Construction of Urban 3-D Model of Hanoi, Vietnam Using FOSS Tools

In this study, we investigate an urban transformation of Hanoi City, Vietnam from topographic changes in the 19-20 centuries. To analyze the relief of terrain and micro-topography for such an urban transfiguration, we need to generate the DEM (Digital Elevation Model) using the elevation survey data. DEM is a digital representation of ground surface topography and the most important element of topographic analysis for urban transfiguration. And, the three dimensional (3-D) mode of buildings which we generated from house map in Hanoi City can be also expressed apparently. It must be useful for an urban transformation because it is difficult to estimate how so many lakes and ponds disappeared by using two dimensional (2-D) spatial analysis only. We generated the DEM (8km x 8km) of Hanoi City from approximately 24,000 points data collected in 2005. This survey data was provided by Hanoi University of Mining and Geology (HUMG). Based on the surface estimation method using Cubic B-Spline Function, we generated this DEM at 2 meters resolution (Nonogaki et al., 2008). The very subtle elevation gaps which can not be distinguished on the satellite image are significantly recognizable on it. The example of the visualization of 3-D DEM is shown in Figure 1 using the NVIZ of visualization tool in GRASS GIS software. It is overlaid the Hanoi road map on the generated DEM. We generated the vector map of each block of houses in the Pho Co district in Hanoi City by using the house maps in 2005 which are provided by HUMG. It is consisted of 12,000 polygon data. These are converted the 3-D data (features) using the GIS software. This 3-D model is not only visualized the landscape in the Pho Co district accurately, but also reflected the elevation in this area. Thus, the 3-D features are built on DEM which is shown in Chapter 3. Therefore, we can create an overview of how the current urbanization is advancing in the area where the lakes and ponds existed in the past. Example of the visualization of 3-D DEM.