Multidimensional data cubes from analysis-ready data (ARD) of CBERS-4, CBERS-4A, Landsat-8 and Sentinel-2 satellite images
Data cubes are generated from ARD products from the BDC data collections. In the context of the BDC project, three grids with cells of different sizes were defined to contain the products according to the spatial resolution of the ARD images. Grids have sizes of 1×1.5, 2×3 and 4×6 degrees and a cartographic projection is associated with them. Figure 1 depicts these grids.
Data cubes can be categorized into two types: identity and time composite. Identity cube represents acquisitions of images on the original sensor dates, while in a composite cube a pixel value is chosen into a period of time, for example 16 days or 1 month, to compose the final product.
The temporal composition function calculates or selects the value of a pixel within a time interval on an identity cube. The temporal composition function can be mean, median or STACK. For example, given a time interval the average time composition evaluates all free cloud and cloud shadow values given a cloud mask and then calculates the final average value for each spectral band. In the case of STACK, a sorting is made based on the useful area of the images, considering the cloud cover and shadow, so the resulting value of the STACK composition is obtained from the first value found, if there is cloud or shadow in the first ordered image, the values of the pixels are taken from the second image and so on. Figure 2 illustrates these procedures.
BDC products are stored and distributed in COG (Cloud Optimized GeoTIFF) format, the table below illustrates the data cubes generated in the BDC project.
Data cubes generated by the BDC.
| Cube Collection | Satellite | Sensors | Spatial Resolution (m) | Temporal Compositing |
|---|---|---|---|---|
| CB4_64 | CBERS-4 | AWFI | 64 | Identity |
| CB4_64_16D_STK | CBERS-4 | AWFI | 64 | 16 days Stack |
| CB4_20_1M_STK | CBERS-4 | MUX | 20 | 1 month Stack |
| LC8_30 | Landsat-8 | OLI | 30 | Identity |
| LC8_30_16D_STK | Landsat-8 | OLI | 30 | 16 days Stack |
| MOD13Q1 | TERRA | MODIS | 250 | 16 days Best Pixel |
| MYD13Q1 | AQUA | MODIS | 250 | 16 days Best Pixel |
| S2_10 | Sentinel 2A/2B | MSI | 10 | Identity |
| S2-SEN2COR_10_16D | Sentinel 2A/2B | MSI | 10 | 16 days Stack |