A Defence roadblock

Print edition : August 26, 2005

Cable being laid for a private telecommunication network in Chennai. GIS applications for development projects will get a boost with the availability of digital maps of the Survey of India. - N.SRIDHARAN

Implementation of the Government of India's map dissemination policy easing restrictions on free public access to topographic data has been delayed apparently because detailed guidelines have been blocked by objections from the Ministry of Defence.

IT is more than two months since the announcement of the new map policy, which allows complete public access to geographic data contained in the topographic maps of the Survey of India (SoI) of all regions of the country and at all scales, including for the purpose of their digitisation and dissemination. It took several years for the government to allow this kind of access since the demand for the same began to be made by the Geographic Information System (GIS) industry, one of the main users of the topographic information for developmental projects involving spatial data. But the detailed guidelines required to make the policy operational have not yet been issued, much to the disappointment of the GIS industry.

Apparently, the Ministry of Defence (MoD) has raised some issues with regard to data pertaining to border areas and the coastal line being made available openly. Restrictions on free access to topographic data (Frontline, October 27, 2000) were in place essentially because of the security concerns of the MoD, the prime user of the data as well as the regulating authority for the map dissemination policy until now. This is indeed surprising because the new map policy, which was evolved in consultation with the MoD (Frontline, February 3, 2001) and which the Cabinet cleared on May 19, has been designed to take care of these.

According to the new policy there will be two series of maps: Defence Series Maps (DSMs) and Open Series Maps (OSMs), a sanitised version where sensitive data, such as military/civil Vulnerable Areas and Vulnerable Points (V.As/V.Ps) and other related data, are removed. The latter will be with respect to a different reference frame and different projection parameters. The DSMs and OSMs will constitute what will be known as the National Topographic Data Base (NTDB). Both V.S Ramamurthy, Secretary, Department of Science and Technology (DST) under which the Survey of India functions, and M. Gopal Rao, the Surveyor-General of India, hope that matters will be sorted out soon and guidelines issued within a month or so.

The existing government restrictions on categories of topographic data (in terms of scales and geographical areas) of the Survey of India maps are governed by an April 15, 1968, notification of the MoD. In effect, this restricts public access to topographic maps of only about 40 per cent of the country's area up to scales of 1:25,000. In the remaining three-fifths of the country, the public has access only to maps of scales less than 1:1 million except in the coastal belt south of 20<108,SYM,176> where the 1:1 million scale is also unrestricted. To access and use the restricted categories of `topomaps', a cumbersome bureaucratic procedure is involved, which includes clearance from the MoD, and an annual certification of continued possession of the accessed data and their use in the ongoing project.

Dissemination of digital data based on the Survey of India topomaps is, however, even more restricted. It is governed by the MoD's Office Memorandum of July 13, 1998. This order was aimed ostensibly at facilitating access to digital topographic data through designated government agencies instead of the hitherto centralised control vested with the Survey of India. In effect, this prevented digitisation of even unrestricted maps by any other individual or agency.

But the new map policy too has been in the works almost since then. As a result, this order has not been implemented, and none of the agencies has so far entered into any MoU with any organisation till date. Also the Kasturirangan Committee, constituted to draw up the guidelines for this arrangement, did not come out with its recommendations soon enough after the order. Effectively, therefore, the situation with regard to access to digital geographic data has remained the same as it was before July 1998. That is, the Survey of India was the only agency authorised to undertake digitisation of its toposheets or its ground survey data. A result of this restriction was the unfortunate incident of an official of the Gujarat Forest and Environment Department being held in 2000 for passing on some restricted maps of regions of Gujarat to a private agency for digitisation.

All this is expected to change following the new policy, and the availability of high quality spatial data should aid GIS applications in infrastructure development. But only if the fresh issues raised by the MoD, which relate to the demarcated area of 50 km inside the coastal line or border, are resolved satisfactorily. In fact, many ongoing developmental projects are within this area and would need digitised topographic data through GIS or otherwise.

