

Analog stereoplotter (optical mechanical Systems)  Limitations : number of photos , no continuity , efforts , time of

mapping …. etc

Analytical stereoplotter (Computer assisted system) 80s+90s  Manual measurement + mathmatical solutions + digital output map (CAD)

Analog + Analytical Photogrammetry Mapping Concepts  Photo scale = f/H  Map scale = (f/H )* Zoom factor (optical system)  Common zoom factors 5-7 (commonly used 6 ( ASPRS)  C-factor= H/(CI)  C-factor : general description of height accurcy factors for contour Intervals

(CI) :nature of the terrain, the camera and its calibration, the resolution quality of the photography, the density and accuracy of the ground control, and the capability of the plotter operator . (common 1200-2200) professional stereoplotters have c-factor of 2000)

 For 9” /23cm film format + 6”/152.4mm camera

Softcopy Workstations  1990s … Scanned film/Photo based + Softcopy Operations

+ Digital Map output + Ortho +DTM/DEM

Softcopy mapping concepts  Scan Resolution (Micron )  Photo scale  Ground Sampling Distance (GSD)  Common scan resolution 21 micron + zoom factor of 6 …For 9”

/23cm film format + 6”/152.4mm camera + c-factor 1800

Digital Workstation  CCD Digital Camera + SoftCopy workstation + Digital

output  Digital Cameral : focal length , CCD pixel size (micron) + #of pixels , panchromatic/RGB/Multiband

Digital Photogrammetric Capabilities             

Image enhancement / Image Resambling Vertical/tilted/oblique image orientations Camera calibration Professional /mature + metric/non-metric cameras Aerial/terrestrial /close range photos/applications Aerotriangulation Automatic Point/Feature Matching Automatic orientation 3D Vision Manual/Automatic DEM/DTM creation and processing Digital Orthoimage creation / mosaicing 3D cloud production and procession ….. Much more

Mapping concepts  Photo scale : Photo Pixel Size  Photo GSD  Map Scale , C-factor 1800 , zoom of 6

are outdated

 Accuracy measures in xy or Z are measured using chech

points and RMSE. (ASPRS accuracy sttandards, 2014)

Control Points and Check Points

Drone and UAV (Unmanned Aerial Vichele)  Easy flight control unsing smart phone or tablet , fast

photography small areas , professional cameras , GNSS/GPS –INS systems  Easy processing Software , accurate 3D modeling for topography buildings and construction

Mobile Mapping Imaging Systems e.g Trimble MX7  fast and cost effective  Rapid 360-degree geo-referenced image documentation  Precision positioning using GNSS and inertial referencing system  Deploys on all sizes of vehicles  Direct 3D viewing/measurement/modelling Software

Laser Scaning (Aerial) / LIDAR

Terrestrial Laser Sacanners e.g Trimble TX5 , TX8

3D grid point XYZ + color RGB

Trimble TX5 @ PPU

Recommendations  In addition to GNSS and Total Stations other tools like

Drone/UAV , laser scanners can be used for land surveying due to low cost and ease of use compared to classical photogrammetry  Direct XYZ with real world info Can be achieved using these tool. Quality control and check of field work can be easly in office applied.  3d Mapping / cadastral systems should be studied to applied , E.g apartment registration  Quality control related using check

points should be officially

documented in procedures in photogrammetric and cadastral works.

Thank You