PHOTOMOD Lite Project Contest

Transcription

1 PHOTOMOD Lite Project Contest Nomination: Education with PHOTOMOD Lite Institute name: Laboratory of Photogrammetry, School of Rural and Surveying Engineer, National Technical University of Athens Address: 9, Iroon Polytechniou GR Athens Contact Person: Andreas Georgopoulos, Sevasti Tapinaki e mail: drag@central.ntua.gr, sevi@survey.ntua.gr The Laboratory of Photogrammetry The Laboratory of Photogrammetry and the staff employed in it are part of the Department of Topography of the School of Rural & Surveying Engineers of the National Technical University of Athens. Photogrammetry in the Greek Universities is only lectured in the School of RSE of the NTUA and of the Aristotle University of Thessaloniki. NTUA's Laboratory of Photogrammetry assignment is, to fully educate and train the students on Photogrammetric issues, encouraging also relative research. At the same time, the Laboratory's infrastructure is constantly updated and improved, in order to serve its objectives in the above mentioned sectors. Research in the Laboratory of Photogrammetry, is carried out by the staff of the Department of Topography relative to the thematic area of Photogrammetry. It consists of research projects funded by various sources, of independent scientific research and of PhD Theses supervision and elaboration. The results of all that research activity, is presented in the publications of the members of the Laboratory. The Laboratory of Photogrammetry is aiming to "produce" new knowledge and to educate new theoretical and practical Photogrammetry researchers, through basic and applied research procedures. More specific, research issues are digital cartography and automations, measurements on simple images, large scale surveying, G.I.S. applications, etc. According to the UnderGraduate Studies Program of the SRSE NTUA the Laboratory of Photogrammetry is responsible for the education and training of the Faculty's students on the following areas, through courses and Master Theses attendance. The courses being taught by Laboratory members are: COURSE SEMESTER Photogrammetry I 5 Photogrammetry II 6 Photographic Data Acquisition 6 Photogrammetry III 7 Summer Photogrammetry Practice 8 Surveying and Documentation of Monuments 9 The Laboratory is also involved in the educational procedures of the post graduate programs "GeoInformatics" (SRSE NTUA), and "Monuments Protection" (School of Architecture). The last five (5) years the Laboratory is using PHOTOMOD for educational purposes in mainly three of these courses: Photogrammetry II, Summer Photogrammetry Practice and Surveying and Documentation of Monuments. The extensive use of the PHOTOMOD Lite version has given

2 the opportunity to use a digital photogrammetric system for the practice and training of many students at the same time. The students have the opportunity to exploit the availability of the Lite version in order to train at home. Course Photogrammetry II 6 th semester This course is being taught at the 6 th semester of the school and its aim is to educate and train the students on the following main areas: Methods for Aerial Triangulation (independent stereopairs and bundle adjustment) Digital Terrain Model production Orthophotography Satellite images and photogrammetry Lidar/SAR/Laser scanning At the same time the students have to elaborate and deliver exercises based on the theory where, some of them, are being elaborated using PHOTOMOD Lite. The duration of the course is 13 weeks with two two hour lectures per week. The necessary lectures for the theory of a certain area are followed by one lecture for the assignment of the exercise based on this theory. The website of the course is being constantly updated during the semester and contains the course material (lectures slides, exercises), announcements etc. During the 6 th semester of 2012 approximately 100 students attended in total 30 hours of lectures for theory and 18 hours for the assignment of the following exercises: Exercise 1 Exercise 2 and 3 Exercise 4 Exercise 5 Exercise 6 Exercise 7 Flight Planning Photogrammetric Orientations (Interior, Relative) using PHOTOMOD Lite Accuracies of stereo restitution Aerial Triangulation using PHOTOMOD Lite Stereoscopic drawing using PHOTOMOD Lite and anaglyph glasses Automatic creation of DTM and Orthorectification of images using PHOTOMOD Lite (Mosaic) The delivery date was set two weeks after the assignment of each exercise. For each exercise the students had to compose a technical report and deliver them, along with the products, to certain addresses, that were created especially for this purpose. The exercises were being corrected and the students received a reply mail with comments and corrections. For the exercises 2, 3, 5, 6 and 7, that where elaborated using PHOTOMOD Lite, the laboratory supplied the students with the following material: One strip flight with five (5) aerial images of the National Technical University Campus. (Figure 1) The calibration certificate of the camera (Table 1) A txt file with fifteen (15) ground control points coordinates in GGRS87 / Greek Grid coordinate system with coordinate accuracy 0.10m. (Table 2) A pdf file with the description and the exact position of the control points (Figure 2) Pdf files with instruction manual in Greek that was especially written for each exercise. The manual contains all the processing steps and tools of PHOTOMOD Lite that the

