A 3D model of the Inner City of Beijing Chiu-Shui Chan, - PowerPoint PPT Presentation

A 3D model of the Inner City of Beijing Chiu-Shui Chan, Architecture / VRAC, ISU Anrong Dang, Architecture, Tsinghua University Ziyu Tong, Architecture, Southeast University

Mission statements • Explore methods for creating a digital city. • The digital city should be able to: -- visualize urban forms. -- evaluate urban design.

Outline 1. Introduction of the city 2. Objectives 3. Methods 4. Benefits and challenges 5. Future studies

The city of Beijing • Beijing has more than 3,000 years of history. • The capital of: � Yuan dynasty (1271-1368), � Ming dynasty (1368-1644), � Qing dynasty (1644-1911). • Many significant cultural sites, particularly in the Inner City area.

The Inner City -- The Inner City has an area of 64 square kilometers. -- Located in the center of the metropolitan area. -- Regarded as the cultural heart of the region. -- Two UNESCO World Heritage sites: 1. The Temple of Heaven, and 2. The Forbidden City. -- It also contains groups of famous courtyard houses.

Forbidden City Temple of Heaven Xidan Business District – panoramic view

Objectives / purposes -- Beijing is facing rapid urbanization and quickly modernizing. -- Planners need to maintain the sustainability of the old city and to preserve the cultural heritage. -- A tool is required for studying the urban space and form. -- Traditionally, a 3D physical model is utilized. -- But, A virtual reality (VR) digital city serves the purpose even better --- it gives a better visualization for spatial analysis. -- Particularly, a full-scale immersive environment would be even better.

Data acquisition for modeling -- Collect city drawing data, however, many old drawings are not to scale, -- Most new drawings are not available. -- No powerful 3D scanner or laser sensor available. -- New method of applying aerial photo through Remote Sensing (RS) and GIS to get data. -- Also apply the Bldg Height Regulation map.

Method of data acquisition Building height control map, 1991 Satellite photo, 2001

Modeling sequence (1) Construct a volumetric regulated city model, (2) Collect up-to-date 2D and 3D information from satellite images to create an existing city model, (3) Develop a coding system for establishing a GIS database, Create detailed 3D MAX building models � VRML, (4) (5) Combine the regulated and existing models together, (6) Combine the existing and detailed models together, (7) Put the combined models in a CAVE facility for immersive display.

Bldg Height Control model

Existing city model Step 1: Select a satellite image. Based on the quality of resolution, swath width, digitizing bits, and the off- nadir angle of the RS images, an QuickBird satellite image (October 18, 2001) was selected.

Existing model -- RS Image Processing The QuickBird satellite produces a high-resolution 61-CM panchromatic image (black and white) and a 2.44-M multi- spectral image (blue, green, red, near-infrared). Economically, the cost per square meter is lower than other satellite images.

RS Image Processing The 61-CM panchromatic and 2.44-M images are merged using ERDAS image processing fusion techniques into a multi-spectral, high-resolution image.

Existing model -- Database Step 2: Extract spatial information from the resulting image. 2D shapes of each building or city blocks was developed (in GIS ArcView) based on the image color, shape, texture, and pattern to get information on area, perimeter, and building ID.

GIS Spatial Data The 3D information of each building height was calculated by measuring the shadows’ length shown in the image, which was determined by the elevation and azimuth of the sun (the length and direction of shadows) and the satellite (the length and direction of the oblique projection).

GIS Spatial Data -- The height of 4 buildings in one city block was tested. -- Errors between the calculated and actual height are less than 47 CM --- the method is acceptable for a volumetric model.

Current existing city model Step 3: develop a 3D model. -- By applying the coding system and calculating the building height, a 3D model was created by the 3D analysis function in GIS.

Current existing city model The 3D GIS model and the GIS spatial database can be operated interactively. Clicking on any building in the GIS model will list the relative attributes in the attribute table, providing information to evaluate design.

Detailed model Step 4: develop detailed digital models of the Temple of Heaven, Xidan Business District, a hutong in 3D MAX.

Combine existing & detailed models Xidan Business District -- Visualize the urban form

-- visualize the urban form Temple of Heaven

VR models -- VRML Step 5: A VR city was created by combining the detailed and the volumetric models together and viewing them in a VRML browser. -- Texture rendering was modified, -- The Level of Detail was added.

VR model in CAVE Step 6: convert the VRML model to a CAVE model. -- The model was handled by the VR-Juggler, graphically displayed by OpenSG, viewed at C6 -- an enclosed 6-sided CAVE facility. -- Provide sense of presence in the virtual environment.

C6 – Immersive VR facilities

C6 Display–wire frame representation

Applications of the city models • Combine the volumetric regulated model and existing forms together to check urban planning issues. • To study historical development.

Regulated urban form -- A flat region is suggested. -- Maximum regulation is 45 meters.

Height regulations Planning Height Sum_Area Percentage (M 2 ) Land-use (M) Count (%) Green space 0 12 71406.01 4.02 Preserved 4 2 31734.65 1.78 09 M 9 5 92149.48 5.18 12 M 12 15 191196.11 10.75 18 M 18 30 629277.19 35.39 24 M 24 9 77472.97 4.36 30 M 30 22 405661.22 22.81 45 M 45 15 279438.68 15.71 Total / Average 110 1778336.3 100

Existing urban form -- It shows the character of the district. -- The location of high-rise buildings are scattered.

Combine Regulated & Existing models

Buildings taller than planned -- Visualize buildings that are taller than the assigned height. -- Some buildings exceed the maximum regulation of 45 meters.

Buildings outside the redlines -- Some buildings are located outside the planned streets.

Courtyard houses -- Courtyard buildings are 4 meters height. -- Will be replaced by high-rise apartments / commercial buildings. -- The characteristic of the district will be changed.

Applications of the city models • To study historical development. -- Original form in Yuan dynasty.

Benefit and Challenges -- A new method for acquiring 2D & 3D information. -- It is good for volumetric forms. -- Couldn’t get heights for shadows within a shadow. -- Coding system is good for database management. -- It applies to the local region only.

Benefit and Challenges -- GIS spatial database can be used to create 3D model. -- Only a primitive form. -- The data of spatial structure and building form can be used dynamically. -- Data entry is time consuming. -- The VR model is significant for viewing the whole city. -- Memory size and run time speed.

Future Studies 1. 3D model can be used to aid urban planning, analyze urban form, compare skyline, quantify architectural density, calculate traffic flow, judge building design, and evaluate urban planning results. 2. It is expected that this project could explore more on methodologies of visualizing urban codes graphically.

Future Studies 1. A city is a very complicated organic form. 2. It would dynamically generate urban information every day, hour, minute and seconds. 3. If these information data could be collected efficiently as a data bank, it would be a very rich set of resources for urban decision making. 4. If a digital city could simulate the physical urban dynamically, then its power of application is tremendous.

Acknowledgments -- Supported by the National Science Foundation #0089884. -- Team includes faculty members, graduate students and undergraduate students from Iowa State University, visiting scholars from four universities in China.