Digital Earth Africa GeoMAD: Cloud-Free Satellite Composites for Africa

Digital Earth Africa provides annual and six-month cloud-free satellite composites for the entire African continent. The service combines Landsat data dating back to 1984 and higher-frequency Sentinel-2 data, processed using geomedian and Median Absolute Deviation statistics. Data is available under a Creative Commons Attribution 4.0 license.

Use Cases

• Generate true-color images for visual inspection of anthropogenic or natural landmarks based on the geomedian composite.
• Develop complex land classification algorithms based on the full spectral dataset.
• Analyze seasonal variation and change over time using the six-month semiannual datasets and Median Absolute Deviation layers.
• Compare long-term environmental trends using the Landsat archive dating back to 1984.

Strengths

• Provides cloud-free composites by discarding invalid data and mathematically summarizing observations over time.
• Offers both annual and six-month semiannual timeframes to capture different environmental dynamics.
• Leverages two sensor archives: Landsat for historical analysis back to 1984 and Sentinel-2 for higher frequency and resolution.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• Row count and file size are unknown, which may limit suitability assessment.

Provenance

Source

Digital Earth Africa

Collection Method

Satellite data from Landsat and Sentinel-2 sensors compiled over specific timeframes and processed using geomedian and Median Absolute Deviation statistics.

Time Range

Landsat archive dates back to 1984; specific composite timeframes are annual and six-month.

Freshness

Last update date is unknown; freshness unverified.

Geography

Covers the entire African continent.