3 students had to use for the exercises and also all the parameters that they had to define. This material was based on the extensive and comprehensive on line manual, which comes with both the Lite and the Normal versions. The exe file for the installation of PHOTOMOD Lite The source aerial images were captured in August 1999 using the RMK TOP 15 with the parameters shown in Table 1 and they images were scanned using the Z/I PS1 photogrammetric scanner with pixel size 14μm namely 1800dpi image resolution. Table 1. Parameters of Source Aerial Images Scale of source images 1:6000 Calibration date 02/02/1999 Camera type Film X: mm Principal point Focal length mm Y: mm Distortion Radial Point of symmetry (zero distortion) To principal point Fiducial marks Fiducial coordinates R, mm dr, micron # X, mm Y, mm

4 Figure 1. The Block Scheme of the Strip Table 2. Coordinates of Ground Control Points Ground Control point X, m Y, m Z, m F TS F F TS F F F FS TS TS TS TS FS ANTLIOSTASIO

5 Figure 2. Example of the description of the ground control points. The lectures for the assignment of the exercises were given in the GeoInformatics Center (GC) that was established in March 1996 and is the focal point on Information Technology at the School of Rural and Surveying Engineers. The GC provides, among others, thirty four (34) Dell Studio XPS Intel I7 2.8 GHz, RAM 4GB, HD 500GB, VGA 512 MB ΑGP, DVD RW, Ethernet Gigabit, 18.5 TFT monitor and twenty five (25) Dell GX620 Intel PΙV 3 GHz, RAM 1GB, HD 80GB, VGA 128 MB ΑGP, DVD ROM, Ethernet Gigabit, 17 CRT monitor. The hardware used for the elaboration of the exercises was mainly the personal computers of GC, but also some student s personal computers and laptops, with unknown characteristics to us. The projector of GC was used for the presentation and the explanation of PHOTOMOD Lite. Figure 3. The GeoInformatics Center

6 Project workflow description Below is the description of the main processing steps followed for the elaboration of each exercise, as well as the used software modules and the parameters that were set. Also the output results are being described: Exercise 2 and 3: Photogrammetric Orientations (Interior, Relative) using PHOTOMOD Lite In these exercises the students were asked to create a new project each and to re establish the photogrammetric orientations (interior and relative). Each student delivered a technical report with the description of the theory that the exercises are based and the reports of each process, along with their evaluation and comments. Creation of new project (definition of name, coordinate system and project placement) Creation of new camera (definition of camera parameters) Import of images with the appropriate conversion Manual Interior Orientation Report on Interior Orientation (Threshold of residuals rms = mm) Check of the results and implementation of appropriate corrections Import of Ground Control Points (std. dev. X,Y,Z = 0.10m) Tie points measurements (including GCPs) Report on Relative orientation (Check vertical parallax DYmax = 0.014mm and Check residuals in triplets E Max XY = 0.020mm and E Max Z = 0.044mm) Check of the results and implementation of appropriate corrections Exercise 5: Aerial Triangulation using PHOTOMOD Lite The aim of this exercise was the students to understand aerial triangulation and compute the exterior orientation of the five images, using the measurements that they made in the previous exercises. The results should have the appropriate accuracy so that they could be used for the creation of an orthophotomap of scale 1:1000. Block adjustment with independent strips (acceptable residuals XYZ=1m) Check of the results and implementation of appropriate corrections Block adjustment with independent stereopairs (acceptable residuals XYZ=0.5m) Check of the results and implementation of appropriate corrections Final Block adjustment with bundle adjustment (image measurement precision 0.5pixel, GCP weight = 1 and acceptable residuals XYZ=0.1m) Check of the results and implementation of appropriate corrections Sigma_0 = Ground control point residuals N Xm-Xg Ym-Yg Zm-Zg Exy (metre) limit: mean absolute: * 0.108* RMS: * 0.128* maximum: 0.259* 0.206* 0.357* 0.307* number of points (differences): 15 ( ) Tie point residuals (on images) N x_pr-x_meas y_pr-y_meas Exy (mm) limit: mean absolute: RMS: maximum:

