iDOT.readme.txt                                      October 2011

The "profile approach", developed by Bosch & Savcenko (2010) estimates 
the dynamic ocean topography (DOT) along individual profiles observed 
by nearly all satellite altimeter missions operating since end of 1992. 
The instantaneous DOT profiles (iDOT) are derived as deviation between 
the actual sea surface heights h and the geoid heights N which realize 
over ocean surface an equipotential surface of the GOCO02S Earth gravity 
field model (Goinginger et al. 2011). 

Both, h and N are consistently filtered by a Gauss-type filter with a 
half width of 69 km. For more details see Bosch et al. (2012), Bosch & Savcenko (2010). 
This way, the iDOT profiles realize smoothed snapshots of the ocean 
topography and may be used to characterize the temporal evolution of 
the DOT since late 1992. Moreover, as the data of all satellite altimeter 
missions have been carefully harmonized and cross-calibrated in advance 
(e.g. Dettmering & Bosch 2010), it should be possible to merge and combine 
iDOT profiles of any mission in order to improve the spatial and 
temporal resolution. Due to the filter length of 69 km the IDOT profiles
carry the signature of meso-scale pattern and can be taken to illustrate
evolution and kinematics of Eddies and of the geostrophic velocity field
(see animations at http://www.dgfi.badw.de/?333 )

The iDOT-profiles are distributed here in the hope that they will be useful, 
but DGFI provides these data “as is” without warranty, expressed or 
implied, as to the use or appropriateness of the iDot-profiles, and 
there are no warranties of merchantability or fitness of these data 
for a particular purpose or use. 

The iDOT data is structured according to the hierarchy

  mission  1:n    cycle    1:m    pass 
  
and is available  on the anonymous ftp

   ftp://ftp.dgfi.badw.de
   
in directory

   pub/iDOT/gaussFilter.69km
   
for Envisat, ERS-1, ERS-2, Topex, Topex-EM, Poseidon, Jason-1, Jason1-EM, 
Jason-2 and GFO.
The pass files follow the naming convention  ccc.idot.69.nc where ccc 
stands for the cycle. The pass files are given in netcdf (Network Common 
Data Form), a self-describing, machine-independent data format developed 
by unidata (see http://www.unidata.ucar.edu/software/netcdf/ )

References:  
Bosch W., R. Savcenko, D. Dettmering, and Ch. Schwatke (2012) A two decade
   time series of eddy-resolving dynamic ocean topography (iDOT). Proceedings
   of the ESA symposium on 20 Years of Progress in Radar Altimetry, Venice, 
   ESA Special Publication SP710 (in press)
Bosch W., Savcenko R.: On Estimating the Dynamic Ocean Topography. 
   In: Mertikas S.P. (Ed.): Gravity, Geoid and Earth Observation. 
   Springer IAG Symposia, Vol. 135, 263-269 , 2010 
Bosch W., Savcenko R., Luz R. T.: The absolute dynamic ocean topography 
   (ADOT) – estimation and application. Proceedings of the ESA Living 
   Planet Symposium, Bergen, Norway, ESA Publication SP-686 (CD-Rom), 2010 
Dettmering D. and W. Bosch. „Global Calibration of Jason-2 by Multi-Mission 
   Crossover Analysis“. Marine Geodesy 33, Nr. sup1 (2010): 150–161.
Goiginger H., et al.: The combined satellite-only global gravity field 
   model GOCO02S. Presented at the 2011 General Assembly of the European 
   Geosciences Union, Vienna, Austria, April 4-8, 2011.