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🛰 Satellite(s)

e.g., Sentinel-3.

📊 Monitoring element

Surface water reflected echo of microwave pulse.

🧰 Description technique

Jiang et al. (2020) conducted a comprehensive evaluation of Sentinel-3A water surface elevation data at 50 virtual stations located on a wide range of rivers in China.

📏 Accuracy / Resolution

RMSE: 0.12-0.9m for plain areas.

🗺 Case study

Chinese rivers (Jiang et al. 2020).

Tip

Benefits

Thanks to the finer along-track resolution, SAR altimetry is less influenced by land contamination, islands, etc. compared to conventional low resolution mode (LRM) altimetry, especially in coastal areas

Note

Limitations

  • Application of S3A over mountain rivers still requires careful evaluation, especially before March 2019.

  • The ability to measure river stage depends on the altimeter's tracking function.

  • Re-tracking approaches should be take into account the river width, flow direction relative to the orbit orientation, and surrounding terrain

Info

Applicability for Northland

Yes, seems likely.

DEM inputs would help altimeter's tracking function. Some trials to test local parameters (rivers and topography features) could be undertaken. Also it would be required to check if accuracy would be fit for purpose for small rivers.Techniques applying optical data will be limited in coverage and temporal granularity by the persistent cloud cover in the region, particularly during the winter months. Mature cloud-masking techniques are directly available for open access multispectral data (e.g. Landsat and Sentinel-2). When using commercial data, care must be taken to ensure that there is sufficiently cloud free imagery available, as cloud masking is not as mature, and ordering a large volume of imagery to ensure complete cloud free coverage between multiple observations can become cost prohibitive.

Publication references

📚 Jiang L, Nielsen K, Dinardo S, Andersen OB, Bauer-Gottwein P. 2020. Evaluation of Sentinel-3 SRAL SAR altimetry over Chinese rivers. Remote Sensing of Environment. 237:111546. doi:10.1016/j.rse.2019.111546.

🔗 https://orbit.dtu.dk/en/publications/evaluation-of-sentinel-3-sral-sar-altimetry-over-chinese-rivers

(info) Other comments or information

Sentinel-3 is the first radar altimetry mission operating with a synthetic aperture radar (SAR) altimeter at global scale and with a new on-board tracking system (i.e. open-loop), which has great potential in terms of delivering reliable observations of inland water bodies for the next two decades (several future missions include an open-loop tracking mode).

Other references

📚 Normandin, C., Frappart, F., Diepkilé, A.T., Marieu, V., Mougin, E., Blarel, F., Lubac, B., Braquet, N., Ba, A., 2018. Evolution of the performances of radar altimetry missions from ERS-2 to Sentinel-3A over the Inner Niger Delta. Remote Sens. 10, 833.

🔗 http://doi.org/10.3390/rs10060833

📚 Dinardo, S., Fenoglio-Marc, L., Buchhaupt, C., Becker, M., Scharroo, R., Joana Fernandes, M., Benveniste, J., 2018. Coastal SAR and PLRM altimetry in German Bight and West Baltic Sea. Adv. Space Res. 62, 1371–1404. https://doi.org/10.1016/j.asr.2017.12.018

📚 Biancamaria, S., Schaedele, T., Blumstein, D., Frappart, F., Boy, F., Desjonquères, J.D., Pottier, C., Blarel, F., Niño, F., 2018. Validation of Jason-3 tracking modes over French rivers. Remote Sens. Environ. 209, 77–89. https://doi.org/10.1016/j.rse.2018.02.037

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