Landtrendr的原理图
APP（https://emaprlab.users.earthengine.app/view/lt-gee-pixel-time-series）
Bfast原理
（http://bfast.r-forge.r-project.org/）
APP（https://andreim.users.earthengine.app/view/bfastmonitor）
Fitted seasonal, trend and remainder (i.e. estimated noise) components for a 16-day MODIS NDVI time series (data series) of a pine plantation in the northern part of the study area. Three abrupt changes are detected in the trend component of the time series. Time (- - -), corresponding conidence interval (red), direction and magnitude of abrupt change and slope of the gradual change are shown in the estimated trend component. The solid bars on the right hand side of the plot show the same data range, to aid comparisons.
Simulated 16-day MODIS NDVI time series. The period from 2004 until mid-2010 (i.e., the time step just before the simulated break), is considered the history period and the period after the simulated break is the monitoring period (grey background). The monitoring period contains 6 observations. The result of the monitoring approach is shown: A stable history period is identified within the history period (i.e., 2007 until mid-2010) and used to model and predict the normal data variation (blue dashed line) to enable disturbance detection. Here, a disturbance is detected after 3 observations in the monitoring period (green vertical line)."