Prof. Prabhakar Misra
Director, GIS Institute
B to B is, a standard vocabulary in IT to denote transactions from ‘Business to Business. The same word is now being utilised to convey ‘Back to Basics’ to those who wandered far away to chase exciting but imaginary goals which came to light after the fall of dot.coms. The profession of Surveying, also on the similar analogy, needs rethinking on its policies, priorities and performance. The users specially from GIS sector have exposed the weak spots of the surveying practices in India. Some policies which directly affect the cost and quality of map products have been discussed with examples in this paper.
Historical Scenario of Geometry versus/and Contents of the Mapping policy
There used to be a conference called Survey Priorty Conference. The major function of this body was to allocate the survey resources of Survey of India (counted as units of Party-year) for various projects in India. The irony was that surveying resources fell much short of the requirements to the extent that one more Survey of India (SoI) is required for one year. The obvious solution which came to mind was arithmetic-expansion of the Survey of India. It was, however, rightly preferred to have the technological (productivity) expansion of the Survey of India, employing newer technologies like aerial photography and photogrammetry.
While this was happening, the 1:50,000 coverage of the whole of India was completed by the Survey of India in late seventies. SOI was then fully poised to launch the mapping on 1:25,000 scale. This scale could have also satisfied the departments like Forest Departments in the States even though the foresters were used to a much larger scale of 4 inches to 1 mile. (1:16,000 or so). The scale of 1:25,000 is quite optimum from the point of geometry and contents.
This programme had a partial set back because a new technology of satellite remote sensing appeared on the horizon in India in mid seventies, raising hopes of miracles. Users and organisations/departments missed the point that these technologies are more oriented towards ‘contents’ of the map rather than the ‘geometry’.
This tussle between Geometry vs. Contents still goes on to day. The user has to design the mix between geometry and the contents. Consideration of geometry is rather important for large scale maps e.g. Urban base maps (urban GIS). This is explained further. Since a major cost would have incurred on Urban Base Maps, there is a large vacuum in the policy and investment on these base maps.
Urban Base Maps are not yet Available
Yet another factor which enhances the woes of an Urban-GIS project is that, except for a few towns, professionally prepared Base-Maps are not available. Out of a total of about 600 important towns in India, the base maps of ‘some sort’ are available only for about 200 Urban Development Authorities. Many Development Authorities are still getting the maps prepared out of plane tabling and mosaicing of revenue maps. In short geometrically reliable base-map layer on scales of 1:5,000/1:10,000 is hardly available to make a start of an Urban-GIS Project. As a matter of reality the shortcomings of accuracy (geometry) are getting camouflaged by the computer oriented processes.
If we consider utility maps on scales as large as 1:2,000, there are hardly any success stories except for Delhi Metro Area where 1:2,000 scale digital maps are being produced by the National Informatics Centre (NIC).
The meagre photogrammetric capacity of NIC can be enhanced several times by adopting the policy of Public Private Participation (PPP). This model has recently been adopted by the National Remote Sensing Agency to augment its photogrammetric capacity by pooling resource of private photogrammetric companies. The private companies have set up their instruments in the premises of NRSA.
Public – Private Participation: Need of the Hour
The solution(s) to the problems of scarcity of digitised maps and control data may, perhaps, lie in the change of policies. The present day surveying organisations need outside support in augmenting their potential in a synergistic manner. Private organisations in surveying sector – although their number is not large – can be harnessed to work alongside the Government sector. Can we divide the work between these two sectors? The answer is an emphatic YES. The infrastructure comprising control points and geometry can be entrusted to the Government in PPP mode and leave the rest of the job to the private sector.
Basic Infrastructure (Geometry) with Government Departments
Let Central/State Government organisations concentrate on the primary sector of the surveying. The primary activities will include, inter alia, the following functions:
- Defence/security oriented ground control through traditional techniques and GPS technology.
- First order leveling, triangulation and establishment of primary GPS control for Ground Control Points (GCPs) as required by the Department of Space, Universities and engineering projects.
- Control and surveying along the border and coastal areas. This is already being done by Naval Hydrographic Office and GSGS of the Army.
- The density of the horizontal control as well as the elevation control (through Bench Marks) should be enhanced to a level so that a subsequent connection of control to a specific project area does not exceed 10 to 20 kms.
