ISSN 2070-7401 (Print), ISSN 2411-0280 (Online)
Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa
CURRENT PROBLEMS IN REMOTE SENSING OF THE EARTH FROM SPACE

  

Sovremennye problemy distantsionnogo zondirovaniya Zemli iz kosmosa, 2024, Vol. 21, No. 1, pp. 76-87

Statistical and machine learning methods for river water level time series construction using satellite altimetry

N.K. Semenova 1, 2 , E.A. Zakharova 1, 3 , I.N. Krylenko 1, 2 , A.A. Sazonov 1, 2 
1 Water Problems Institute RAS, Moscow, Russia
2 Lomonosov Moscow State University, Moscow, Russia
3 Earth Observation for Learning and Application, Toulouse, France
Accepted: 08.12.2023
DOI: 10.21046/2070-7401-2024-21-1-76-87
The use of satellite altimetry data for monitoring the level regime of rivers in Arctic regions is limited due to the negative effect of complex fluvial morphology and ice cover on altimetric radar measurements. The construction of time series of river water levels consists of two main stages: 1) accurate geographic sampling of satellite measurements over the river channel and 2) calculation of the average level for a given date after filtering outliers. This work is based on measurements from the European altimetry satellites Sentintel-3A and Sentinel-3B. The paper proposes a method for determining aberrant values of altimetric measurements (outliers) over the wide floodplain section of the Kolyma River. The method improved the accuracy of calculation of satellite time series of water level by 0.04–1.59 m (or 4–85 %) compared to the widely used standard statistical method of filtering altimetric measurements. The suggested method is based on the combination of three algorithms of different complexity: statistical (Mahalanobis distance), clustering (Density-Based Spatial Clustering of Applications with Noise (DBSCAN)) and machine learning (Isolating Forest) methods. In the combined approach, values classified as outliers by at least two algorithms were considered outliers. This approach allowed us to reduce the impact of potential individual shortcomings of each of the three methods.
Keywords: satellite altimetry, Arctic rivers, water level, detection of outliers, machine learning methods
Full text

References:

  1. Zakharova E. A., Krylenko I. N., Sazonov A. A., Semenova N. K., Lisina A. A., Water level regime of Arctic rivers according to modeling and satellite measurements, Meteorologiya i gidrologiya, 2023, No. 12, pp. 115–124 (in Russian).
  2. Abdalla S., Kolahchi A. A., Ablain M. et al., Altimetry for the future: Building on 25 years of progress, Advances in Space Research, 2021, Vol. 68, pp. 319–363, DOI: 10.1201/9781315151779-5.
  3. ATBD: Algorithm Theoretical Basis Document, Deliverable D1.3, Sentinel-3 and Cryosat SAR/SARin Radar Altimetry for Coastal Zone and Inland Water, ESA Contract, 2022, 4000129872/20/I-DT, 123 p.
  4. Biancamaria S., Schaedele T., Blumstein D. et al., Validation of Jason-3 tracking modes over French rivers, Remote Sensing of Environment, 2018, Vol. 209, pp. 77–89, DOI: 10.1016/j.rse.2018.02.037.
  5. Liu F. T., Ting K. M., Zhou Z. H., Isolation Forest, 8 th IEEE Intern. Conf. Data Mining (ICDM’08), 2008, pp. 413–422, DOI: 10.1109/ICDM.2008.17.
  6. Maillard P., Bercher N., Calmant S., New processing approaches on the retrieval of water levels in Envisat and SARAL radar altimetry over rivers: A case study of the Sao Francisco River, Brazil, Remote Sensing of Environment, 2015, Vol. 156, pp. 226–241, DOI: 10.1016/j.rse.2014.09.027.
  7. Rémy F., Flament T., Blarel F., Benveniste J., Radar altimetry measurements over Antarctic ice sheet: a focus on antenna polarization and change in backscatter problems, Advances in Space Research, 2012, Vol. 50, pp. 998–1006, DOI: 10.1016/j.asr.2012.04.003.
  8. Schubert E., Sander J., Ester M., Kriegel H.-P., Xu X., DBSCAN Revisited, Revisited: Why and How You Should (Still) Use DBSCAN, ACM Trans. Database Systems, 2017, Vol. 42, pp. 1–21, DOI: 10.1145/3068335.
  9. Schwatke C., Dettmering D., Bosch W., Seitz F., DAHITI — an innovative approach for estimating water level time series over inland waters using multi-mission satellite altimetry, Hydrology and Earth System Sciences, 2015, Vol. 19, pp. 4345–4364, DOI: 10.5194/hess-19-4345-2015.
  10. Zakharova E., Nielsen K., Kamenev G., Kouraev A., River discharge estimation from radar altimetry: Assessment of satellite performance, river scales and methods, J. Hydrology, 2020, Vol. 583, Article 124561, DOI: 10.1016/j.jhydrol.2020.124561.