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Altimeter along-track (L2P) data

GlobWave offers free access to 9 geophysical quality and 3 real-time altimeter data streams from 9 satellites stretching back as far as 1985 with GEOSAT in an homogenenous and consistent format and content.

Altimeter-data

An altimeter is a nadir pointing pulse radar designed to measure the echoes from ocean and ice surfaces. Over the ocean, it is used to measure wave height, wind speed and sea-surface elevation, the latter of which is appropriate to the study of ocean currents, th

e tides and the global geoid. On-board processing to the return echoes from sea surfaces provides the time delay, waveform slope and power level several times per second. These measurements are averaged during the data processing to typically yield one-second mean values. Quasi real-time estimates of ocean parameters are therefore possible. Altitude measurements are obtained from the time delay between transmission and reception of a pulse, after correction for atmospheric and other effects. Significant Wave Height is measured from the slope of the leading edge of the return. Wind speed over sea surfaces and sea/ice boundary location is derived from the power level of the return signal.

 

 

Altimeter products summary

GlobWave altimeter come in two different product lines, for which data from several altimeter missions are provided :

  • real-time products, available for still ongoing missions within a few hours after acquisition (usually about 3 hours) for operational applications such as wave forecasting
  • geophysical products, available usually a few weeks or months (or years in case of reprocessing) after acquisition. These are the best quality data and should be used when real-time data are not necessary. The globwave archive for these products is updated every 6 months.

Geophysical products

Product Id

Source L2 product

Mission

Coverage

GW_L2P_ALT_ERS1_GDR

OPR v6 (ESA/Ifremer)

ERS-1

GW_L2P_ALT_ERS2_GDR

OPR v6 (ESA/Ifremer)

ERS-2

GW_L2P_ALT_ENVI_GDR

GDR (ESA)

Envisat

GW_L2P_ALT_GFO_GDR

GDR (US Navy)

GEOSAT Follow on

GW_L2P_ALT_GEOS_GDR

GDR (US Navy)

GEOSAT

GW_L2P_ALT_TOPX_GDR

GDR (CNES/NASA)

Topex/Poseidon

GW_L2P_ALT_JAS1_GDR

GDR (CNES/NASA)

Jason 1

GW_L2P_ALT_JAS2_GDR

GDR (CNES/NASA)

Jason 2

GW_L2P_ALT_CRYO_GDR

IGDR (ESA/NOAA)

CryoSAT

Real-time products

Product Id

Source L2 product

Mission

Coverage

GW_L2P_ALT_JAS1_NRT

OGDR (CNES/NASA)

Jason 1

GW_L2P_ALT_JAS2_NRT

OGDR (CNES/NASA)

Jason 2

GW_L2P_ALT_ENVI_NRT

FGDR (ESA)

Envisat

How I do I get access to the data? The data is hosted on an ftp site. Username and password details can be obtained by e-mailing the CERSAT Help Desk at This email address is being protected from spambots. You need JavaScript enabled to view it. with the subject: GlobWave Data Access. We recommend that you consult sections 3 and 4.4.6 of the Product User Guide regarding essential information and known issues respectively. If you already have a username and password then you can browse the data on the ftp site by clicking here.