1.0 Background
Since 1902, the Survey Department of Sri Lanka has been responsible for producing, large and small scale geo-information to its users. The small scale topographic information was produced to the users in the standard map forms in the users in the standard map forms in the scales of 1:63,360 and 1:50,000. New map series on 1:50,000 and 1:10,000 scale commenced in the year 1981 and 98% of 1:50,000 and 18% of 1:10,000 completed upto data. Although the data capturing is carried out using computer integrated photogrammetric equipments, the cartographic process and the printing of final maps are time consuming. For this reason it is not possible to provide the user with timely geo-information.
New technology development of hardware and multimedia software have given us the potentiality to add to the new functionality for he current system. This paper deals with the proposal for the establishment of a topographic database structure for the department in order to expedite the supply of geo-information to its diversified users.
More specifically the following topics will be discussed.
- the role and structure of the geo-information production process at present and proposals for the future.
- Design of a topographic database
- The functionality requirements (hardware/software/manware)
2.0 The present Structure of the Gen-information Production.
Survey Department is responsible for producing scales of 1:50,000 and 1:10,000 topographic information and thematic information such as Landuse. Presently, the department is supplied the geo-information in the form of conventional paper maps. These conventional map production and currently available information is summarized in table 1.9
2.1 Topographic Map Production
Main data capturing for topographic map production is based on aerial photographs using computer integrated photogrammetric equipments. The plotted map sheets are then to be sent for field verification. Checked and completed information is fed to the draugting section for cartographic work for map printing. The several units contribute in producing these maps. Figure 1.0 shows the present production line and staff involvement.
Considering the present situation of the 1:10,000 topographic mapping process out of 566 of the plotted manuscript 307 is in the standard map form. Data source of some of the plotted manuscript were 1984 aerial photographs and those have yet to be completed, it is difficult to provide timely geo-information to the users.
Table 1.0: Currently available information in the Survey Department
| Maps | No. of maps to cover the island | Commenced in | Completed | Completed up to data |
| 1:50,000 Topographic Maps | 92 | 1981 | 1996 | 98% |
| 1:10,000 Topographic Maps | 1834 | 1981 | | 18% |
| 1:100,000 Landue Maps | 24 | 1981 | 1990 | 100% |
Figure 1.0. The present statistics shows the flow of production is time consuming and depend on the work of the different work groups.
2.2Landuse Map Production
Landuse patterns are extracted from aerial photographs by visual interpretation. The extracted features were compiled to the base of geometrically corrected LANDSAT MSS images. Compiled information were then checked and field verified. Afterthat, necessary cartographic work done in order to produce printed paper maps.
2.3 Limitaitions of the Conventional Maps in the Department
The conventional maps is the available media for storage and presentation of terrain features. Various symbols, line types, shapes, color and the map legend provide explanations and classification of map elements. Since the map is scale dependent, the acquired terrain features either with other related features, in order to present in a map form.
On the other hand, retrieval information from map and their combination with other surveys about specific properties of the earth's surface are neither easynor cheap nor cheap task. In addition to the cost and time required in the compilation and publication of printed maps, the systematic nature of conventional mapping programs can leads to delays in the development programs and in responding to urgent needs for topographic information.
When analyzing he present situation and the limitations of the conventional mapping procedures, it reflects that the line of production has to be reviewed and it is justifiable to introduce new concept for geo-information production within the department.
