1 Introduction

The following workflow can be used to extract a time series of Landsat Normalized Burn Ratio (NBR) using Google Earth Engine and the LandTrendr change detection algorithm.1 See (1.1) for a definitions of the spectral change metrics extracted via Landtrendr.

The workflow presented was developed and provided to me by Jen Hird (University of Calgary | Alberta Biodiversity Monitoring Institute, 2020). I adapted it for chapter 3 of my PhD thesis.

The following code javascript and r code are used in this workflow:

Google Earth Engine Lnadtrendr script

Download all2017HAs_UpdatedBatchReformattingScript_20200204.R

Table 1.1: NBR metric descriptions
metric description
preDistMean For each polygon, the average NBR value for the 5 years pre-disturbance
yod_mean Year of disturbance
eoc_year year when NBR values started to increase
totDistb Difference between pre-disturbance NBR and the NBR at the start of regeneration
relDistbVal_mean (totDistb)/SQRT(ABS(preDistMean/1000)) Calculation from @MillerThode2007
regen5yr, regen10yr, regen15yr, regen20yr Percent of totDistb values regained after 5, 10, 15, and 20 years after the disturbance
yrTo30, yrTo50, yrTo80, yrTo100 Time taken for 30%, 50%, 80%, and 100% of thetotDistb to be regained
regen_survey Percent of totDistb values regained at the year of the bird survey.
lengthDistb time between yod and eoc
length of Regen end year - eocYr
TOT_PIXELS number of pixels used for change detection (Landsat has a 30m resolution)
PERC_UNMSKD percent of pixels not masked by clouds or atmospheric conditions

References

1.
Kennedy, R. E. et al. Implementation of the LandTrendr algorithm on Google Earth Engine. Remote Sensing 10, 691 (2018).