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L1 Basic (L1B)

drawing

Product description

The L1 Basic (aka L1B and QuickView) product is a 4-band (RGB and Near infrared) product characterised by its low processing time and that can be generated from Mark IV and Mark V satellites raw imagery. It is geolocated and projected to the ground but not orthorectified and it is presented at native resolution. This implies that different captures may have different pixel sizes depending on the altitude and the off-nadir angle of the satellite at capture time. This imagery product is currently used in Rapid Response products, as well as the base collection to browse the archive.

Technical characteristics

Parameter

Mark IV

Mark V
Spectral bands

Blue : 450 - 510 nm
Green: 510 - 580 nm
Red : 590 - 690 nm
NIR : 750 - 900 nm

Blue : 450 - 517 nm
Green: 517 - 583 nm
Red : 597 - 690 nm
NIR : 759 - 890 nm

GSD

0.7m - 1.35m 1

 0.73m - 0.81 1

Scene Swath

4.8 - 5.5 Km 1

 6.8Km - 8.5Km 1

Image bit depth

8-bit for VISUAL, 16 bit for TOA

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Max Off-Nadir angle

± 25 deg

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Algorithms applied

Radiometric correction, Band Aligment, Geolocation, Projection to UTM

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Geolocation Accuracy

<= 30m TBC CE90 2

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Band aligment

<= 2px TBC

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Image format

GeoTiff, LZW loseless compression

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Ancilliary files

Cloud and usable data mask (GeoTiff), preview (PNG) and thumbnail (PNG).

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Product presentation

L1 Basic has two subproducts: the VISUAL and the TOA. The VISUAL version of the product is an 8-bit GeoTIFF and has a streched histogram that visually enhances the image for exploration purposes. The TOA (Top-of-atmosphere) version refers to a radiometrically corrected, 16-bit GeoTIFF in reflectance units (included in the metadata there are coeficcients to convert reflectance into radiance).

drawing The L1 Basic product can be consumed in two packaging options: as a full scene, or as tiles. On the one hand, a scene is a single image as it was captured by one of the satellites of our fleet. On the other hand, tiles are a more granular version of the same scene, that can be used for more localized exploration and consumption.

Users can obtain L1 Basic products in two different ways: by requesting a new capture, that is, submitting a tasking order through the Tasking API and by purchasing archive data in the catalog. Currently, L1 Basic products are delivered to a pre-configured AWS S3 bucket but in the future it will be possible to download them directly from the Tasking API. Explore available L1B tiles using our Archive STAC API, under the quickview-visual and quickview-toa collections.

Projection

This imagery product is projected in the Universal Transverse Mercator (UTM) coordinate reference system. Note: if a scene is captured across different UTM zones, the entire scene/all tiles are projected to the zone with more data. The specific EPSG code (of the UTM zone) is indicated in the proj:epsg property (for tiles) or in the metadata files (for scenes).

Product components

Each L1 Basic imagery product, in both tiles and scene presentations have multiple elements associated with them as well as the corresponding metadata.

Raster, preview and thumbnail

drawing drawing drawing

The full resolution raster as well as downsampled versions for preview and thumbnails.





Cloud and usable data mask

drawing The mask is a single band GeoTIFF. Each pixel value correspond to a different semantic class as follows:

  • 0: nodata
  • 1: valid_data
  • 128: shadow_data
  • 255: cloud

Metadata

Metadata is available for the entire scene in STAC and ISO format, and per tile in STAC format. Common metadata can be found across tiles of the same capture. In tiles, the metadata corresponds to the information of that tile. For scenes, some metadata is aggregated.

The following table shows the description of each field and an example corresponding to the capture used in previous section.

