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<p>Digital Earth Africa provides a range of <strong>continental-scale data products </strong>derived from satellite imagery and models. Each product is a coherent dataset representing a particular measurement or analysis, often compiled over time or across scenes. </p>
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<p><strong>1. Data Products and Services:</strong> DE Africa organises products into thematic services (e.g., Surface Water, Vegetation, Coastal, Agriculture). For example, the <strong>Water Observations from Space (WOfS)</strong> service includes water-mask products for individual scenes and aggregated summaries; the <strong>GeoMAD</strong> service produces cloud-free multispectral composites (geomedian and deviation layers) using Landsat or Sentinel data; the <strong>Coastlines</strong> service provides annual shoreline vectors and change hotspots. External datasets (e.g., Copernicus DEM, SRTM, WaPOR) are also available via DE Africa.</p>
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<p><strong>2. Product Structure:</strong> Each product consists of one or more <strong>bands (measurements)</strong> on a regular grid. For instance, the Sentinel-2 Annual GeoMAD product has 14 bands (reflectance plus MAD layers) at 10 m resolution, while a Landsat GeoMAD has 10 bands at 30 m. Products often share a common coordinate reference system (e.g., EPSG:6933) and use simple file formats. <strong>Cloud-Optimized GeoTIFF (COG)</strong> is the standard format for DE Africa products – this means each file is a GeoTIFF optimised for efficient cloud access and streaming. For example, the Cropland Extent (2019) map is a 10 m COG containing two bands (mask and prob), while the Fractional Cover (30 m) product contains three percentage bands (bs, pv, npv) for bare soil, green <em>vegetation, and non-green vegetation</em></p>
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<p dir="ltr" style="line-height: 1.7999999999999998; margin-top: 10pt; margin-bottom: 10pt;"><strong>3. Finding Metadata:</strong> DE Africa provides a <strong>Metadata Explorer</strong> at <a href="https://explorer.digitalearth.africa/products" target="_blank">explorer.digitalearth.africa </a>to browse products by time and location. In the Explorer, you select a product (e.g., “Landsat 8 SR”) and a date range, and a map shows blue tiles where data exists. The sidebar shows information about selected datasets (count, product name, CRS, etc.). For example, the screenshot below shows the Landsat-8 Surface Reflectance product (“ls8_sr”) over 2018, with a map and timeline of available scenes:</p>
<p dir="ltr" style="line-height: 1.7999999999999998; margin-top: 10pt; margin-bottom: 10pt;"><em><img height="751" width="875" src="/assets/courseware/v1/38203c61ca25ba573d4785798e634b8e/asset-v1:digitalearthafrica+DEA101+2021+type@asset+block/Image25.png" alt="screenshot below shows the Landsat-8 Surface Reflectance " /></em></p>
<p dir="ltr" style="line-height: 1.7999999999999998; margin-top: 10pt; margin-bottom: 10pt;"><em>DE Africa Metadata Explorer interface. You select (1) the product and year, then (2) the time filter. The map (3) shows where data is available (blue tiles). The sidebar (4) displays product metadata (name, number of scenes, CRS, etc.).</em></p>
<p dir="ltr" style="line-height: 1.7999999999999998; margin-top: 10pt; margin-bottom: 10pt;">This tool answers “<strong>Where and when</strong> does data exist?”. By contrast, the <strong>DE Africa Map</strong> at <a href="https://maps.digitalearth.africa/" target="_blank">maps.digitalearth.africa</a> is used to visualise the data itself. In other words, use the Map to see imagery and layers, and use the Explorer to find availability.</p>
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<p dir="ltr" style="line-height: 1.7999999999999998; margin-top: 10pt; margin-bottom: 10pt;">To ground these ideas, here are some key products (from continental services) and their essence:</p>
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<li><strong>Water Observations from Space (WOfS):</strong> A water-detection service using Landsat. It includes scene-level water masks (WOFL: Water Observation Feature Layers, one per image) and aggregated summaries (annual and all-time water frequency).</li>
<li><strong>GeoMAD (Geomedian & MAD):</strong> Cloud-free mosaics. GeoMAD produces multiband composites (e.g., Sentinel-2 or Landsat annual/seasonal medians) plus median absolute deviation layers. These composites let you see a clear view of the land surface for a given period.</li>
<li><strong>Coastlines Monitoring:</strong> Annual shoreline positions at 30 m resolution, plus rates of change and hotspot indicators as vectors. Useful for studying coastal erosion or growth over time.</li>
<li><strong>Vegetation Indices:</strong> Products like Fractional Cover (bands of vegetation fractions), NDVI Anomaly (monthly NDVI deviation), and NDVI Climatology (long-term baseline mean/std NDVI per month). These help quantify vegetation health and variability.</li>
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<p>These products (and others listed on the DE Africa Data & Products page) come with metadata that describes their structure (bands, resolution, data type) and coverage. You can view detailed specifications on the DE Africa documentation site or via the Metadata Explorer. DE Africa data are <strong>publicly available on AWS S3</strong>, organised in buckets by sensor and service, and indexed in a <strong>STAC catalog</strong> for programmatic access.</p>
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