Downloading¶

Quick download¶

For a single granule, download! fetches from the URL and stores locally:

using SpaceLiDAR, Extents

vietnam = Extent(X=(102.0, 107.0), Y=(8.0, 12.0))

g = search(:ICESat2, :ATL08; extent=vietnam)[1]
download!(g, "data/")
g.url  # now points to "data/ATL08_..."

Batch downloads with aria2c¶

When downloading multiple granules, SpaceLiDAR automatically uses aria2c for parallel, resumable downloads:

granules = search(:ICESat2, :ATL08; extent=vietnam)
download!(granules, "data/")

This writes a temporary URL list and calls aria2c -c (continue/resume). No manual setup needed — aria2c is bundled via Aria2_jll.

Credentials¶

NASA Earthdata requires authentication. Set up once:

SpaceLiDAR.netrc!("your_username", "your_password")

This writes to ~/.netrc (or ~/_netrc on Windows).

Exporting URL lists¶

If you prefer to download externally (e.g., with wget or a download manager):

granules = search(:ICESat2, :ATL08; extent=vietnam)
SpaceLiDAR.write_urls("urls.txt", granules)

Then use any tool:

aria2c -c -i urls.txt -d data/

Loading local granules¶

Once downloaded, load from disk:

# Single file — auto-detects mission and product from filename
g = granule("data/ATL08_20201121151145_08920913_006_01.h5")

# All .h5 files in a folder (recursive)
gs = granules("data/")

Files with .aria2 suffixes (incomplete downloads) are automatically skipped.

Syncing a folder¶

sync checks what you already have and downloads only new granules:

# Sync all products found in folder (downloads newer granules)
sync("data/")

# Sync a specific product
sync(:ATL08, "data/")

# Restrict sync to an extent
sync("data/"; extent=vietnam)

How it works:

Scans the folder for existing granules
Finds the latest date among them
Searches NASA CMR for granules after that date
Downloads only the new ones

To force a full re-check (not just newer):

sync("data/", true)  # all=true

Incremental update pattern¶

A common workflow for keeping a local mirror up to date:

using SpaceLiDAR, Extents

folder = "/data/icesat2/atl08/"
vietnam = Extent(X=(102.0, 107.0), Y=(8.0, 12.0))

# First time: search and download everything
granules = search(:ICESat2, :ATL08; extent=vietnam)
download!(granules, folder)

# Later: just sync — only fetches what's new
sync(folder; extent=vietnam)