Anomaly Detection and Classification in Multispectral Time Series Based on Hidden Markov Models

Kareth M. León-López (1) , Florian Mouret (2, 3, 4) , Henry Arguello (1) , Jean-Yves Tourneret (3, 4)

1 UIS - Universidad Industrial de Santander [Bucaramanga]
2 TerraNIS
3 Toulouse INP - Institut National Polytechnique (Toulouse)
4 IRIT-MINDS - CoMputational imagINg anD viSion

Monitoring agriculture from satellite remote sensing data, such as multispectral images, has become a powerful tool since it has demonstrated a great potential for providing timely and accurate knowledge of crops. Detecting anomalies in time series of multispectral remote sensing images for crop monitoring is generally performed using a large sample of historical data at a pixel level. Conversely, this article presents a framework for anomaly detection (AD), localization, and classification that exploits the temporal information contained in a given season at a parcel level to detect and localize outliers using hidden Markov models (HMMs). Specifically, the AD part is based on the learning of HMM parameters associated with unlabeled normal data that are used in a second step to detect abnormal crop parcels referred to as anomalies. The learned HMM can also be used in time segments to temporally localize the anomalies affecting the crop parcels. The detected and localized anomalies are finally classified using a supervised classifier, e.g., based on support vector machines. The proposed framework is applicable to images partially covered by clouds and can handle a set of crop parcels acquired in the same season bypassing problems due to crop rotations. Numerical experiments are conducted on synthetic and real data, where the real data correspond to vegetation indices extracted from several multitemporal Sentinel-2 images of rapeseed crops. The proposed approach is compared to standard AD methods yielding better detection rates with the advantage of allowing anomalies to be localized and characterized.

Mots clés: Agricultural monitoring; anomaly classification; anomaly detection (AD); hidden Markov models (HMMs); remote sensing; time series; Anomaly detection; Hidden Markov models; agricultural monitoring; semi-supervised learning

Domaines: Sciences de l'ingénieur [physics]; Informatique [cs]

Kareth M. León-López, Florian Mouret, Henry Arguello, Jean-Yves Tourneret. Anomaly Detection and Classification in Multispectral Time Series Based on Hidden Markov Models. IEEE Transactions on Geoscience and Remote Sensing, 2022, 60, pp.1 - 11. ⟨10.1109/tgrs.2021.3101127⟩. ⟨hal-03857425⟩