SLA 1Hz Products

Alongtrack Sea Level Anomalies - Regional Products


X-TRACK products are now available on the Aviso+ website


NEWS 2020 :

  • Extension of TP+J1+J2+J3 time series, up to May 2019.
  • MDT CNES_CLS 18 add in TP+J1+J2+J3 files

The CTOH computes and distributes specific, coastal along-track sea level anomalies (SLA) using its X-TRACK processor for all precise altimeter missions : Topex/Poseidon (TP), Jason-1 (J1) , Jason-1 interleaved (J1N), Topex/Poseidon interleaved (TPN), Jason-2, Geosat Follow on (GFO), Envisat and Saral/Altika (click here to view available missions and the temporal coverage of each one).

Using the latest corrections available in the CTOH database, CTOH computes a coastally-adapted Sea Surface Height (SSH) along the satellites ground-track for each cycle. Additionnal geophysical corrections are applied accounting for the aliasing of tides and short-term atmopheric effects in the SSH measurements. Details on selected corrections are given here. The Mean Sea Surface (MSSH) is computed at each point, based on the mission period currently available, and subtracted from the corrected SSH in order to form the SLA. The SLA are finally projected onto a reference track with a spatial interval of about 7 km between points (1 second).

For every region highlighted on the map below, the CTOH distributes both the raw SLA and a 40-km along-track filtered SLA product (click on the map to view regional details).

PLEASE Note that the connection between the time series from Topex/Poseidon, Jason-1 and Jason-2 (and now Jason-3) is done by addind a "simple" mean bias between the different missions (the values are the same than the one recommended by AVISO and are derived from the difference of the averages of the global MSL between two missions on a common period). In consequence we suspect that this type of combination is too simple to derive very precise long-term sea level tendencies from the X-TRACK products.



Please do not forget to mention the following sentence in all publications or communications referring to a work based on the CTOH/LEGOS altimetry dataset:
"Altimetry data used in this study were developed, validated, and distributed by the CTOH/LEGOS, France".
A DOI (Digital Object Identifier) is now attached to X-TRACK products; please use it when referring to it in publication.


Data use conditions

Data release:
  • CTOH_X-TRACK_2015_01
  • CTOH_X-TRACK_2017_01
  • CTOH_X-TRACK_2017_02

When clicking on the image below you will be redirected to our Aviso+ web page where more information can be found.

World map of X-TRACK regional polygons (from 2016)

short name long name
adelie Adelie-Mertz
amazon Amazon 
asa  Atlantic South America 
chinasea  China Sea
drake  Drake passage 
eaustralia  East Australia
gom  Gulf of Mexico - Caribbean Sea
gulfstream  Gulf Stream
hudson  Hudson Bay
humboldt  Humboldt current
kerguelen  Kerguelen Islands 
labrador  Labrador Sea 
medsea  Mediterranean Sea 
nea  North East Atlantic 
nindian  North Indian Ocean 
norway  Norway 
nwa  North West America 
nwp  North West Pacific 
sea  South and East Africa 
wafrica  West Africa
waustralia  West Australia
wla  West Latin America - California 
wtp  West Tropical Pacific

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