Journal of Convergence Information Technology

Journal of Convergence Information Technology Volume 5, Number 1, February 2010

Building 3D Geospatial Information using Airborne Multi-Looking Digital Camera System Hyung Tae Kim*1, Sang Bong Kim*2, Jong Sik Go*3, Yang Dam Eo*4, Byoung Kil Lee*5 *1 Korea Land & Housing Corporation, Seongnam, Korea *2, Corresponding author, 3 Chung-Ang Aerosurvey co., Ltd., Seoul, Korea *4 Dept. of Advanced Fusion Technology, Konkuk University, Seoul, Korea *5 Dept. Of Civil Engineering, Kyonggi University, Suwon, Korea [email protected], [email protected], [email protected], [email protected], [email protected] doi: 10.4156/jcit.vol5.issue1.2

Abstract

As of 2009 in Korea, total 728 projects of 36 government, government agencies and local governments have been carried out from 1996 according to the NGIS(National GIS) master plan [3].

3D geospatial information is information which presents the real world, and contributes to quantitative analysis and decision making support of construction, forestry, disaster management etc. using integrated orthophoto, DEM, attribute data, 3D modeling and visualizing information. Multi-looking Aerial photogrammetric method, which is more efficient than traditional one, can save the expenditure of public sector and increase their efficiency, and can be applied to diverse applications of private sector. It is expected to be a one of the valuable national projects in time.

Table 1. Projects related to the spatial information (Report on Spatial Information Projects) No. of Organizations

No. of Projects

Government and government agencies

20

96

Keywords

Local government

16

632

3D Geospatial Information, Orthophoto, DEM, 3D Modeling, MLDCS (Multi-Looking Digital Camera System)

Total

36

728

Korean government had carried out the NGIS support research (3D geospatial information construction plan) for 3D geospatial information construction project among the above-mentioned projects from 2002 to 2003, and the pilot had been executed at Daejun metropolitan area from 2004 to 2005. In pilot projects, DEM(Digital Elevation Model), orthophoto and 3D geospatial information of 20 cities had been constructed from 2004 to 2008 [3]. shows project areas.

1. Introduction 3D geospatial Information is information that represents the real world adding height, color, texture and attribute to 2D topographic information. In other words, this is a digital map of cubic representation which is made from 2D digital maps, topographic surveying results with height and aerial photographs [1], [17]. To renovate efficiency and service of government, 3D spatial information of major cities of Korea has been prepared from 2006 by NGII (National Geographic Information Institute) [2]. However, there are many discussions on more accurate, efficient and effective production method of 3D information, because of the increasing interests in application of information and needs for high quality geographic information services [1], [4].

Table 2. Budgets of 3D geospatial information construction projects (unit :million Korean Won) 2004 2005 2006 2007 2008

3D Geospatial Information Construction

15

2,500

2,500

2,100

2,500

2,500

Building 3D Geospatial Information using Airborne Multi-Looking Digital Camera System Hyung Tae Kim, Sang Bong Kim, Jong Sik Go, Yang Dam Eo, Byoung Kil Lee Looking Digital Camera System are recommended to use. These techniques make it possible to build real world like spatial information by constructing the DEM, high resolution digital orthophoto and multilooking oblique images at a time. 3D geospatial information construction methods are compared, and the alternatives are proposed to build more similar 3D virtual space information to the real world.

Table 3. Pilot projects of 3D spatial information construction (Korea)

Project Areas

Total 2004

2005

2006

2007

2008

Seogu, Deajun

Junggu and Seogu, Daejun

6 Cities including Uiwangsi

6 Cities including Inchon-si

8 Cities including Guri-si

20

2. General Concept of 3D Geospatial Information Construction

According to the law, construction methods, procedures and standards of 3D geospatial information was defined at Dec., 2008, and MLTM (Ministry of

3D geospatial information consists of spatial information and visualizing information. Spatial information construction contains raw data processing and DB construction per layer. LiDAR, digital camera and ground control surveying are raw data processing and 3D transportation data, building data, hydrographic data and topographic data are DB construction by layer. Contents of visualizing information include producing of mono, color, virtual and photographic image textures [5]. 3D geospatial information is constructed by integrating the results of manipulated various raw data. Raw data come from digital map, LiDAR, mobile mapping system, multi-looking digital camera system, aerial photo and so on. Especially for efficient 3D geospatial information construction manipulating and using existing data, using related techniques and relating with other systems should be considered.

shows the procedures of 3D geospatial information construction. Also,

shows technologies with stability and related regulations in 3D geospatial information construction.

