The Production of Photo Base Map in Taiwan
4. Photo Base Map Production
4.1 Analog Mapping System
From the fiscal year 1976 to 1999, the analog photomap production reached a total of 15,160 sheets. The details are as follows :
Table 1 Production of Analog Maps
| Fiscal Year |
Areas |
Completed
Sheets |
Scale |
1976-1982
(Base map) |
Taiwan, Pescadores |
3,209
564 |
1/5,000
1/10,000 |
1983-1987
(Base map 1st revision ) |
Taiwan
(western urban areas) |
2,000 |
1/5,000 |
1985-1989
(Coastal map) |
Taiwan
(coast region) |
3,256 |
1/1,000 |
1987-1999
(Forest map) |
National forest
(37 working circles) |
3,731 |
1/5,000 |
1989-1995
(Base map 2nd revision ) |
Taiwan
(western urban areas) |
2,400 |
1/5,000 |
| Total |
|
15,160 |
|
4.2 Digital Mapping System
From the fiscal year 1995 to 1999, the digital photomap production was 1,580 sheets. The details are as follows :
Table 2 Production of Digital Maps
| Fiscal Year |
Areas |
Completed
Sheets |
Scale |
1995-1999
(Base map) |
Tai-chuug,Nan-ton,Chang-hua,
Yun-lin,Chia-yi,Kao-hsiung,
Ping-tung |
856 |
1/5,000 |
1997
(Photomap) |
NTU Experiment Forest
Erh-chung spill way |
80
40 |
1/5,000
1/1,000 |
1997-1999
(Forest map) |
National forest
6 working circles |
604 |
1/5,000 |
| Total |
|
1,580 |
|
5. Digital Mapping Procedures
5.1 Flight Plan
- Formulate the aerial photography implementation project (includes : areas to be photographed, flight routes, flight altitude, photo scale, photo end lap and side lap requirements, weather condition etc.)
- Application for aerial photography. (Ministry of Interior)
- Application for special flight .(Ministry of Communication)
5.2 Ground Control Targeting
Prior to aerial photography, the ground targets must be placed on the control points in the areas to be photographed. The white rectangular plastic sheets are laid out around each control point to form a landmark in the shape of a cross or the letter Y or T. This will facilitate the identification of the location of the control points to be shown on the photographs.
5.3 Aerial Photography
Aerial photography is implemented by the Agricultural and Forestry Aerial Survey Institute in cooperation with the Aeronautic Team of the Ministry of Communication. Two aircrafts, Super King Air Beechcraft 200 and Beechcraft 350 with GPS navigation are used to take the aerial photographs for mapping purposes. The camera used are Zeiss RMK TOP series, focus 15/23 and 30/23. The flying crew consists of a pilot, a copilot, a cameraman, a supervisor and a mechanician.
5.4 Photo Processing
Black/White Aerial Film Processor and Color Aerial Film Processor are used for photo processing.
5.5 Ground Control Survey
There are two ground control survey systems. One is horizontal and the other is vertical. Trimble SSI and Trimble 4700 are used for the horizontal control survey and the Wild 2002A digital level is used for the elevation surveys based on the benchmarks on the known elevation point.
5.6 Photo Scanning
There are two instruments employed for digital photo scanning . One is Photogrammetric Workstation (PS-1) used for individual films, resolution ranges from 7.5, 15, 22.5, 30, 60, 120, 240 micron. The other is Photogrammetric Workstation (PS-TD) used for both roll films and individual films, resolution ranges from 7, 14, 21, 28, 56, 112, 224 micron.
5.7 DTM Recording
Ground DTM = 40m ×40m or 20m ×20m by manual
Cover DTM = 9m ×9m by automatic Match-T Program
5.8 Measurements and Triangulation
Aerial triangulation is a triangulation survey based on aerial photographs to minimize ground survey work. Each aerial triangulation block consists of about 200 maps. The control points along the boundaries of the triangulation block are GPS surveyed, but the control points inside the block are measured from photographs. With the aid of a computer---Zeiss C-100 Planicomp Analytical Steroplotter, the PAT-M-43 program is used for aerial triangulation computation. All the measurements on aerial photographs are adjusted and tied to the ground coordinates.
5.9 Contour Line Plotting
Zeiss P33/PC Digital Analytical Stereoplotter is used for the contour line; break line; hydrograph and spot height plotting.
