Development of indian electronic navigational charts (enc)

Initial accomplishments in indian ENC programme
The Electronic Navigational Charting programme of India started with a vision to gain a greater appreciation and understanding of the use of electronic charts when operating in its waters. Beside this the purpose was to develop an information system and demonstrate world that India is capable of producing full coverage of its National Chart series digitally and as per the specifications laid down by IHO/IMO.

With a solid core of experienced cartographers and Hydrographer, equipments and the nations most extensive holding of bathymetric and hydrographic data, a quest for development of Electronic navigational Charts started in 1997. For Indian hydrographic Office creating Electronic Navigational Charts for its waters was a very prestigious project. Initial hurdles include source for generating ENCs and populating it with data. The obvious choice for source for its creation was initially paper chart, although limitations of a paper chart is that if it is used for creation of ENC to enrich it, all the limitations corresponding to the scale would be transferred to ENC, but due to financial and other constraints it was decided to digitized the paper chart information for the purpose of creating ENCs rather than going for original source material. Then came the problem of finance and after careful review the task was contracted to an Indian firm who then utilized CARISTM Suite of Software for implementing S-57 standards of IHO/IMO for obtaining full coverage as per national chart series of India. Stringent QA/QC checks were employed to follow that resultant product i.e. ENCs are fully compliant as per IHO Product specifications and as a result India attained full ENC coverage of its Indian waters in 2002. (Fig 3)

Fig 3. ENC coverage of indian water
The scale of a ENC is determined by the type of navigation for which it is intended, the nature of the area to be covered and the quantity of information to be shown. Various scale terms are used in the S-57 IHO Product Specifications Appendix B, such as Overview, General, Coastal, Approach, Harbour and Berthing which belongs to Chart series of medium-scale, large-scale, and coastal series. The IHO product specifications for ENCs although mentions navigational purpose of ENCs, but it did not specify the scale range that should be applied to each ENC. The reason behind it is that different HOs have their own scale ranges to meet the navigational purpose. The Indian Hydrographic Office followed INT M4 chart specifications for the simple reason that each ENC cell is roughly equivalent to limits as per paper chart.

As per IHO S-57 Product Specifications Appendix B India produced 253 ENC cell with usage band/scale range as given in the Table 1 below along with Fig 4 showing graphical presentation of percentages of Indian ENCs based on usage index:

Table 1

Code	Scale Range	Navigational Purpose	No of Charts in Usage band
1	1:3.5- smaller	Overview	8
2	1:500,000-1:1.5M	General	10
3	1:150,000-1:300,000	Coastal	62
4	1:37,500-1:100,000	Approach	56
5	1:25,000-1:35,000	Harbour	107
6	1:6000-1:20,000	Berthing	10
		TOTAL	253

Fig 4 Indian ENCs ratio based on usage band