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The CTOH computes regional along-track sea level anomaly (SLA) products for the following altimeter missions: Topex/Poseidon, Jason-1, Jason-1 interleaved, Topex/Poseidon interleaved, Jason-2, Jason-3, Geosat Follow on (GFO), SARAL/Altika and Envisat.  Long time series of SLA combining altimeter data from T/P, Jason-1 and Jason-2 are also available.  Table 1 indicates for each satellite mission and/or regional product the first and last dates available (and the corresponding cycle number).


Mission Start End
T/P+J1+J2+J3 1993/02/28 (17 of T/P) 2020/06/02 (158 of Jason-3)
Envisat-v2.1 2002/10/01 (10) 2010/09/14 (92)
GFO 2000/01/08 (37) 2008/09/08 (222)
T/P interleaved+Jason-1 interleaved 2002/09/21 (369 of T/P interleaved) 2012/02/02 (372 of Jason-1 interleaved)
SARAL/Altika 2013/03/04 (1) 2016/04/07 (32)

Table 1: temporal availability of each time series

Using the GDR (Geophysical Data Record) data and additional altimetry corrections available in the CTOH database (see Processing method for details), SLA projected onto reference tracks with a spatial interval of about 6-7 km between points (1 second) are computed using the X-TRACK software (Birol et al., 2017), developed at LEGOS. The processing is done on a regional basis and for each region the along-track SLA is available.


Publications should include the following statement in the Acknowledgments:
“Altimetry data used in this study were developed, validated, and distributed by the CTOH/LEGOS,
X-TRACK products are now identified by a DOI. Please use it when citing X-TRACK.
For the last version the DOI is 10.6096/CTOH_X-TRACK_2017_02.


Product content:


The product available in a number of different regions (see map) consists in 1-Hz alongtrack SLA time series reprocessed on a regional basis with the X-TRACK software. Two versions exist: one with the raw SLA and one with the spatially filtered SLA. It is provided in NetCDF format and includes: 

  • the SLA data along a nominal ground-track, 
  • an alongtrack MSSH profile which is consistent with the SLA (same period of data), 
  • the geophysical corrections (the X-TRACK tidal and X-TRACK DAC corrections are already applied on SLA but are provided in separate fields for information)
  • the distance to nearest coast from GSHHS (Wessel et al., 1996),
  • the distance to nearest coast from P.Stumpf (Stumpf and Potemra, 2012) and
  • the mean dynamic topography CNES_CLS_09 (Rio et al., 2011)

Further information:



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