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Assessment of an optimal parameter space for spatial cluster detection of SMEAR Estonia flux footprint data using unsupervised learning algorithms Cover

Assessment of an optimal parameter space for spatial cluster detection of SMEAR Estonia flux footprint data using unsupervised learning algorithms

Open Access
|Mar 2026

Figures & Tables

Figure 1.

We filtered the calculated results to match the number of clusters ranging between 2 and 6, a silhouette score above 0.3, the minimum samples (minPts) in the range of 10 to 20, and the Davies-Bouldin score below 3.5. Marginal distributions of the hyper-parameters are shown atop and right.

Figure 2.

Example of clusters detected among data for July 2015 with parameters ϵ = 0.3 and minPts = 15. Panel A shows the data scaled by the RobustScaler function and the color denotes the number of points per grid cell with a darker color for higher frequency. Panel B shows the estimated clusters using HDBSCAN, and C by DBSCAN. Note: The order in cluster labelling is different for the algorithms and therefore the coloring differs.

Figure 3.

Example of clusters detected among data for July 2017 with parameters ϵ = 0.15 and minPts = 17. The panels follow the logic given in Figure 2.

Summary of the parameters obtained from applying clustering algorithms to the strongest signal location within the SMEAR Estonia footprint_ The averages and standard deviations of discrete variables have been rounded to the nearest integer_ The execution time is measured in seconds per iteration_

ScalerDBSCANHDBSCAN
StandardRobustStandardRobust
ϵ0.48 ± 0.230.48 ± 0.230.26 ±0.140.23 ± 0.14
minPts25 ± 1425 ± 1431 ± 1231 ± 12
Clusters (min. max)3 ± 10 (0. 285)2 ± 6 (0. 293)3 ± 1 (0. 25)3 ± 1 (0. 20)
Outliers169 ± 256107 ± 202224 ± 126209 ± 132
(min. max)(0.1274)(0. 1195)(3. 938)(3. 963)
Silhouette score0.31 ± 0.200.36 ±0.190.27 ± 0.140.30 ±0.15
Davies-Bouldin score3.38 ± 6.993.35 ± 8.223.03 ±5.112.8 ± 1.6
Execution time in s/it8.37.36.55.6
DOI: https://doi.org/10.2478/fsmu-2025-0002 | Journal eISSN: 1736-8723 | Journal ISSN: 1406-9954
Language: English
Page range: 20 - 27
Submitted on: May 4, 2025
Accepted on: Jan 18, 2025
Published on: Mar 23, 2026
In partnership with: Paradigm Publishing Services
Publication frequency: 2 issues per year

© 2026 Steffen M. Noe, Anuj Thapa Magar, Emílio Graciliano Ferreira Mercuri, published by Estonian University of Life Sciences
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.