1. VIIth International Scientific and Technical Conference From Imagery to Map: Digital Photogrammetric Technologies ADS40 imagery processing using PHOTOMOD: technology and experience Petr S. Titarov, Software Developer September 17-20, 2007, Nessebar, Bulgaria

2. Report outline ADS 40 image acquisition ADS 40 image acquisition Software involved and data flows Software involved and data flows Solving space intersection and resection problems Solving space intersection and resection problems Processing ADS40 using PHOTOMOD Processing ADS40 using PHOTOMOD Pilot project: creating 1 : 2 000 orthoimagery Pilot project: creating 1 : 2 000 orthoimagery

3. ADS 40 image acquisition

4. ADS 40 Level 0 imagery X Y Z    Exterior orientation Level 0 image ADS40 Level 0 images are distorted due to pushbroom imaging mode and exterior orientation instability.

5. ADS 40 Level 1 imagery creating The Level 1 image is generated by projecting Level 0 image onto the constant height plane in the Local Space Rectangular (LSR) reference frame using in-flight (not adjusted) exterior orientation.

6. Level 0 vs. Level 1 Level 0 image Level 1 image As compared with Level 0 images, the Level 1 images are non-distorted, comfortably viewable, suitable for automatic tie points measurement.

7. Specific aerial pushbroom imagery artifacts On the edge of the image Inside the image The gaps on the ADS40 Level 1 images are caused by abrupt exterior orientation change. Level 1 images edges AN-30 L-410

8. Data flows between software involved GPro Level 0 imagery creation, automatic tie points measurement Level 1 imagery creation ORIMA Block adjustment PHOTOMOD DTM/DEM extraction, 2D/3D vectorization, orthoimagery creation Adjusted exterior orientation (*.odf.adj) In - flight exterior orientation (*.odf) Sensor calibration (*.cam) Ground control and tie points Level 1 imagery + metadata (*.sup) + sensor geometric calibration (*.cam) + in-flight exterior orientation (*.odf)

9. GPS/IMU software, GPro, ORIMA… GPS/IMU software GPro ORIMA Post-processing of the in-flight GPS/IMU measurements: POSProc/ POSGPS POSProc/ POSGPS GrafNav GrafNav Image download from on-board storage, Level 0/1 imagery generation ADS 40 block adjustment

10. PHOTOMOD Software PHOTOMOD DTM DTM derivation PHOTOMOD StereoDraw PHOTOMOD Mosaic PHOTOMOD Vector 3D Vectorization Orthomosaic generating Digital map creating

11. Space intersection and space resection problems Space intersection Space resection Space intersection is solved to derive DTM. Space resection is solved to create orthoimagery.

12. Solving space resection problem by Level 1 image Level 1 space resection solving scheme Level 0 space resection Solving Level 0 space resection problem is time-consuming operation due to pushbroom image acquisition mode and the instability of the airborne sensor exterior orientation. The procedure consists of three stages: Iterative contracting the search area (estimating line and detector number ranges); Iterative contracting the search area (estimating line and detector number ranges); Sequential line number search throughout the range; Sequential line number search throughout the range; Calculating detector number using line number found; Calculating detector number using line number found;

13. Solving space intersection problem by Level 1 stereopair Level 1 space intersection solving scheme

14. Selecting images for processing in PHOTOMOD Stereo processing Orthoimagery creating 14 ̊ backward + 28 ̊ forward 14 ̊ backward + nadir nadir + 28 ̊ forward B : H = 0.25 B : H = 0.78 B : H = 0.53 Best correlation, but worst stereo precision Best stereo precision, but worst correlation Orthoimagery should be created using nadir images to minimize the influence of DTM errors on the orthoimage accuracy.

15. PHOTOMOD project structure for ADS 40 processing Since the block adjustment of ADS 40 data is performed by ORIMA, there is no reason to insert the entire block into single PHOTOMOD project. Project structure in the case of stereopair composed of nadir and off-nadir images Project structure in the case of stereopair composed of backward and forward images: the nadir image is added into separate strip. The orthomosaic is created using capability of PHOTOMOD Mosaic module to involve images from several PHOTOMOD projects.

16. Adding ADS 40 images into the PHOTOMOD project Radiometric enhancement Automated folder analysis and data search

17. Focus on reference systems The exterior orientation is given with respect to LSR (Local Space Rectangular) reference system. So the connection between PHOTOMOD project reference system and LSR should be provided. There are two ways to establish the connection: To measure at least three points with known ground coordinates on the stereopair (shift – rotation – scale seven parameters set will be calculated); To measure at least three points with known ground coordinates on the stereopair (shift – rotation – scale seven parameters set will be calculated); To specify completely the PHOTOMOD project reference system - datum, map projection etc. To specify completely the PHOTOMOD project reference system - datum, map projection etc. Local Space Rectangular PHOTOMOD project reference system

18. Pilot project: 1 : 2000 orthoimagery production scale: 1 : 2 000 scale: 1 : 2 000 sheets number: 351 sheets number: 351 orthoimagery area: 91,25 km 2 orthoimagery area: 91,25 km 2 14 ̊ backward + nadir stereopairs were used to derive DEM for orthoimagery creating Source data images GSD: 20 cm images GSD: 20 cm strips number: 24 strips number: 24 data (L0&L1) volume: 0.5 Tb data (L0&L1) volume: 0.5 Tb Output orthoimagery

19. Pilot project: workflow GPS/IMU post-processing GPro ORIMA PHOTOMOD DTM PHOTOMOD Montage Desktop PHOTOMOD AT PHOTOMOD Mosaic In-flight exterior orientation data preparation Level 1 imagery generating Block adjustment PHOTOMOD projects creating DTM extraction from stereopairs Deriving orthomosaic using images and DEMs from several PHOTOMOD projects STEP BY STEPSTEP BY STEPSTEP BY STEPSTEP BY STEP

20. Pilot project: check points points number : 15 points number : 15 strips number: 24 strips number: 24 images GSD: 20 cm images GSD: 20 cm X,Y mean errors:  20 cm X,Y mean errors:  20 cm Z mean error:  30 cm Z mean error:  30 cm

21. Pilot project: orthoimagery samples PanchromaticColor

22. Thank you for your attention! THE END