# Radar altimetry - sea surface height and inland water levels
*methodologies*

Measures sea surface height, significant wave height, and inland water levels from nadir-pointing radar pulse returns; good for sea level rise monitoring, ocean circulation, and river/lake hydrology.

## Specifications
- **family**: Radar altimetry
- **requirements envelope**: {"kind":"geometric","gsd_max":300000,"repeat_pass_geometry":true,"polarisation_modes":["Ku-band"]}
- **entity type**: methodology
- **last verified date**: 2026-05-22
- **verified by**: sw
- **claim status**: unclaimed
- **attributes**: {"family":"Radar altimetry","summary":"Measures sea surface height, significant wave height, and inland water levels from nadir-pointing radar pulse returns; good for sea level rise monitoring, ocean circulation, and river/lake hydrology.","requirements_envelope":"{\"kind\":\"geometric\",\"gsd_max\":300000,\"repeat_pass_geometry\":true,\"polarisation_modes\":[\"Ku-band\"]}"}
- **technology**: radar

## Editorial
Nadir pulse-limited or SAR-mode altimeter measures round-trip travel time to the surface. Corrections applied for ionosphere, wet/dry troposphere, and tides. TOPEX/Poseidon -> Jason-1/2/3 -> Sentinel-6 constitutes an unbroken record since 1992. [Wikipedia: Radar altimeter](https://en.wikipedia.org/wiki/Radar_altimeter)

## Sources
- [wikipedia] | Wikipedia: Radar altimeter | https://en.wikipedia.org/wiki/Radar_altimeter | tier=community | accessed=2026-05-22

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Source: https://eo-atlas.org/methodologies/radar-altimetry
Maintainer: SpectraWorks B.V. (CC-BY 4.0)