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.

 

 

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