Sentinel-2 L2A

About Sentinel-2 L2A Data

Mission Information

Dedicated to supplying data for Copernicus services, Sentinel-2 is carrying a range of technologies, such as multi-spectral imaging instruments for land, ocean and atmospheric monitoring. It's is delivering high-resolution optical images for land monitoring, emergency response and security services. The satellite's multispectral imager provides a versatile set of 13 spectral bands spanning from the visible and near infrared to the shortwave infrared.

More information:

• https://sentinel.esa.int/web/sentinel/missions/sentinel-2
• Dataset user guide

Basic Facts

Attribution and Use

EU law grants free access to Copernicus Sentinel Data and Service Information for the purpose of the following use in so far as it is lawful: a) reproduction; b) distribution; c) communication to the public; d) adaptation, modification and combination with other data and information; e) any combination of points a to d.

See more details on the use of Copernicus Sentinel data and service information

Tracing based on Sentinel imagery is allowed for commercial purposes as well.

Acknowledgment or credit: Contains modified Copernicus Sentinel data [Year] processed by Sentinel Hub

Accessing Sentinel-2 L2A Data

To access data you need to send a POST request to our process API. The requested data will be returned as the response to your request. Each POST request can be tailored to get you exactly the data you require. To do this requires setting various parameters which depend on the datasource you are querying. This chapter will help you understand the parameters for S2L2A data. To see examples of such requests go here, and for an overview of all API parameters see the API Reference.

Endpoint Locations

Data type identifier: sentinel-2-l2a

Use sentinel-2-l2a (previously S2L2A) as the value of the input.data.type parameter in your API requests. This is mandatory and will ensure you get Sentinel-2 L2A data.

Filtering Options

This chapter will explain the input.data.dataFilter object of the S2L2A process API.

mosaickingOrder

Sets the order of overlapping tiles from which the output result is mosaicked. Note that tiles will in most cases come from the same orbit/acquisition. The tiling is done by ESA for easier distribution.

maxCloudCoverage

Sets the upper limit for cloud coverage in percent based on the precomputed cloud coverage estimate for each Sentinel-2 tile as present in the tile metadata. Satellite data will therefore not be retrieved for tiles with a higher cloud coverage estimate. For example, by setting the value to 20, only tiles with at most 20% cloud coverage will be used. Note that this parameter is set per tile and might not be directly applicable to the chosen area of interest.

previewMode

Sentinel Hub API is optimised for full resolution data access as this is what most users need. While the Sentinel-2 L1C has low-resolution previews generated, this is not yet the case for Sentinel-2 L2A. Lower resolution processing is enabled by default, but the performance degrades after going beyond 250m per pixel (up to 1500m per pixel).

Processing Options

This chapter will explain the input.data.processing object of the S2L2A process API.

A visual representation of upsampling results using various algorithms is available here.

Available Bands and Data

This chapter will explain the bands and data which can be set in the evalscript input object. Any string listed in the column Name can be an element of the input.bands array in your evalscript.

*dataMask has no source resolution as it is calculated for each output pixel.

Note: The cirrus band B10 is excluded as it does not contain any "bottom of the atmosphere" information (Source: Sen2Cor Configuration and User Manual).

Units

The data values for each band in your custom script are presented in the units as specified here. In case more than one unit is available for a given band, you may optionally set the value of input.units in your evalscript setup function to one of the values in the Sentinel Hub Units column. Doing so will present data in that unit. The Sentinel Hub units parameter combines the physical quantity and corresponding units of measurement values. As such, some names more closely resemble physical quantities, others resemble units of measurement.

The Source Format specifies how and with what precision the digital numbers (DN) from which the unit is derived are encoded. Bands requested in DN units contain exactly the pixel values of the source data (See also Harmonize Values). Note that resampling may produce interpolated values. DN is also used whenever a band is derived computationally (like dataMask); such bands can be identified by having DN units and N/A source format. DN values are typically not offered if they do not simply represent any physical quantity, in particular, when DN values require source-specific (i.e. non-global) conversion to physical quantities.

Values in non-DN units are computed from the source (DN) values with at least float32 precision. Note that the conversion might be nonlinear, therefore the full value range and quantization step size of such a band can be hard to predict. Band values in evalscripts always behave as floating point numbers, regardless of the actual precision.

The Typical Range indicates what values are common for a given band and unit, however outliers can be expected.

For Sentinel-2 optical data, the relation between DN and REFLECTANCE (default unit) is: DN = 10000 * REFLECTANCE. See also Harmonize Values.

*Higher values are expected in infrared bands. Reflectance values can easily be above 1.
** AOT = DN / 1000.

Harmonize Values

ESA updated the Sentinel-2 processing baseline to version 04.00 in January, 2022, which introduced breaking changes to the interpretation of digital numbers (DN). The optional harmonizeValues parameter gives you extra control over the values which enter your evalscript.

harmonizeValues can be true (default) or false, and it's behavior depends on the units chosen:

• REFLECTANCE:
  • harmonizeValues = true: negative reflectance values are clamped to zero. In other words, pixels with negative reflectance return zero reflectance instead.
  • harmonizeValues = false: negative reflectance values can be returned.
• DN:
  • harmonizeValues = true: DN values are harmonized so they are comparable with data from previous baselines. Therefore it still holds that DN = 10000 * REFLECTANCE. In addition, negative values are clamped to zero.
  • harmonizeValues = false: DN values are exactly as provided in the source files themselves. The "true" DN value, you could say. Don't forget that values have different definitions with different processing baselines, careful with mosaicking!

Mosaicking

All mosaicking types are supported.

Scenes Object

scenes object stores metadata, for an example see scenes object for Sentinel-2 L1C.

Collection Specific Constraints

• Each Sentinel-2 satellite takes 100.6 minutes for an entire orbit, with S2A and S2B orbiting 180 degree apart. By setting a time interval to less than 50 minutes, there should be no overlap possible between different acquisitions, even near the poles.
• For atmospheric correction, ESA's official Sen2Cor is used. In most cases the processing is done by ESA itself. On users' request we can also process some archive data using the same processor.

Catalog API Capabilities

To access Sentinel 2 L2A product metadata you need to send search request to our Catalog API. The requested metadata will be returned as JSON formatted response to your request. This chapter will help with understanding Sentinel 2 L2A specific parameters for search request.

Collection identifier: sentinel-2-l2a

Filter extension

• eo:cloud_cover cloud cover percentage

Distinct extension

• date

Examples

S2L2A examples