7 Exercise 6 Stereoscopic drawing using PHOTOMOD Lite and anaglyph glasses The laboratory gave each student a pair of anaglyph glasses, which they had to return after they have finished the exercises. In this exercise students had to select an area in one stereopair and draw in stereoscopic mode vector entities of their choice and classify them into appropriate layers. Creation of vector layer with classifier Determination of layers and codes for points, lines and polygons Open new 2D window Selection of stereopair Check of the anaglyph stereoscopic mode Activation of stereo Stereoscopic drawing of certain vector entities: points, lines and polygons (buildings, road network, trees, elevation points, contour lines etc.) Export vector entities to dxf file Exercise 7 Automatic creation of DTM and Orthorectification of images using PHOTOMOD Lite (Mosaic) In this exercise students were asked to create an orthophotomap of the area that they have chosen in scale of 1:1000. For this purpose they had to build one orthoimage of scale 1:1000 from each stereopair image. Compute points (pickets) automatically (Grid step XY = 5m and selection of certain area with the shift key, Correlator preset = rural area) In cases were the number of points exceeded the 50000, students had to increase the grid step or to select a smaller area. TIN creation using the points and the vector layer that was created in previous exercise as breaklines Correction of TIN (adding, deleting or moving points or lines)

8 DEM creation from TIN Opening of PHOTOMOD Mosaic module Determination of Mosaic Parameters (DEM and breaklines, cell size=0.10m, Resampling method=bilinear, Georeference file=arcworld TFW) Selection of source image (Remove/Add images from mosaic project) Build of orthoimage

9 In cases were the size of the output orthoimage file exceeded the 50MPixel the students had to increase the cell size Finally for the creation of the orthophotomap the students inserted the products of the exercises 6 and 7 (the dxf file with vector entities and the two orthoimages) in the AutoCAD. An example of the final product is shown in Figure 4

10 Figure 4. Sample of the final orthophotomap

11 Course Summer Photogrammetry Practice 8 th Semester The main objective of the course Summer Photogrammetry Practice is the familiarization of the students with the application of basic photogrammetric processes. The specific objectives of the course, which are equal to each other, are: I. The acquaintance with an integrated photogrammetric project II. The consolidation of theoretical knowledge on all subjects of the undergraduate curriculumnot only on the Photogrammetry by clarifying any obscure concepts III. The editing and production of final products During this course, which lasts 25 full time days usually in July, the students undertake to complete specific projects on photogrammetric issues, such as development of software for photogrammetric calculations, production of orthophotomaps, bibliographic research, etc. Especially for those students who chose to join the team that does part of the course at the archaeological site of Kimisala in Rhodes Island, the practice employs the integrated nature of a professional work. In this sense, the students are invited to experience all stages of a photogrammetric work, namely: planning of image acquisition, selection of place and marking of ground control points, data collection in the field, check and controls calculations photogrammetric processing and editing of final delivery Eleven (11) students attended the course that took place on July of The subject of the project was the production of the orthophotomap of a part of the road network of the destroyed ancient city of Vasilika in the archaeological site of Kimisala, in 1:50 scale. The source images were captured using the digital camera CANON MIII and a lens of focal length 24mm. The camera parameters are shown in Figure 5. The stereopairs had 70 80% overlap. Sample of source images is shown in Figure 8. The ground control points were measured with a total station and the coordinates were calculated in Cartesian Right (Local right Cartesian reference system) only oriented to the North of GGRS 87, with coordinates accuracy 0.01m (Figure 6).

