Monitoring Trees Using Data from Satellites and Analysis of Spectral Reflectance (Opinion After Waiting for 3 Years)

This is a continuation (part three) of these blogposts made in May 2017:
http://openplants.blogspot.com/2017/05/monitoring-at-risk-trees-using-spectral.html
http://openplants.blogspot.com/2017/05/bogstadveien-19-oslo-norway.html

That blogspot discussed a method whereby data were collected by satellites and processed by remote-sensing software to generate spectral reflectance of trees. The spectral reflectance could, as the service provider postulated, correlate to tree stress and/or structural stability.

In one back-dated analysis, the spectral reflectance of three (3) trees were analysed from data collected on 2 Sep 2014 and 8 Sep 2015 (one year apart) from the WorldView2 satellite. One of the three trees had felled without human intervention on 10 Aug 2016.

As the service provider wrote in the article (see Reference) - in just one year, the drop in the spectral reflectance of the near-infrared band for Fallen Tree #1 was 5%. There was not much variation in spectral reflectance in the adjacent Alive Tree #2 and Alive Tree #3.

HOWEVER, Tree #1 did not fall, as seen in the Google Streetview dated May 2016 and Sep 2019.

This photo showed that Tree #2 was the one that felled, as it was present before it felled on 10 Aug 2016, and was not present on Sep 2019. Tree #2 was peeking out from behind of Tree #1 (indicated by red arrow and not a large branch of Tree #1). (Source: Google Streetview)

Further confirmation that Tree #2 was the one that felled. (Source: Google Maps)

Therefore, as suspected in this post in May 2017 (http://openplants.blogspot.com/2017/05/bogstadveien-19-oslo-norway.html), Tree #1 was indeed mislabelled, and the data and subsequent spectral reflectance analysis may be unreliable to be correlated to tree stress and/or structural stability.

Reference:
International Society of Arboriculture's Arborist News, Volume 26, Number 2, April 2017