Field Description Example
gsd The ground sampling distance of the image, in meters. 0.78
datetime Capture date and time of the tile. In UTC. 2023-09-22T02:29:17.823169536+00:00
platform Satellite name that acquired the imagery. newsat13
grid:code Satellogic 2km grid code for this tile. See below. SATL-2KM-52N_137_2088
proj:epsg The EPSG code of the projection (corresponds to a UTM zone). See below. 32652
eo:cloud_cover The percentage of cloud cover found on the image, from 0 to 100. 41.7
view:off_nadir The off-nadir angle for the capture measured in degrees. 25.8465
view:sun_elevation The elevation angle of the sun at the target at the moment of the capture, in degrees. 50.4441
view:sun_azimuth The azimuth angle of the sun at the target the with respect to the north, in degrees. 156.912
view:incidence_angle The incidence angle is the angle between the vertical (normal) to the intercepting surface and the line of sight back to the satellite at the scene center, in degrees (0-90). 43.4
view:azimuth Viewing azimuth angle. The angle measured from the sub-satellite point (point on the ground below the platform) between the scene center and true north. Measured clockwise from north, in degrees (0-360). 1.212
satl:outcome_id A unique identifier of the associated capture with this tile. d5627157-d1aa-472d-9daa-a55086fd32c2--161551
satl:ground_lock Indicates if there was enough GCP on the ground to geolocate the image. A false value indicates that the location of the image was done with onboard telemetry from the satellite and not a basemap. True
satl:valid_pixel The percentage of valid pixels on the tile. If less than 100 it means that part of the image contains no data values. 81.533
satl:shadow_cover The percentage of shadows, probably due to clouds found on the image, from 0 to 100 [experimental use]. 4.9
satl:product_name The unique name of the product of which this tile corresponds to. QUICKVIEW_VISUAL
satl:product_version The version of the product. Uses semantic versioning. 1.7.1
satl:ba_[BAND]_response The FFT phase correlation response between the [BAND] band and the [BAND] from the basemap. [BAND] can be Red, Green, Blue. NIR is not evaluated, since that band is usually not present in most basemaps. Typically a number >0.5 means there is good correlation between the basemap and the image being measured. For tiles with a value lower than that, the remaining geoaccuracy measuremnents are not relevant. 0.785
satl:ba_[BAND]_radial Radial error between the [BAND] band and the Green band, in pixels. 0.057
satl:ba_[BAND]_xshift X direction error between the [BAND] band and the Green band, in pixels. [BAND] can be Red, Blue, NIR. -0.004
satl:ba_[BAND]_yshift Y direction error between the [BAND] band and the Green band, in pixels. [BAND] can be Red, Blue, NIR. -0.057
satl:geoaccuracy_[BAND]_radial Radial error for the [BAND] band with respect to the basemap, in meters. [BAND] can be Red, Green, Blue, NIR. 9.289
satl:geoaccuracy_[BAND]_xshift X direction error between the [BAND] band with respect to the basemap, in meters. [BAND] can be Red, Green, Blue, NIR. 8.13
satl:geoaccuracy_[BAND]_yshift Y direction error between the [BAND] band with respect to the basemap, in meters. [BAND] can be Red, Green, Blue, NIR. 4.495
satl:geoaccuracy_[BAND]_response The FFT phase correlation response between the Green band and the [BAND]. [BAND] can be Red, Green, Blue, NIR. Typically a number >0.5 means there is good correlation between the basemap and the image being measured. For tiles with a value lower than that, the remaining geoaccuracy measuremnents are not relevant. 0.764
satl:uint16_to_reflectance_[BAND] The scale to apply to the DN value of every pixel to obtain reflecantes units between 0 and 1 . [BAND] can be Red, Green, Blue, NIR. Only available for TOA versions of the product. It has a fixed value. 0.0001
satl:uint16_to_radiance_[BAND] The scale to apply to the DN value of every pixel to obtain radiance units of W/(m² sr nm) . [BAND] can be Red, Green, Blue, NIR. Only available for TOA versions of the product. 0.0005934402

Packaging specification

All the components of the product are included and/or mapped into the two different packacing options, as tiles or as scenes following their corresponding support format.

Tiles

drawing The QuickView tiles are available on the Archive STAC API. Each STAC item is a 2km by 2km square tile. They are aligned to a fixed discrete grid, aligned to the prime meridian of each UTM zone (coordinate 500000m). Each tile has a designated grid code included in the property grid:code as follows:

SATL-<GRID SIZE>-<UTM ZONE> _ <X> _ <Y>

Where X and Y correspond to the easting and northing coordinates of the bottom left corner of the tile.

For example the grid:code SATL-2KM-10N_298_2062 should be interpreted as: - SATL grid of 2km by 2km - On UTM zone 10N - With the left bottom corner at 298,000m easting and 2062,000m northing.

Each item/tile contains the following assets/components:

STAC Item asset name Component
analytic The full resolution raster corresponding to the tile.
preview A 128x128 pixels PNG preview of the raster.
thumbnail A 64 x 64 pixels PNG thubmnail of the raster.
cloud The GeoTIFF cloud mask as defined above.

Scenes

Scenes are delivered as a single folder. The folder name follows the following format: <DATE>_<TIME>_SN<SATELLITE_NUMBER>_<PRODUCT_NAME>_<PAYLOAD>_<TARGET_ID> (for example 20231114_222725_SN22_L1B_MS_23322). It contains both the VISUAL and TOA versions of the product.

