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Digital Photogrammetric Workstation On Windows NT

Chen Xiangning, Shi Youyu
ZhengZhou Institute of Surveying & mapping
E-mail: Chen_xn@371.net

Abstract
In this paper, A Digital Photogrammetric Workstation (DPW) on Windows NT which can be used in city planning is brought forward Much new technologies such as image auto-match, computer vision, graphics and image processing are adopted. This system can be applied in large scale digital mapping black and white/color Ortho-image making, city 3D model rebuilding and data of 3D city GIS acquiring / update. It is very effective tool for processing city spatial data.

A Digital Photogrammetric Workstation comprises the computer system stereoscopic display device, 3D measurement device, I/O device and correspond software (Shown in Figure 1 and Figure 2). In the following we’’ll explain the make –up and design of this system through hardware system and software system in detail.

1. The make-up and design of hardware systems
Hardware system consists of the computer system high refresh rate and large screen monitor (dual monitor) Stereoscopic display device, 3D measurement device, I/O device. Their installations are as follows:

(1)The installations of computer system are as follows:
  • Pentium II CPU 300Hz
  • 128MB RAM, 8GMB HD
  • 17” High refresh rate monitor (dual monitor)

    (2)Stereoscopic display device
  • LCD glasses
  • Control emitter

    (3)3D measurement device
  • Hand-wheel Foot-wheel
  • Encode
  • Control switch
  • 3D mouse
  • Date interface card

    (4)I/O device
  • High solution scanner
  • Tape recorder
  • High resolution plotter

    All of the devices and apparatus above are of standard making with the exception of 3D measurement devices and control emitter which are produced by our own research institute.


    Figure1 : DPW photo


    Figure 2 DPW Logical Frame

    2.Make-up and design of software system in the Digital Photogrammetric WorkStation
    The whole system consists of nine model. There are original information control, digital image orientation, DEM extraction, object collection, graphic edit, topographic import, digital aerial triangulation, ortho-image making and 3D model rebuild. The whole system is developed by VC++5.0 in Windows NT 4.0 environment. The make-up of the software system is shown in Figure 3.
  • The function of original information control is to input and manage original information which include aerial photography information, survey area information and survey topographic information.
  • The function of digital image orientation : There are two kinds of system orientations. One is carried on directly by the pixel measurement value of digital aerial triangulation input. The other is carried on by the system itself dependently, which include inter-orientation relative-orientation and absolute-orientation. The above orientation is done by automatic and semi-automatic image match.


    Figure 3 DPW Software Model



  • DEM extraction: It regards stereo-mate as unit, aimed ground point with different elevation according to mark of different interval automatically, extracts DEM, and then piece different models together to form the DEM system of whole area.
  • The function of object collection: Object collection is the foundation for digital measurement. All the object symbols are designed by the mind of Windows NT 4.0. Therefore all the symbols can be represented automatically on the screen as long as position line is given.
  • Graphic edit: Graphic edit is to aim at obtained graphic data, make the digital graphic map to meet the standards of publication. It is one of the important things in the publication of digital functions include object copy, object move, object rotate, object delete, object break, object connect and object clip.
  • Topographic import Topographic import has three kinds of forms to import topographic paper material topographic import, standard graphic change file (DXF), DGN(used MicroStation), ASCII.
  • Digital aerial triangulation: It is not realistic to realize automation for all kinds of region. Therefore this system offers three kinds of working form by hand, semi-automation and automation.
  • Ortho-image fabricate: This model use remote digital image, DEM, photo information, digital graphic map and field investigate information to produce digital ortho-iamge digital orhto-image map digital ortho-image graphic amp after processing. These new kinds of Topographic are imported in grid form and used by user. This software can also use digital image and investigate information to extract object information of graphic map and import in vector form for re-mapping editing or public.
  • 3D model rebuild : This model can use remote ortho-image, DEM and photo control information to produce digital 3D graphic perspective view, and change view point, and have basic space analysis function. By means of this, you can produce static perspective view and dynamic perspective view to serve city programming work.

    3.The conclusion
    The system have already been put to use in business and it can accomplish the making of different-scaled digital topographic, ortho-image and 3D perspective view. It will be widely used in survey and mapping, forestry, agriculture, geology, medicine science, city programming work, and education etc.

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