  We introduce WECS (Wavelet Energies Correlation Sreening), an unsupervised
sparse procedure to detect spatio-temporal change points on multi-temporal SAR
(POLSAR) images or even on sequences of very high resolution images. The
procedure is based on wavelet approximation for the multi-temporal images,
wavelet energy apportionment, and ultra-high dimensional correlation screening
for the wavelet coefficients. We present two complimentary wavelet measures in
order to detect sudden and/or cumulative changes, as well as for the case of
stationary or non-stationary multi-temporal images. We show WECS performance on
synthetic multi-temporal image data. We also apply the proposed method to a
time series of 85 satellite images in the border region of Brazil and the
French Guiana. The images were captured from November 08, 2015 to December 09
2017.