The content of a typical scene is detailed as follows: 

.
<DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_<TARGET_ID>
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_footprint.kml
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_metadata_iso.xml
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_metadata_stac.geojson
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_preview.png
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_thumbnail.png
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_toa_factors.geojson
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_CLOUD.vrt
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_TOA.vrt
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_TOA.vrt.ovr
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_VISUAL.vrt
├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_VISUAL.vrt.ovr
└── rasters
    ├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_CLOUD_<N>.tif
    ├── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_TOA_<N>.tif    
    └── <DATE>_<TIME>_SN<SATELLITE_NUMBER>_L1B_MS_VISUAL_<N>.tif

File Description
*.vrt A GDAL Virtual raster that contains all the corresponding TIFFs in the rasters folder. In case of very big images, mutliple TIFFS can be included in the package. CLOUD, VISUAL and TOA are the files available.
*.vrt.ovr Overviews of the VRT. They are small and only a few scales are added so as not to impact negatively on the total size.
*_footprint.kml The overall raster ground footprint in KML.
*_metadata_iso.xml A text-based document in ISO 19115-2 format containing the key information from the metadata of the product. See the metadata section for more information.
*_metadata_stac.geojson A text-based document in STAC format containing the aggregated information of the product. See the metadata section for more information.
*_preview.png A lower resolution image representation of the entire scene.
*_thumbnail.png An even lower resolution thumbnail of the entire scene.
*_toa_factors.geojson A GeoJSON file that contains the coefficients to convert reflectance units to radiance units and digital numbers (DN). Small variation of the radiance coefficients can be expected between tiles of the same scene.
rasters/*_<N>.tif The full resolution raster that comprises the full scene. For very large captures, the rasters are divided into smaller chunks. The number <N> is the chunk number.

TOA_factors

The image on the right depicts a *_toa_factors.geojson file overlaid with the scene as a reference. The polygons in the GeoJSON file correspond to the scene tiles.

Changelog

[v1.7.1] 2024-09-06

  • Compatibility with L1A v1.0.0 ICD.

[v1.7.0] 2024-06-04

  • Using L1A version 1.0.0.

[v1.6.0] 2024-05-21

  • Added STAC properties on azimuth, ona, incidence_angle, sun azimuth and elevation on the view extension.

[v1.5.0] 2024-04-22

  • Bugfixing and stability improvements.

[v1.4.0] 2024-04-12

  • Bugfixing and stability improvements.

[v1.3.0] 2024-03-28

  • Fix small tilings right-bottom.
  • Fix on PSF deconvolution weights.

[v1.2.0] 2024-02-29

  • Improved ratio of locked ground images.
  • TOA conversion factors (uint16_to_radiance) metadata is now corrected.
  • From this version, the Off-nadir is computed from satellite POV instead of observation POV (the elevation angle).
  • Fixed extra_samples metadata removing warnings when opening files.

[v1.1.10] 2023-11-27

  • TOA thumnails fixed.
  • Less brightness image on Visual product.

[v1.1.9] 2023-11-16

  • MarkV Orirentations should be fixed.

[v1.1.8] 2023-11-16

  • Geolocation improvements.
  • Over-water band alignment improved.

[v1.1.7] 2023-11-13

  • Bug fixes.
  • Ability to start from L1A products.

[v1.1.6] 2023-11-03

  • Internal improvements, no change in imagery product.

[v1.1.5] 2023-11-03

  • Band alignment improvements on saturated areas.

[v1.1.4] 2023-10-31

  • Internal improvements, no change in imagery product.

[v1.1.3] 2023-10-27

  • Improved thumbnail quality.

[v1.1.2] 2023-10-25

  • Fixed counterclockwise exterior ring in metadata footprint [Warning: breaking change!].
  • Improved saturation mask for cloud detector.

[v1.1.1] 2023-10-24

  • Improved imagery sharpness.
  • Fixed tile ID to reflect the real position of the tile.

[v1.1.0] 2023-10-19

  • Improved visual product for consistency among very long captures.
  • Tiling size to 2km.
  • Changed production naming from RR to QUICKVIEW.
  • Previews encoded in png now include alpha channel.

[v1.0.0] 2023-09-18

  • Initial release.

  1. Varies with altitude of the satellite and off nadir angle. ↩↩↩↩

  2. Varies with terrain and only applicable for terrains with rich features. See the "satl:ground_lock" parameters for more information. ↩

Last update: 2024-12-02