Product Package

Pixxel imagery is delivered as an L2A product package: orthorectified, atmospherically corrected Bottom-of-Atmosphere (BOA) reflectance.

The valid range is given in physical units, i.e. after the scale factor has been applied.

The image raster is stored as unsigned 16-bit integers (UInt16). To convert a stored DN to the physical quantity, apply:

physical value = DN × Scale + Offset

For example, a pixel value of 12 500 corresponds to a BOA reflectance of 12 500 × 0.00002 = 0.25. A pixel value of 0 is reserved for no data.

Filename

Every file in a product package follows a structured naming convention, illustrated above. This makes each file traceable to its source image. A typical image raster is named:

FF01_20011230_00501045_0000021756_XL0.tif

The filename has five underscore-separated segments:

1. Satellite ID (4 characters): the source satellite platform, e.g. FF01 (see Satellite Details).
2. Acquisition date (8 digits): the image acquisition date in YYYYMMDD format (UTC).
3. Product descriptor (8 digits): three fields concatenated together:
   • the spatial resolution in metres, zero-padded to 3 digits (e.g. 005 for 5 m);
   • a 2-digit product iteration number, reserved for reprocessed versions of the same image (currently always 01);
   • the number of spectral bands, zero-padded to 3 digits (e.g. 045).
4. Image ID (10 digits): the unique image identifier, zero-padded.
5. Product identifier (3 characters): the content of the file (see the table below).

The image raster, its ENVI header and its XML metadata file all use the XL0 identifier and differ only in their extension (_XL0.tif, _XL0.tif.hdr and _XL0.xml). All other files replace XL0 with their own identifier, e.g. _PCL.tif or _FPT.geojson.

Package Contents

The table below lists the files in the product package. Here <stem> is the product filename without its extension, e.g. FF01_20011230_00501045_0000021756_XL0.

The product package therefore contains six files.

Image Raster

The image raster (<stem>.tif) is the primary dataset of the package. It holds one band per spectral channel, ordered by band identifier and projected in the UTM coordinate system on the WGS-84 datum. The file is a band-interleaved, LZW-compressed BigTIFF, tiled in 512 × 512 pixel blocks.

The scale factor, offset and unit listed above are stored in the GeoTIFF band metadata. GDAL-based software such as QGIS can therefore convert the stored values to physical units automatically. Each band is described as <BandID>_WV_<wavelength>nm (the central wavelength is rounded to 0.1 nm) and carries the following band-level tags:

• BAND_NAME: the band identifier;
• WAVELENGTH: the central wavelength in nm;
• BANDWIDTH: the FWHM in nm;
• SOLAR_IRRADIANCE: the band-averaged solar irradiance in W·m⁻²·µm⁻¹;
• VALID_RANGE: the valid range in physical units;
• BAND_TYPE: Reflectance.

The red, green and blue bands listed in the RGB_Bands metadata field are tagged with the corresponding colour interpretation, so GIS software renders a natural-colour composite by default. The raster also carries dataset-level tags that repeat the key acquisition parameters of the XML metadata file: satellite, sensor, acquisition time, image ID, altitude, off-nadir angle, scene centre, solar angles, Earth-Sun distance, spatial resolution, creation time and copyright.

Metadata Files

Each package includes two metadata files that describe the image raster:

1. An XML metadata file (<stem>.xml). It records the acquisition parameters, processing level, geometric configuration, radiometric characteristics, processing versions and package contents. Its fields are described in Product Metadata.
2. An ENVI header file (<stem>.tif.hdr), which makes the GeoTIFF directly readable in ENVI-based workflows. The header sets file type = TIFF. It describes the raster dimensions, data type, band names, central wavelengths, FWHM, solar irradiance, scale factor, acquisition time, solar angles and map information. It also sets data ignore value = 0.

Product Classification Layer

The Product Classification Layer (PCL) (..._PCL.tif) is a single-band UInt16 GeoTIFF on the same grid as the image raster. Each pixel carries bit flags for land, water, cloud, cloud edge and snow/ice, which support downstream filtering and masking. Its encoding is described in Product Classification Layer.

Footprint

The footprint file (..._FPT.geojson) is a GeoJSON FeatureCollection in EPSG:4326. It holds the polygon that bounds the valid image pixels and enables quick visualisation of the spatial coverage in GIS applications. The footprint is also used to compute the Captured_Area metadata field.

True Colour Image

A JPEG preview (..._TCI.jpeg) is provided inside the product package for inspection of the scene.

The true colour rendering uses the first available band from each of the following sets: B057–B059 for red, B025–B027 for green and B004–B006 for blue. Each channel is linearly stretched over the valid pixels, from μ − 2.5σ (clipped at 0) to μ + 2σ, where μ and σ are the channel mean and standard deviation. A pixel is set to black (0) wherever any of the three source bands has no data. The rendering is for visual inspection only and should not be used for quantitative analysis.