The frequently made arguments that high-resolution maps of the Indian region are available on the Internet and from other sources based on satellite imagery are not valid. For one, if they are available freely from other sources, then why all the hullabaloo about restrictions put by the Indian government? The problem is of accuracy and cost. Maps available off the net are based on `raster scan' images and are not `vectorised', which is necessary for GIS application.

Two, any satellite imagery, whatever be its resolution, has to be fixed to a base map based on ground truth measurements for proper orientation. But the accuracy of image products and maps based on remote-sensed data depends on the accuracy of their `geo-coding'. This geo-coding is based on `ground control points (GCPs)' read off base maps of the Survey of India that are used to orient and fix the satellite imagery. Accurate ground control data are held confidential by the Survey of India.

The base maps and GCP data used by the NRSA's for its thematic maps are the Survey of India's 1:50,000 maps. With these, the location accuracy that the NRSA thematic maps achieve is only about 50 metres. The accuracy of maps from foreign sources will be even less because they do not have access to accurate GCP data and usually they are geo-referenced with respect to different `geodetic datum' whose coordination will be relatively shifted with respect to the Survey of India's coordinates. For instance, all GPS measurements, instead of geodetic measurements on a datum like the Everest Spheroid, will be on WGS-84, whose points would have a relative shift with respect to the Everest.

According to the new policy, the DSMs, the defence series of maps, will be on the Everest datum as well as the WGS-84 datum with `polyconical/Universal Transverse Mercator (UTM) projection on various scales and with full accuracy with regard to heights, contours and other features. These will cater to the national security and military requirements. This series, both in analogue and digital format, will be classified and their access will be governed by MoD guidelines.

The OSMs, on the other hand, will be brought out and regulated exclusively by the Survey of India. These will have a different categorisation and will be based on WGS-84 and UTM projection. Each of these OSMs, both in hard copy and digital form, will become "unrestricted" after obtaining a one-line clearance from the MoD.

The usual procedure to go from one reference frame to another is to make use of certain transformation parameters and obtain transformed GCPs and coordination therefrom. Until about a few years ago, apparently accurate transformation parameters for the Indian datum were not available with the Survey of India. According to experts, these were perhaps based on (Doppler) measurements in the neighbourhood region. However, since the decision to bring out separate civilian and military series of maps was taken in 2001, accurate measurements of the transformation parameters have been made and appropriate seamless integration of the various regions has been carried out for going from Everest to WGS-84. The time taken to actually announce the policy is perhaps for this reason.

The Survey of India will be the certifying authority for the use of OSMs, such as procedure for access, further dissemination, value addition and "publication" in hard or soft form (on the Web or as part of a GIS), though the issuance of detailed guidelines seems to have hit an MoD roadblock. A requirement, the implementation of which can get into cumbersome bureaucracy again, is an agreement with the Survey of India for further dissemination by the user agency (with or without value addition) and maintenance of a Map Transaction Registry for every transaction effected.

Although not explicitly clarified in the policy document, the statement that "(the earlier MoD) instructions will continue to hold good but for the modifications cited herein" should logically imply that the July 1998 order (requiring memoranda of understanding with nine agencies) continues to be valid if any agency wishes to access data on the Everest Spheroid, say for reasons of consistency and continuity with earlier use of data by it.

An interesting aspect of the DSMs is that the MoD too will have a series of maps based on WGS-84. According to Gopal Rao, owing to the easy availability of GPS-based measurements, the MoD too expressed interest in maps on the WGS-84 datum. With the removal of "scrambling" by the United States Department of Defence as of May 1, 2001, easy precise positional survey on WGS-84 (based on differential GPS) has become possible and could be used even for defence applications where absolute accuracy may not be needed. Besides, it also helps to monitor the WGS-84-based series of toposheets (with or without value addition) in circulation.

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