It changes with temperature and with barometric pressure.

I have also an audible altimeter.

My only instruments are an altimeter and time.

ERS 1 radar altimeter data provide worldwide surface information.

PRARE on ERS 2 provides precise corrections of altimeter measurements.

The satellite uses a radar altimeter to yield precise measurements of sea surface height.

What you just heard are the interactions of barometric pressure, wind and temperature readings that were recorded of Hurricane Noel in 2007.

What you just heard are the interactions of barometric pressure, wind and temperature readings that were recorded of Hurricane Noel in 2007.

The radar altimeter permits the measurement of wind speed, wave height, sea surface elevation, ice profile, land and ice topography, and sea ice boundaries.

The ATSR Microwave Sounder is a dual frequency passive radiometer, whose data are used primarily to correct radar altimeter measurements and to determine the atmospheric vapour content.

The precise range and range rate equipment (PRARE), operational on ERS 2, allows precise orbit calculations to be made and accurate corrections to radar altimeter measurements to be implemented.

The payloads of the satellite segment of both systems would be designed to monitor the land and ocean environment, the geosphere, hydrosphere and meteorological conditions, with the aid of visible, near infrared, microwave, short wave and thermal radiometers, synthetic aperture radar, radar altimeter and scattering lidar.

11. The principal instruments on board the satellites include (a) an Active Microwave Instrument (AMI), which comprises a synthetic aperture radar (SAR) and a wind scatterometer (b) a radar altimeter (RA) (c) an along track scanning radiometer (ATSR), which comprises an infrared radiometer (IRR) and a microwave sounder (MWS) (d) precise range and range rate equipment (PRARE), presently functioning only on ERS 2 and (e) a laser retroreflector.