The high-resolution, textured, and 3D mesh model of the Hong Kong Special Administrative Region Government Planning Department’s 3D planning and design system adopts oblique photogrammetry technology.
We provide the following services：
i. Using oblique photogrammetry technology to capture buildings and features in a designated area of interest (AOI), which is approximately 48 square kilometers;
ii.Post-processing the data and providing the 3D Mesh Models as OpenSceneGraph binary(OSGB)&3DML format;
iii.Performing quality check for the data capture and post processing;
iv.Providing the Digital Surface Model (DSM),orthophoto,dense point cloud and raw digital aerial photos of the specified AOI.
Format,Resolution and Accuracy
| Items | Format | Minimum
Required Resolution (GSD) |
Absolute Accuracy
(90%confidence) |
Relative Accuracy
(90%confidence) |
|||
| Horizontal | Vertical | Horizontal | Vertical | ||||
| 1 | 3D Mesh Models with
level-of-detail (LOD) |
OSGB &
3DML |
0.1m | 0.3m | 0.5m | 0.1m | 0.2m |
| 2 | Digital Surface Model (DSM) | TIFF | 0.1m | 0.3m | 0.5m | 0.1m | 0.2m |
| 3 | Orthophoto | TIFF & ECW | 0.1m | 0.3m | 0.1m | ||
| 4 | Dense Point Cloud with colour
information on each point |
LAS | 4 pts per
square meter |
0.5m | 0.5m | 0.2m | 0.2m |
| 5 | Raw Digital Aerial Photos | TIFF & JPEG | |||||
| 6 | ContextCapture project
file |
CCM | |||||
| 7 | Flight information with photo index | SHP | |||||
| 8 | Ground Control Point &Location Plan | XLS&PDF | |||||
| 9 | Index Plan for 3D Mesh ModelsTiles | SHP |
Technical Requirements
1.All coordinate data and geo-referencing shall refer to Hong Kong 1980 Grid coordinate system.
2.No cloud or cloud shadow should obscure detail on any area being photographed. The photography will not be accepted when smoke,haze or any other conditions would impair the quality of the aerial photographs.Cloud cover of more than 10% will not be permitted.
3.All photogrammetric surveying purposes require sufficient horizontal and vertical control measurements. All horizontal and vertical control measurements should be conducted using procedures and/or accuracy standards consistent with professional surveying and photogrammetry practices.
4.It is necessary to establish a sufficient number of control points to meet accuracy requirements and quality control requirements. The control points should be located on clear and identifiable features or points identified by the contractor. The control points should be:
i.Have a clear view of the sky;
ii.Located in a relatively level terrain,away from steep terrain;
ii.Located in areas where the identified target has a high probability of remaining undisturbed during the work assignment.
5.The accuracy requirements for control points shall not exceed 0.05m for horizontal(X and Y)and not exceed 0.15m for vertical (Z).
6.The 2DSM shall meet absolute horizontal accuracy of +/-0.3m and absolute vertical accuracy of+/-0.5m for a confidence level of 90%. The 3DSM shall meet relative horizontal accuracy of +1-0.1m and relative vertical accuracy of+/-0.2m for a confidence level of 90%.
7.Colour and tonal balancing shall be applied to the orthophoto to give clear image, sufficient contrast,good radiometric quality,natural colour
and continuous tone.The orthophoto shall have well balanced brightness and colour histogram.
8.Provide dense point clouds in a universal LiDAR data exchange format (.las). The Dense Point Cloud shall have colour information on each point and have a density of minimum 4 pts per square meter.
9.The Dense Point Cloud shall meet absolute horizontal accuracy of +/-0.5m and absolute vertical accuracy of+/-0.5m for a confidence level of 90%. The Dense Point Cloud shall meet relative horizontal accuracy of+/-0.2m and relative vertical accuracy of+/-0.2m for a confidence level of 90%.
10.Provide original digital aerial photographs.