12 Figure 5. Camera parameters CANON MIII 24 Figure 6. GCP list

13 For the needs of the shooting from a height of about 6 7m a special construction of tripod was used (Figure 7). Figure 7. The special construction of tripod In this project PHOTOMOD was used for close range photogrammetry. All the photogrammetric processing was made in PHOTOMOD Lite and the orthoimages with cell size of 0.005m were produced in PHOTOMOD Mosaic module. The necessary stereoscopic processing was made using anaglyph glasses.

14 The collection of DTM was made manually with a lot of breaklines and not so many individual points, because of the odd shapes and forms of the stones (Figure 8). Figure 8. Sample of the source images The final orthophotomap was created in AutoCAD (Figure 9)

15 Figure 9. The orthophotomap of part of the road network of the ancient city Vasilika

16 Course project Surveying and Documentation of Monuments 9 th Semester This course project is being taught at the 9 th semester of the curriculum and its aim is to educate and train the students on the Geometric documentation of monuments with topographic and photogrammetric methods. The goals of this course project are A. Integration of the already gained knowledge (geodesy, Photogrammetry, least squares method etc.) B. Supplementation with new knowledge C. Raising awareness on cultural Heritage issues D. Practical application During the semester there are lectures for theory relating to: History of Architecture Reading of monument Digitalization of Cultural Heritage Accuracy networks, Monitoring of deformation and micromovements Collection of 3D data Products of Geometric Documentation (specificities, demands, 2D 3D, differentiation from conventional products) Information Systems of Monuments etc. At the same time students have to deliver certain products for a certain monument, usually in Athens. During 2012 ten 10 students attended this course and the monument that they documented was the Temple of Hephaestus. The Temple of Hephaestus (also called Thissio) is one of the most preserved ancient Greek temples of space. It was dedicated to the god Hephaestus and Athena Ergani. Located in the area of Theseus, this got its name because of the old, now revised version of the temple to Theseus. The Temple of Hephaestus is accessible to the public as part of the archaeological site of Ancient Agora. Figure 10. The south façade of the Temple of Hephaestus (Thissio)

17 The products that the students were asked to deliver were: one horizontal section at a level of 1.1m above the main floor at a scale 1:50 one vertical section that shows the main entrance at a scale 1:50 and a part of the south façade at a scale 1:50 The two sections were measured with a total station and produced only vector drawings. The façade had to be a raster and vector drawing so it was decided to use photogrammetric methods and finally produce orthoimages using the PHOTOMOD Lite. In this project PHOTOMOD was used for close range photogrammetry. The students trained on how to: Plan the image acquisition for the stereopairs, Mark the ground control points and measure them with a total station, Calibrate the camera Perform the photography themselves Use the PHOTOMOD Lite for the photogrammetric orientations and the production of orthoimages. The fieldworks lasted two days while the office work lasted four weeks, considering the educational nature of the project, till the final delivery of the drawing of the south façade of the Temple. The source images were captured using the digital camera CANON MIII and a lens with focal length 24mm. The same camera set with the previous mentioned course. Finally two strips were made with approximately 70% overlap: one for the upper part of the Temple containing the columns and the top part consisting of 15 images and one for the stairs of the Temple, consisting of 16 images (Figure 11) Figure 11. The Block Scheme of the second Strip

18 The collection of DTM was made manually and because of the strong anaglyph of the object, considering the large scale of the images, strange and wrong triangles were created in the TIN. The problems with the strange triangles were solved with the decision to create separate TINs for several elevations. Finally, five elevations were defined such as the three elevations of the stairs, one elevation for the columns and one for the wall of the Temple (Figure 12 & Error! Reference source not found.) Figure 12. Sample of source images and the five elevations Figure 13. DTM for the three elevations of the stairs

19 The produced orthoimages were imported in AutoCAD were the final drawing was produced. (Figure 14) Photomod software is also extensively used in Diploma theses (i.e. Master s theses) when they are concerned with the production of photogrammetric products, such as vector drawings or orthophotomaps. It is evident that within the curriculum of the School of Rural & Surveying Engineering full exploitation of the Photomod software is being made. Especially the availability of the Lite version gives the opportunity to all students to gain real hands on experience to a Digital Photogrammetric Workstation. In this way they are fully equipped to confront any photogrammetric project in their professional life after graduation.

20 Figure 14. The drawing of the South façade of the Temple of Hephaestus