Land, Transportation and Maritime) legislate 「Guide on Spatial Information Construction Management」. NGI legislate 「Regulations for Aerial laser mapping Operation」(2009. 1. 6) and 「Regulations for 3D Spatial Information Operation」(2009. 5. 8) which are the basis of 3D geospatial information construction, also. Popularity of Google Earth and continuous interests in their own country prove the needs and markets of 3D spatial information [18]. So each country develops and researches technology at various public and private sector for constructing its own 3D national spatial information. For example, in U.S. National Map plan was established at 2001 to build consistent and integrated spatial data infrastructure, then the 3D spatial information is up-to-date via continuous update of spatial information, nationwide. OS (Ordnance Survey) of Britain provides various kinds of spatial information. They expect that Master map, which is developed for electronic commerce and mobile market, is going to take a main role to manage and use of the geographic information, in near future. Canada drives CGDI (Canadian Geographic Data Infrastructure), Centre for Topographic Information, government agency under NRCAN, provides, manages and updates various data for 3D GIS [1]. Japan had driven researches in information and communication technology for GIS construction, research of basic technology for 3D GIS construction and spread of 3D GIS, then researches information and communication technology for practical 3D GIS. Based on foreign examples, construction of 3D geospatial information is based on the basic geographic data, such as digital map, satellite images and aerial orthophoto as well as DEM. And researches are focused on the completed 3D spatial information technology like Master Map of Britain. In this paper, latest 3D geospatial information building techniques such as LiDAR (Light Detection and Ranging), GPS/INS, digital camera, Multi-

Table 4. Technologies for 3D Geospatial Information Construction Items DEM construction Aerial photograph

Technology • Aerial laser mapping with aerial LiDAR • Large format digital camera for photogrammetry

3D modeling and visualizing

• Aerial photogrammetry

information Orthophoto

16

• Ortho rectification

Journal of Convergence Information Technology Volume 5, Number 1, February 2010

Figure 1. Procedures of 3D Spatial Information Construction

3. Data sources and Construction methods

Eq. (2) : phase difference, f: frequency, R: (here, distance, c: velocity of light.)

3.1 Digital Aerial Photograph Compared to analog camera, digital camera proved that geometric image quality is excellent and the efficiency is very high. Especially the image quality is rated during taking the picture, so the quality is proved and get the data as soon as people take the picture. Time and other expense can be reduced because of that. Therefore digital camera is generalized in building 3D spatial information recently [6],[19]. In aerial photogrammetry, shooting (or taking a picture) is very important part and it is the most basic step, which affects every following steps and precision. Therefore aerial photographing needs detailed planning about flight, camera operation, photographing technique and developing images, and aerial photograph is taken at proper weather condition [7].

With pulse, LiDAR measures round trip time ( ) and distance using higher energy than CW laser (see Eq.(3), (4)). Eq. (3) Eq. (4) For the present, aerial laser mapping systems usually use pulse system. Aerial laser mapping system produces precision DEM by gathering 3 dimensional information of high resolution irregular point for earth’s surface and its reflectance in digital form.

shows the procedures of aerial laser mapping and it is divided in three parts. First step is convert aerial laser scanning data into 3D data, here position and attitude of laser sensor are determined by IMU (Inertial Measurement Unit), GPS, and point data with horizontal coordinate and vertical height are derived from post-processing. Second step contains converting the height of point data from ellipsoidal height to normal height, checking the errors, eliminating noises, and classifying points into earth surface, building and forest with filtering. Then, at last point data is interpolated to rasterized DEM and DSM (Digital Surface Model) [8].

3.2 LiDAR DEM Principles of ranging with laser is using pulse and using phase difference. With phase difference, LiDAR measures round trip time ( ) and distance using CW(continuous wave) laser system which emit continuous light [20] (see Eq.(1), (2)). Eq. (1)

17

Building 3D Geospatial Information using Airborne Multi-Looking Digital Camera System Hyung Tae Kim, Sang Bong Kim, Jong Sik Go, Yang Dam Eo, Byoung Kil Lee projection center, rotation matrix.)

: coefficients of

shows the procedures of orthophoto generation from aerial digital image. Orthophoto generation of aerial photo, which differs from existing method in pre-processing step, performs raw data download and GPS/INS processing and needs minimum 5 GCPs (Ground Control Point) with horizontal and vertical coordinate over project area. Image control is surveyed by bundle adjustment using lots of automatic tie-points and GCP, DEM is generated using image matching, digital map and LiDAR data [16]. True orthophoto is produced by ortho rectification, which removes relief displacement of topography and building, using image control point, DEM and 3D building data. True orthophoto is final product after mosaic and color correction [10].

