R Package for harmonic modelling of time-series data

R Package for harmonic modelling of time-series data

April 23, 2020

Sentinel-2 NDVI time-series over the Steigerwald. Left: Original satellite scenes after cloud, cloud shadow and snow maksing. Right: Interpolated time-series using a harmonic modelling.

In order to fully exploit the monitoring potential of the satellite systems, challenges such as noise and data gaps must be effectively addressed. These quality losses are mainly caused by sensor artifacts, clouds, cloud shadows and other weather conditions (Verbesselt et al., 2012). In the context of time series analysis, harmonic modeling is a powerful tool to fill these gaps and reduce noise by smoothing the original signal (de Jong et al., 2011).

For that purpose, I created an R-package rHarmonics which enables the user to perform a harmonic analysis on a given time-series data set.

To calculate the harmonic fitted curve of a periodic signal, ordinary least squares regressions are computed using coupled sine and cosine curves on time-series data. The underlying algorithm which is based on Shumway & Stoffer (2017) equations 4.1 – 4.2 can be seen below:

MODIS NDVI time-series data together with a harmonic fitted curve using 3 cylces per year.



Literature:

de Jong, R., de Bruin, S., de Wit, A., Schaepman, M. E., & Dent, D. L. (2011). Analysis of monotonic greening and browning trends from global ndvi time-series. Remote Sensing of Environment, 115 (2), 692–702.

Shumway, R. H., & Stoffer, D. S. (2017). Time series analysis and its applications: with r examples. Springer.

Verbesselt, J., Zeileis, A., & Herold, M. (2012). Near real-time disturbance detection using satellite image time series. Remote Sensing of Environment, 123 , 98–108.

you may also like:

EORC board meeting 2025

EORC board meeting 2025

This week, the annual board meeting of our EORC (Earth Observation Research Cluster) took place, bringing together the members to discuss and deliberate on several strategic and organisational issues. The meeting served as a platform for board members to share...

Congratulations to Alexandra Bell on Her Successful PhD Defense!

Congratulations to Alexandra Bell on Her Successful PhD Defense!

We are pleased to congratulate Alexandra Bell on the successful defense of her PhD thesis, which explored the role of Earth Observation (EO) data in political decision-making. In her research, Alexandra examined how EO technologies interact with political processes,...

New PhD student Lukas Block

New PhD student Lukas Block

We are pleased to welcome Lukas Block as a new PhD student.  Lukas holds a Master's degree in Geological Sciences from the Free University of Berlin, where he investigated the stratigraphic record of the Anthropocene in lacustrine sediments. He has gained...

Press Release by University of Würzburg about our Arctic research

Press Release by University of Würzburg about our Arctic research

Our work in the Arctic on Svalbard was covered by the press team of the University of Würzburg. It covers our focus on studying the region’s ecosystems and the effects of climate change on its environment using Earth Observation methods. Please see the german version...

Prof Gustau Camps-Valls visits DLR-EOC

Prof Gustau Camps-Valls visits DLR-EOC

Today we had the great pleasure to welcome Prof Gustau Camps-Valls at DLR's Earth Observation Center (EOC).   Prof Gustau Camps-Valls is a Full Professor in Electrical Engineering and leads the Image and Signal Processing (ISP) group at Universitat de València (...