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

and not in well defined network mode. For adjustment, a network was required to be
formed. When the Continuously Operating Reference Stations are included in the
network, hundreds of baselines are formed by the common observations among
CORS and Phase-I GCPs. By carefully selecting few hundred baselines out of these
baselines, a network of more than 300 interconnected triangles was formed. The
network is in such a way that all the GCPs and most of the Continuously Operating
Reference Stations are connected.
In the first step, all the baselines are being computed using Bernese GPS
Data Processing Software. The second step will be connecting the CORS to the IGS
stations. This is necessary to connect the Indian datum with the ITRF as per the IAG
recommendations. The CORS network will be adjusted and coordinates will be
computed on the epoch 1st January 2007, taking the IGS stations as fiducial
stations. This will be done using scientific GPS data processing software Bernese
5.0. The CORS will then be used as known stations and the GCP Phase-I network
will be adjusted. The slope distances will be computed using Bernese 5.0 and will be
reduced to ellipsoidal arc distances using a computer program. These ellipsoidal arc
distances will be taken as observables and the adjustment will be carried out using
ADJUST program developed by National Geodetic Survey (NGS), USA and freely
available on the internet. This realization will be based on ITRF2005 which has the
epoch 1st January 2000. Using the velocity model, the epoch of this realization will
be kept 1st January 2007.
Phase II, additional 2200 GCPs of First Order Ground Control Points will be
established at an average of 30 km spacing all over the country. GPS observations
are carried out for 6-8 hours at these stations and the base lines are computed using
adjustment software. The station coordinates are adjusted with Zero order control
points as per usual survey principle “whole to part” .the expected accuracy of
horizontal coordinate is in the order of 0``.002 amounting to 6 cms on ground. The
First order control points will be connected by leveling .Work is under progress. It can
be completed in 12 months, if top priority is given to this job and some
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