Figure 2. Procedures of Aerial Laser Mapping Aerial laser mapping data is used as basic information for adding the height to building in construction of 3D city model. In legacy city model 2D building polygons are extruded to the building height. By adopting LiDAR, not only simple building model but also minute structures in rooftop can be modeled, precision and automation of 3D surface model is improved dramatically. By this reason large amount of 3D city model can be produced effectively [9].

3.3 Orthophoto General aerial photo cannot depict accurate position, because of inclination of sensor and relief displacement, but orthophoto can be used as a map to locate and measure something [21]. Orthophoto is produced by differential rectification using DEM and collinearity condition. Especially to determine DN (digital number) of image (grey/color level) of Orthophoto, image coordinate (x, y) is derived from 3D coordinate (X, Y, Z) of each of DEM cell using collinearity equation, then corresponding DN is determined using one of the image resampling method (such as nearest neighborhood).

Figure 3. Procedures of Orthophoto Generation

Eq. (5)

Eq. (6) (here, : image coordinate of point i, : coordinate of principal point in image coordinate system, : 3D coordinate of DEM cell correspond to , : 3D coordinate of

Figure 4. True Orthophoto In orthophoto generation, occlusion and duplicated mapping problems occur because of sky-scrapers in

18

Journal of Convergence Information Technology Volume 5, Number 1, February 2010 city [12], but high overlap and precise 3D building data can solve the problems to produce high quality orthophoto (see

).

photo for rooftop of objects and terrestrial photo or virtual image for building façade.

shows procedures of existing method for 3D modeling and visualizing information construction. Using this method, objects is determined by year of digital map, so it is hard to reflect real world contemporarily and the area which has changed in topography can’t have 3D object with uniform quality.

3.4 Attribute Information Attribute data is constructed with transportation, building and hydrographic data, reference to digital map and address data. In case of necessity, data is modified by field survey [5]. Fields and values of attribute information should be compliant to the “Definition of 3D Spatial Information Data Model” of NGI.

shows modification procedures of attribute data by field survey, when inaccurate data is detected because of out-dated or omission of existing data

Figure 6. Procedures of Existing Method for 3D Modeling and Visualizing Information Construction 2) Multi-looking Aerial Photogrammetric Method The latest adopted Multi-looking oblique digital camera system get five images; four photos are oblique (East, West, South, North) and one photo is nadir. If overlap reaches over 60%, it produces total 12 images and minimizes occluded area, especially with 40° oblique images, it offers high quality visualizing information [11]. Unlike nadir image, in orthophoto generation, relative rotation of camera to INS and separation from GPS should be considered to formulate relationships between image and terrestrial coordinate system (See Eq. (7)).

Figure 5. Modification Procedures of Attribute Data

4. 3D Modeling by Multi-looking Airborne Images 3D modeling and visualizing information construction use 3D plotting method using stereo aerial photograph or manual method using existing digital map and aerial laser mapping data. Considering accuracy, budget and time, 3D spatial information is constructed from digital map and aerial laser mapping data adding the real image textures of terrestrial photo, till now. But, introducing the multi-looking digital camera system, it is expected that the quality of 3D spatial information and its usability are increased by aerial photogrammetric technology.

Eq. (7) : image coordinate, : corrections (here, for principal point, : focal length, : scale factor, : rotation of INS to reference coordinate system, : rotation of boresight, : ground coordinate, : GPS position, : separation , between GPS and INS, , : separation between INS and camera lens.)

1) Existing Method 3D spatial information construction uses existing 1/1000 digital map for horizontal accuracy and aerial laser mapping data for vertical accuracy. Visualizing data uses aerial

19

Building 3D Geospatial Information using Airborne Multi-Looking Digital Camera System Hyung Tae Kim, Sang Bong Kim, Jong Sik Go, Yang Dam Eo, Byoung Kil Lee The formula can be reduced to Eq. (8).

mapped with real image textures of façade of buildings [15]. At this time, most optimal image is selected using geometric information of exposure time and 3D modeling information.

shows diagrammatic procedures of 3D visualizing information construction.

Eq. (8)

This equation is same as normal collinearity condition. Even though Multi-Looking digital camera system has fixed relative position of image by direct georeferencing using GPS/INS, but to construct high quality 3D spatial information, accurate external orientation parameters should be determined by tie-point and GCP surveying. Here, tie-points should be evenly distributed like

considering separations between image points and characteristics of oblique images. Besides, all the images corresponding to the tie-points and GCP should be observed, and more than 3 images are recommended.

