High Resolution 1:10,000 scale Mapping Strategy of Multi ... - NDMA

APPENDIX- XXI
POSSIBLE PPP MODEL WITH SOI UNDER NEW MAP
POLICY
It may be opportune at this moment, for better appreciation of the constraints of the
SOI, to briefly dwell upon the various processes and procedures followed for the
generation of a base map by the SOI. The primary source for generation of map is
“Aerial Photographs” (AP’s). Securing AP’s itself is a tedious and time consuming
process. First a dedicated aircraft with special fitments has to be available. Aircrafts
are available only with the IAF, which insists for a rigorous security regime entailing a
slew of clearances. On the day of aerial surveys, the sky has to be cloud free. In fact
there is an extremely narrow window of 30 days or so, when we have cloud free days
within the year. It is reasonable and realistic to presume that aerial survey of the
entire country de novo can take a minimum of 3 years. In order to get a 3
dimensional view of each “scene” on the ground, which is a must for vertical
elevations of the ground (contours), we should have image of the same area from
two vantage points thereby enabling “stereoscopic vision”. The AP’s so obtained
have to be corrected for a series of noise errors for relief distortions. After completion
of all these processes, we get what are known as “orthophoto images”. It is from
orthophotos that we derive maps after extensive groundtruthing aided with the use of
Ground Control Points (GCP’s). A summarized version of this elaborate and
sequential process is given below.
(i) Procurement of AP’s
(ii) Providing Ground Control Points (GCP’s)
(iii) Geo-rectification of AP’s
(iv) Generation of Digital Elevation Model (DEM) and Orthophotos
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