Show the ArcticDEM change detection layer(s)

[robyngit]

This issue is to track the requirements for & progress made on displaying Dr. Chunli Dai's pan-Arctic elevation differencing products from the ArcticDEM

Data qualities & workflow requirements

• The data comprises 2km x 2km GeoTiff tiles that cover the Arctic

• GeoTiffs are 221x221 pixels, 1 band per GeoTiff, CRS EPSG:3413

• Shapefiles for all tiles available upon request

• There are six layers available (see plots below), not all will be visualized. Here is an example of the data available for each tile:

  • 41_16_1_1_01_01_listused.txt: a list of ArcticDEM strip file names used for change estimation.
  • 41_16_1_1_01_01_jump.tif: elevation change in meters.
  • 41_16_1_1_01_01_jumpstd.tif: elevation change uncertainty in meters.
  • 41_16_1_1_01_01_eventtimeT1.tif: date of the closest measurement before detected change. The date format is YYYYMMDD
  • 41_16_1_1_01_01_eventtimeT2.tif: date of the closest measurement after change.
  • 41_16_1_1_01_01_nov.tif: The number of overlapping DEMs used for each pixel.
  • 41_16_1_1_01_01_bitmask.tif: Integer flag of whether the estimated change has high confidence level. 1 is good, and 0 is bad.

• The most important layer to show (likely the first one we will visualize) is the elevation change in meters.

• The tiles overlap somewhat, and we should display data from just one of the tiles in the areas of overlap (rather than taking some aggregate of pixels at the same location)

• The best way to determine which tile is preferred in areas of overlap is to read in data from another set of 2km x 2km tiles: for example, we could use the "number of overlapping DEMs" tiles to determine which of the overlapping tiles has the most DEMs overall.

• The workflow will involve deduplicating areas of overlap, as described above, in addition to essentially re-tiling the data to correspond with an OGC Two Dimensional Tile Matrix Set.

• There will be edge effects at the intersection of the 2km x 2km tiles just because of the way the tiles were produced, we may not be able to resolve these artifacts during the workflow

41_16_1_1_01_01_jump.tif

41_16_1_1_01_01_eventtimeT1.tif & 41_16_1_1_01_01_eventtimeT2.tif

41_16_1_1_01_01_nov.tif

Other features that would aid in visualizing this data

• A timeline to show the elevation change at each point in time
• The ability to click a point and see a plot of the change in elevation over time for that pixel
• The ability to show different versions of the same layer (e.g. the same data fit with different functions)

Related articles

• Quantifying mass flows at Mt. Cleveland, Alaska between 2001 and 2020 using satellite photogrammetry
• Detection and Assessment of a Large and Potentially Tsunamigenic Periglacial Landslide in Barry Arm, Alaska
• Project summary

[robyngit]

Chunli suggested that when we resample the data (to create tiles at different resolutions), we should take the median