Getting ICEsat and ICESat-2 data

http://openaltimetry.org/ for data from ICESat and ICESat-2. You can get CSV or HDF5 (which you would have to convert to GIS format on your own, say in Matlab)
- Select Browse for the satellite you want
- The quick start tutorial might be helpful
Navigate the map to desired area. Track points will appear as you zoom in, and in the upper left, you will see the percentage of the points that show on screen. This number increases as you zoom in. Becasue the orbits shift with its cycle, you will actually get data somewhere between the track and its two neighbors.

ICESat-2

Product information in the upper right describes the types of data. You probably want ATL08: ATLAS/ICESat-2 L3A Land and Vegetation Height.
Select a region, using the button on the upper left
Click on the track you want.
Pick the date from those available
Insure that the points on the desired profile appear; it is easy to leave them with the past profile
Click in the region, on the highlighted orbit, and click on one of the dates which should trigger the display of some of the points, and then view ATL08 elevation profile from the popup menu.
- You want to use the section of the form with the red rectangles on the screen capture to the left.
- Insure that you have gotten a new track. The program tends to retain the same track, especially if you did not pick the track with the date option. The track number will be on the title for the graph. The track will also be in the files names, after the date
- Insure you are downloading the Elevation Profile (ATL08), and not the ATL06 (Land Ice Surface) or ATL12 (Ocean Surface) or the ATL13 (inland waters). If you get these, you will have to do a lot of manipulation with the data to make it workable. Which of the products appear depends on the location. The Red X's shows where you do not want to download data if you are looking for elevations on land.
- The track will not be in the download file names, but is inside the CSV data.
- If there are multiple dates, you can switch among them on the top of the form.
- The 3D viewer option below can be useful
- All 6 beams will be in the same download file; you can Filter to only display one beam; if you zoom in, you will see the separate ground tracks. This will show the ground and the top of the canopy, and uncertainty estimates.
You can also view the ATL02 photons (which leads to much larger data sets)
- Pick the tab above the graph to switch between photons and elevations
- Each beam will be a separate download. The beam name will be in the xml metadata file.
- There is a confidence value, 0-4, for Noise, Buffer, Low, Medium, High
- The 3D viewer option below can be useful, but may be slow with the volume of data to display
- Icesat-2 photon data to LAS which will transfrom to geoid, and can merge multiple input files
Data volumes can be large, and consider the area needed carefully. Excel might choke on some of the files, but MICRODEM should be able to use them.
Heights will be on WGS84 ellipsoid.
Prep the data

ICESat

Click select a region button on the upper left of the left.
Draw a box
Pick Download data as a CSV file
All data in the box will be downloaded. You can Filter on the TRACK or CAMPAIGN. If you combine these two fields into a single string field, you can get profiles
There will be a single elevation at each point
Data volume will be small, so you can pick fairly large areas.
There is no metdata, just the CSV
Elevations are referenced to Topex/Poseidon/Jason ellipsoid, which is close to the WGS84 ellipsoid ftp://sidads.colorado.edu/pub/DATASETS/icesat/tools/idl/ellipsoid/README_ellipsoid.txt
Prep the data

Prep the ICESat-2 data

Download data as CSV, unzip with decompress option in MICRODEM (File, Tools menu) which will allow selection of multiple files, and puts them in the same directory and not subdirectories.
With an open map, import the CSV files. This process can be slow, but in future operations you should open the DBF file and not the CSV file.
- You can merge multiple CSV files into one DBF on the Database menu. You can Filter this by date, track, or beam.
  - The makes some operations easier if you want to look at a large area and are not concerned about the dates the data was collected.
  - It makes it harder to look at the different dates (you have to filter), but there is an automatic filter for the most important graph.
  - This will automatically doe the ICESat-2 file cleanup
- Open database (shapefile) in MICRODEM which can keep each track in its own databaase
From the DB: Stats Menu, Point clouds to analysze global DEMs, ICESat-2 file cleanup if you did not already do it.
- Gets the geoid, and makes geoid heights for the ground and canopy top from then the geoid offset from the WGS84 ellipsoid.
- Extracts the date from the FILE_NAME field
- Limits the excessive decimals for some of the fields
- This process can be slow
If you want to analyze by time
- Edit, Date/TIME, Split date field (YYYYMMDD)
- Edit, Date/TIME, Time fields to dec years
If you want to look at landcover
- Open the land cover to match your map area. Copernicus 100 m data will be the best choice unless you want to go back farther in time
- Edit, DEM, Add nearest integer elevation from DEM: required for things like landcover when you want to filter the DB by category
- You can then Filter uisng the landcover category number
- If you want to track landcover change over time
  - Open each of the data sets.\
  - Subset & zoom one map to get just the area you want
  - File, Match other maps, This coverage area
  - On each map, Right click on map, Popup Legends
  - Report, Export HTML, Single table. In addition to opening in a browser, the table will be on the clipboard and you can paste it into Excel.
  - In Excel you can combine the various years.

Last revision 2/5/2023