  Kodaikanal Observatory is a veritable treasure trove of data, with the data
repository covering almost 100 years of observations. For the years 1909-2007,
we use calibrated Ca II K spectroheliograms from the Kodaikanal Observatory to
detect the plages, fix their heliographic coordinates and also estimate the
plage areas. We adopt the following procedure. After ensuring that, for all the
years, Kodai calcium images have very negligible ellipcity, a circle is fitted
and two central coordinates and radius of calcium images are determined
uniquely. For each pixel of the calcium image, we then fix heliographic
coordinates and extract plages along with their weighted average coordinates.
The heliographic coordinates of these extracted plages are then compared with
the heliographic coordinates of photospheric sunspots from the Greenwich
sunspot database and chromospheric magnetic plages detected from the SOHO/MDI
magnetograms. We find that the heliographic coordinates of calcium plages match
very well with the heliographic coordinates of sunspots and magnetic plages
authenticating our method of detection of plages and computation of positional
coordinates. A code is developed in Python and all the nearly century scale
plages data, with accurately estimated heliographic coordinates and areas, is
available to the public.