Multi-looking Images (Oblique, Nadir)

3D Modeling Data

Mapping Visualizing Data

Figure 9. 3D Visualizing Data Construction

5. Benefits from 3D Geospatial Information 3D geospatial information is constructed over whole country considering present and changes of future, applying these information to cadastre, underground facilities, buildings and etc. anyone who wants information can use 3D geospatial information anywhere and anytime. Using 3D geospatial information, government can cut the national budget and activate spatial information industry. Eventually it is expected that Korean government can achieve the effective use of resources, creating the ubiquitous business and minimizing the damage from disasters using 3D analysis, and contribute to “realizing the cyber nation administration and originating the IT convergence cutting-edge industry” [1].

Figure 7. Allocation of Tie-points

shows that 3D modeling data is extracted from oblique and nadir images by portrait without stereo plotter [14]. It means that 3D modeling data is constructed using horizontal position(X, Y) from nadir image, height(Z) from oblique image and high resolution DEM (cell size 1m). Compared to existing method, state-of-the-art photogrammetric method does not need experts and improves operation speed, so effective 3D modeling is expected.

5.1 Tangible Benefit If 3D geospatial Information is updated regular using state-of-the-art aerial photogrammetric method, a lot of budget can be cut by substituting this information for other fragmented spatial information construction projects or some of its process. And it is expected that the quality of national spatial information can be upgraded by periodical update of spatial information, such as digital map [1].

Figure 8. 3D Modeling Data Construction Using 3D modeling data and geometric information of images, visualizing information is automatically

20

Journal of Convergence Information Technology Volume 5, Number 1, February 2010

Sum of the expected cost of spatial information construction, operation, maintenance, application development of the relevant government ministries and investment in private sector for 13 years from now are contained in current value of cost. And, optimization of business and budget savings are contained in current value of benefit.

services, contents, education, games, etc., makes legacy industries low-carbonize and lead carbon-free new industries. As the demand of the nation for information services, geographic information should be opened and circulated, and the potential of 3D geospatial information and a ripple effect on private economy is expected. Hereafter, 3D geospatial information construction project images Korea as a whole, and fulfill the customers demand with easy and realistic geographic information. DEM, 3D topographic data, for whole country will be used for design survey of civil construction, forestry, environment, disaster management, policy establishment, etc., and 3D information of urban facilities for major Korean cities will be applied a lot to landscape deliberation, decision support, urban environmental planning, urban rehabilitation, urban management, urban planning, real estate work, and so on. Especially, considering the demand of private sector and economical・industrial aspect, 3D national spatial information construction project is requisite for technical development and overall expansion of GIS industry.

5.2 Intangible Benefit

6. Conclusion

In Korea various types of spatial information is generated and constructed by 1st and 2nd NGIS projects, but most of the outputs of NGIS project including digital map are 2D-based information. The outputs of NGIS became the infra data for vitalizing the GIS industry, then they are applied for presentation of national land space and application technology. But, 2D data cannot properly represent the real world phenomena in 3D space, because of its limits. Computer hardware and software developed rapidly lately, users, who want spatial information by GIS, require 3D spatial information with reality rather than 2D data with abstracted reality. Therefore, by performing the 3D geospatial information project, realistic image information and 3D land, which are formed basis of national spatial information infrastructure, can be represented. And, the outputs can be used as fundamental data for administration, such as cadastre, urban planning, environment, construction, disaster management, using 3D geospatial information by constructing and maintaining various theme of spatial information (e.g. cadastral map, ecological map, road network, etc.). It will support the scientific decision making for numerous policies of nation. Integrated 3D geospatial information infrastructure will be applied to public

Until now, 3D geospatial information is produced using existing products such as digital maps, and difficulties in representing the real world because of the limitations of portrayal and acquisition problems in digital map operation. So outputs using limited data set have another limit, also. But, 3D geospatial information using state-of-the-art photogrammetric technique can overcome the limitation and realize 3D virtual space which similar to the real national space, from now on. Also, 3D geospatial information construction using aerial photo can diminish or replace the procedures of spatial information construction projects such as orthophoto generation using high resolution digital camera, DEM generation using aerial laser mapping, etc. So it can cut the great amount of a national budget. And it is expected that the project can routinely update spatial information such as large scale digital map which has budget limitation, improve the quality of national spatial information. If realistic 3D geospatial information over whole Korea is constructed, its usefulness will be maximized by synergy effect of operation optimization.

shows the feasibility study results on cost/benefit analysis of 3D geospatial information construction project discounted to the base year 2008). According to the table, B/C ratio is 6.3 and NPV (Net Present Value) is 2,200,163 million won. So, it is proved that 3D spatial information construction project has sufficient benefit and feasibility. Table 7. Tangible Benefits of 3D Geospatial Information Feasibility Study Results (Unit : Million Won)

