The datum debate continues

Feb 2007 | Comments Off on The datum debate continues

Dr Kumar says solutions are available, Do you agree?

Indian geodesists have the know-how and expertise to carry out these tasks. Of course, all help from expert agencies like National Geodetic Survey, USA; DMA, USA, and expert persons like Dr Muneendra Kumar is welcome and should be taken. Unfortunately, many of our Government departments like SoI do not make use of the expertise available outside their own Department, like experts in other scientifi c and academic organisations and Institutes, retired Geodesists, etc. Their contribution and advice would be of great help in putting these highly scientifi c tasks on the right track and in expediting them. Probably an eminent and young, dynamic Geodesist as Head of SoI would be able to provide the leadership and guidance required for these important national tasks!

Not advisable to stick to weak datum: LT GEN SURINDAR P MEHTA

Questions have been raised at various quarters whether the Vision invoked
by the President can be fulfilled by using 19th century Datum.

Before I comment on this, let us review briefl y the broad classifi cation
of Mapping /Cartographic effort required for various applications.
• Cartography for Global level planning and execution. This calls for most accurate techniques to depict the shape and size of the earth. Requires most accurate absolute positioning of points on globe to ascertain correct distance, directions, areas, volumes, essential for various global activities such as Global Warfare, Continental Drift, etc. Also involves very precise
measurements of International boundaries. There is the requirement of most precise control network based on well defi ned Datum.

• Cartography for Macro level planning and execution. Requires depiction of all major topographical details (both physical and manmade) relatively correct to enable macro level study and planning of land related activities. Topographical maps on scale 1:25000 to 1:250000 have been used. Relative accuracy is important and distance, area and volume can be computed within limited accuracy, generally acceptable for macro level planning. Any suitable cartographic projection with any reasonable datum can serve the purpose.

• Cartography for Micro level planning and execution. This requires all terrain data accurate in size and shape in relative correct position so as to get true distance, area and volumes for micro level planning and execution of land related projects. These are large scale maps of the small area of interest. Some of the Engineering projects ( such as Irrigation) , require study on map scale 1:5000 to 1:10000 and further detailed planning, design and execution on larger scale (1:1000 or even larger). Relative accuracy of positioning of details is the prime requirement and absolute positioning and well defined datum is not mendatory.
Let us now examine major inputs required for various requirements projected by the President.

Providing Urban Amenities in Rural Areas

Requires mapping on large scale (1:10000 or larger 1: 2000) for 7000 PURAS (6 lakhs villages / 2 lakhs panchayats) in 2 years time. Requires huge survey and mapping effort. It is advisable to collect terrain data based on the existing control network , rather than waiting for any new Datum defi nition


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