LCMAP CONUS Science Products are released in Collections, with new collections including non-provisionary versions of the previous collection’s final (provisionary) year as well as provisional products for the most recent product year.
LCMAP CONUS Collection 1.0, which covered 1985-2017, was released in Summer 2020. This was replaced by Collection 1.1 (1985-2019) in Spring 2021, followed by Collection 1.2 (1985-2020) in Fall 2021, and Collection 1.3 (1985-2021) in Summer 2022.
Each Collection contains 10 science products for the years covered, based on the implementation of the LCMAP Continuous Change Detection and Classification (CCDC) algorithm. The final product year (2020 for Collection 1.2, 2021 for Collection 1.3, etc.) is considered provisional. Collections also contain updates to other product years resulting from additional Landsat Analysis Ready Data (ARD) for the most recent years and refitting of end models in the previous collection.
LCMAP Collection Updates:
- The input Landsat ARD observations are consistent with LCMAP Collection 1.0 input over the corresponding time period (1982 thru the end of 2017), except for the four tiles listed under the caveats and constraints section on the Collection 1.2 page.
- The change detection algorithm (PYCCD) was updated to constrain statistical calculations. This limited forward processing by only applying the algorithm to observations occurring after the most recent break in the previous collection (LCMAP Collection 1.3 CCDC ADD Section 2.5.6).
- The supervised learning classification model developed for Collection 1.0 was used to classify the land cover in subsequent collections (LCMAP Collection 1.3 CCDC ADD Section 3.5.4).
What is contained in an LCMAP Collection?
Subsequent LCMAP Collections contain the same 10 data products as Collection 1.0. Collections are based on Landsat ARD through the most recent product year. This results in annual products for the years 1985 to the most recent year, including non-provisional products for the previous collection’s final year, and provisional products for the most recent year.
Are there any data format changes?
There are no data format changes between the collections.
Why an entire new collection? Why can’t I simply add the new years to the previous products I already downloaded?
By extending the temporal sequence of data, previous change detection harmonics and land cover classifications may be impacted. How far back changes may be seen is dependent on the last spectral break for any given pixel location. Data prior to the last spectral break for a pixel location does not change between the two datasets, except for the four tiles listed under the caveats and constraints section on the Collection 1.2 page.
See sections 2.5.6 and 3.5.4 from the LCMAP CCDC Collection 1.3 ADD and section 4.1.1 from the LCMAP Collection 1.3 Science Product Guide for further discussion.
Can products/years from different collections be used interchangeably?
We recommend that users use the latest data, as additional information helps overcome errors in previously released collections.
What changes can users expect to see?
Users can expect to see updated land cover information, as additional years of observations add more information for the harmonic model fits, especially after the last model break recorded in the previous collection. The additional observations can cause a land cover class to be different than what was predicted in the previous collection.