Current Value of Cost

Current Value of Benefit

B/C

NPV

IRR

415,499

2,615,662

6.3

2,200,163

-

21

Building 3D Geospatial Information using Airborne Multi-Looking Digital Camera System Hyung Tae Kim, Sang Bong Kim, Jong Sik Go, Yang Dam Eo, Byoung Kil Lee

7. References

[16] M. Gruber , S. Schneider, “DIGITAL SURFACE MODELS FROM ULTRACAM-X IMAGES”, PIA07 Photogrammetric Image Analysis - Munich, Germany, September 2007, pp. 19-21. [17] S. Bleisch, S. Nebiker, “Connected 2D and 3D Visualizations for the Interactive Exploration of Spatial Information”, International Society for Photogrammetry and Remote Sensing, 2008, 2008, pp. 1037-1042. [18] J. Britt, G. LaFontaine, “Google Earth: A Virtual Globe for Elementary Geography”, Social studies and the young learner, Vol. 21, No.4, 2009, pp. 20-23. [19] L. Ersen, Z. Baoming, G. Haitao, “Study on the Height Measurement of Cultural Feature Based on the Single Aerial Photo”, International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol. 37, No. B4 pt1, 2008, pp. 63-66. [20] A. Elaksher, “Fusion of hyperspectral images and lidarbased dems for coastal mapping”, 2008, Optics and lasers in engineering , Vol.46, No.7 ,2008, pp. 493-498. [21] A. Georgopoulos, S. Natsis, “A Simpler Method for Large Scale Digital Orthophoto Production”, International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences ,Vol37 no.B5 pt.1 ,2008, pp. 253-258.

[1] MLTM, 3D Spatial Information Construction for Ubiquitous National Administration, 2009. [2] C.W. Seo, Y.S. Choi, J.M. Kim, Y.H. Kim, Y.G. Kim, “Improvement Plan of Quality Control for 3D Geospatial Database”, The Journal of Geographic Information System Association of Korea, Vol. 17, No. 2, 2009, pp.231-241. [3] MLTM, Whitepaper on Current Status of Spatial Information Project, 2009. [4] J.K. Park, W.S. Cho, M.J. Noh, N.H. Song, M.C. Kim, “Improvement Scheme for 3D Land Geospatial Information Construction”, The Journal of Korean GeoSpatial Information System, Vol. 16, No. 4, 2008, pp. 89-99. [5] NGI, Regulations for 3D Spatial Information Operation, Internal Regulation No. 2009-179, 2009. [6] MLTM, Report of the plan on practical use of digital camera for large scale map, 2007. [7] Geoje City, Geoje-si aerial photographing and ortho image map construction project report, 2008. [8] NGI, Regulations for DEM Operation, Regulation for Operation No. 2002-107, 2002. [9] J.W. Jeong, H.J. Jang, Y.S. Kim, W.S. Cho, “Automatic Building Extraction Using LIDAR and Aerial Image”, The Journal of Korean Geo-Spatial Information System, Vol. 13, No. 3, 2005, pp. 59-67. [10] NGI, Regulations for Image Map Production, Regulation for Operation No. 2002-106, 2002. [11] G.R. Kim, K.H. Jin, S.B. Kim, “Accuracy assessment using ortho image and 4 direction oblique images of Pictometry”, Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference, 2009, pp. 519-525. [12] A.F. Habib, E.M. Kim, and C.J. Kim, “New Methodologies for True Orthophoto Generation”, Photogrammetric Engineering & Remote Sensing, Vol. 73, No. 1, January 2007, pp. 25-36. [13] F. Prandi, C. Achille, R. Brumana, F. Fassi, L. Fregonese, “LIDAR AND PICTOMETRY IMAGES INTEGRATED USE FOR 3D MODEL GENERATION”, The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol. XXXVII, Part B2, Beijing 2008. [14] Y. Wang, S. Schultz, F. Giuffrida, “PICTOMETRY'S PROPRIETARY AIRBORNE DIGITAL IMAGING SYSTEM AND ITS APPLICATION IN 3D CITY MODELLING”, The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol. XXXVII, Part B1, Beijing 2008. [15] X. Wang, S. Totaro, F. Taillandier, A.R. Hanson, and Seth Teller, “RECOVERING FACADE TEXTURE AND MICROSTRUCTURE FROM REAL-WORLD IMAGES”, Proc. ISPRS Commission III Symposium on Photogrammetric Computer Vision, Graz, Austria, September 2002, pp. A381-386.

22