- All National and State highways running to a length of 1,65,000 km should have GPS/levelling control as mentioned above.
- There should be arrangements for central data clearance of these data to minimise the running about and time required for data gathering.
Once the basic infrastructure is in place, PPP concept will provide the contents and updating.
Modern Technologies for ‘Contents’ of the Map
Aerial photography, Photogrammetry and Satellite Image grammetry
The aerial photography and the subsequent photogrammetry has been in vogue in India since late fifties. The fact is that large scale maps on 1:2,000 scale are best produced through photogrammetry which fulfills the requirements of accuracy. This concept of accuracy is also applicable to the elevations depicted through close contours. An accuracy of 20 cms in elevations is being delivered in a routine manner from 1:8,000 scale of photography. The plan accuracy of 10 cms on 1:2,000 scale is also being achieved. The major advantage to the map – user comes in the form of reduced cost of mapping and marked savings in time.
The main snag in using the technology of photogrammetry in India has remained in the form of the security environment prevalent in India. Consequently, the technology has not prospered in India. This has resulted in deprivation of some products like orthophotomaps in Indian scenario.
There is, however, a chance of big revival of photogrammetry in its new avatar of image-grammetry. This impetus is going to come from the high resolution (1 metre) stereo – satellite imagery. The biggest gain will be in the form of digital – orthophoto-mapping at large scales.
Satellite Remote Sensing
The technology based on satellite imagery which came to India in mid-seventies proved its worth in providing contents to many thematic maps, namely forestry, geology, soils and ground water etc. Its basic strong point of providing ‘repeated contents to the thematic maps has been of maximum use to the mapping of natural resources and small scale GIS, including modeling.
The satellite imagery today is capable of providing ‘contents/updation to any scale from 1:4,000 and smaller. Providing ‘contents is no more a worry to the map-maker.
Policy of Revision and Updating
The most difficult job for a surveyor is to provide the field control network of the desired accuracy both in plan and elevation. The technology provided by the Total Station, GPS and other techniques makes the control job a little easier. These technologies are, therefore, extensively utilised for control. The accuracy of the mapping will depend on this control.
The ‘contents’ of the map/data set are derived from the satellite imagery of the proper resolution, aerial photography and subsequent photogrammetry. The scale of the map determines the contents and the geometry (or vice versa).
Once the consideration of ‘geometry’ and ‘contents’ have been properly weighed and designed, the final map is prepared in digital or hard copy form.
If the map is produced according to the consideration as mentioned above, the process of updating/revising of the map becomes easier as each topographical feature e.g road junction, corner of the building acts as a pseudo – control point for updating/revision of the area in the vicinity of the pseudo-control point. Further the availability of high-resolution satellite imagery of Indian CARTOSAT is a definite possibility to most of the users.
In such a scenario where geometry and contents are already available, the updating of the maps can be professionally entrusted to the private sector. This argument can be extended to the revision of the Survey of India’s topographical maps on 1:50,000, 1:25,000 and other scales. A policy can be formulated that updation/revision should be reserved for private sector only.
Private sector may also like to bring out many value-added products based on the primary maps produced by the Government agencies. One example could be the Slope Map produced from contours produced by Survey of India.
Dessimination of Spatial Information
First requirement before start of any mapping activity is to know ‘what is available and where’. For this purpose we may have to contact a large number of Departments/offices where the physical (spatial) information is lodged. One easy course of action is to reach the web site of the concerned office, if available.
This suggestion has also been made to the National Geospatial Database Intiative (NGDI) which is a forum where all data generating organisations are able to interact with each other. Meanwhile, the data can be disseminated through their respective newsletters.
Summary and Conclusions
Three major ingredients of the mapping process, namely, Geometry (control), Contents and Updation have been emphasised. It is also suggested that Government should focus on providing the geometry and related country wide control, etc. The ‘contents’ of the map which are easily obtained through satellite imagery and updation of maps should be left to the private sector. Strong suggestion has been made that Government Department should outsource its tasks (to the extent possible) to outside private agencies.
All the above mentioned suggestions/thoughts would make a big difference to the cost (maponomics) of the map/data and its timely availability to the user. The right changes in policies not only save the costs but generate additional opportunities and challenges for the profession. The professional and organisational leaders should continue to review the existing policies affecting maponomics and allied issues.