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LandTrendr and TimeSync: Update on new tools to tap the archive. LandTrendr: Robert E. Kennedy, Zhiqiang Yang, Warren B. Cohen TimeSync: Warren B. Cohen, Zhiqiang Yang, Robert E. Kennedy. Landsat Science Team Meeting January 2009.

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landtrendr and timesync update on new tools to tap the archive

LandTrendr and TimeSync:Update on new tools to tap the archive

LandTrendr: Robert E. Kennedy, Zhiqiang Yang, Warren B. Cohen

TimeSync: Warren B. Cohen, Zhiqiang Yang, Robert E. Kennedy

Landsat Science Team Meeting January 2009

landtrendr landsat based detection of trends in disturbance and recovery
LandTrendr: Landsat-based Detection of Trends in Disturbance and Recovery

Steps in the LandTrendr process

Evaluate veracity of selected events: TimeSync

Prepare stack of yearly imagery

Extract summary information from segments

Extract spectral trajectories for pixels

Statistically identify and fit segments with consistent trends

Kennedy et al. LandTrendr

outputs diversity of disturbance and regrowth processes

Partial

Fast

Vegetation canopy removal

Vegetation canopy recovery

Full

Slow

Outputs – Diversity of Disturbance and Regrowth Processes

High intensity, short duration

Dramatic events (clearcuts, fires) more often -- commensurate with climatic, economic, & ecological cycles

Slow processes such as growth and recovery as well as insect and drought-related mortality, through use of trajectory approach

Low intensity, long duration

Annual resolution

More subtle events (thinning, partial burns) due to increased signal-to-noise ratio and use of trajectory approach

Low intensity, short duration

Kennedy et al. LandTrendr

current landtrendr mapping
Current LandTrendr Mapping
  • LandTrendr mapping:
    • Northwest Forest Plan (NWFP) update - western WA and OR (Jan 2009)
    • ORCA II -- Carbon modeling and integration - Southern California (Spring 2009)
    • National Parks (2008-2009)
    • Idaho and Colorado insect outbreaks (Spring 2009)
    • OWEB - link disturbance to coupled forest/hydrological models (Spring 2009)
    • All of CA, WA, OR to follow

Kennedy et al. LandTrendr

timesync synching automated and human interpretations of landsat time series

TimeSync: Synching Automated and Human Interpretations of Landsat Time Series

Use good, old-fashioned photo-interpretation skills, but applied to “plots” within Landsat time series

Examine spectral trajectories and identify temporal vertices & segments

timesync

TimeSync

Any band or index

Populate database with observations

Sample design for “validation”

timesync7

TimeSync

Reality check against recent Google Earth image

Compare with other databases (harvest records, fire catalogs), as available

timesync8

TimeSync

Complicated, but intuitive, effective process

Applicable to any Landsat time series

Variety of applications (exploration, calibration, validation)

timesync9

e.g., disturbance agreement (%) as a function of TimeSync- observed disturbance agent and relative intensity.

TimeSync

Summarize agreement with LandTrendr map output…

landtrendr beyond change detection
LandTrendr: Beyond change detection
  • Use segmentation of one band to identify “vertices” in time series
  • Smooth between vertices in other bands
  • Result: “Pseudo-images” with year-to-year noise removed, but actual change retained

NBR

Brightness

Greenness

1985

1991

1995

2007

Wetness

Kennedy et al. LandTrendr

stable cross time classification
Stable cross-time classification
  • Stable spectral space allows application of consistent models, classification rules across time

1984

1986

1987

1988

1999

2002

2006

Kennedy et al. LandTrendr

stable cross time classification12

Partial

Canopy removal

Full

Stable cross-time classification
  • Stable spectral space allows application of consistent models, classification rules across time

1999

2002

2006

Area of detail

Loss of vegetative cover

Kennedy et al. LandTrendr

extension l7 gap filling cloud filling
Extension: L7 Gap-filling, cloud filling
  • Multiple images ingested per year
    • Best image (closest to median date) chosen if cloud-, gap-free
    • Otherwise use secondary images
  • Resultant image without gaps, clouds
    • Result of both standard mosaicking + fitting

Landsat 5

August 10,

2006

Landsat 7

September 4,

2006

Landsat 7

August 18,

2006

2006

Median

Date

Kennedy et al. LandTrendr

landtrendr timesync

LandTrendr & TimeSync

Opening of the archive = paradigm shift in Landsat change detection

Automated algorithms (LandTrendr - Kennedy, Vegetation Change Tracker – Huang) already exploiting the archive regionally, nationwide, as well as internationally (plus: exploring MSS-ETM+)

LandTrendr composites to remove clouds and SLC-off gaps

Smooths time series between change vertices enabling functional linkage between spectral properties and map classifications through time

Given temporal and spatial richness of change information from algorithms, paucity of independent data to conduct validation

TimeSync fills this void, and is backed up with more traditional reference data, where available.