Harmonized Landsat Sentinel

About Harmonized Landsat Sentinel Data

Data Information

Harmonized Landsat Sentinel is a NASA initiative to produce a Virtual Constellation of surface reflectance (SR) data from the Operational Land Imager (OLI) and Multi-Spectral Instrument (MSI) aboard the Landsat 8-9 and Sentinel-2 remote sensing satellites, respectively. The combined measurement enables global observations of the land every 2–3 days.

Input products are Landsat 8-9 Collection 2 Level 1 top-of-atmosphere reflectance and Sentinel-2 L1C top-of-atmosphere reflectance, which NASA radiometrically harmonizes to the maximum extent, resamples to common 30-meter resolution, and grids using the Sentinel-2 Military Grid Reference System (MGRS) UTM grid. Because of this, the products are different from Landsat 8-9 Collection 2 Level 2 surface reflectance and Sentinel-2 L2A surface reflectance. Learn more about the data here.

Basic Facts

Accessing 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 collection you are querying. This chapter will help you understand the parameters for HLS data. For an overview of all API parameters see the API Reference.

Endpoint Locations

Data type identifier: hls

Use hls as the value of the input.data.type parameter in your API requests. This is mandatory and will ensure you get HLS data.

Filtering Options

This chapter will explain the input.data.dataFilter object of the 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 NASA for easier distribution.

maxCloudCoverage

Sets the upper limit for cloud coverage in percent based on the precomputed cloud coverage estimate for each 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.

constellation

Selects constellation. By default, both constellations are selected. Note that for any type of data mosaicking, for requests containing bands which are present in only one constellation (e.g. RedEdge1), it is highly recommended (but not strictly necessary) to set the corresponding constellation parameter. Otherwise, your request may fail as the band is not guaranteed to be present for all data being mosaicked.

Processing Options

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

Available Bands and Data

Information in this chapter is useful when defining input object in evalscript. Any string listed in the column Name can be an element of the input.bands array in your evalscript.

[1]: dataMask has no source resolution as it is calculated for each output pixel.

For more info about the bands, check HLS user guide.

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. 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 optical data, the relation between DN and REFLECTANCE (default unit) is: DN = 10000 * REFLECTANCE.

For thermal data, the relation between DN and BRIGHTNESS_TEMPERATURE (default unit) is: DN = 100 * BRIGHTNESS_TEMPERATURE.

For angle view data, the relation between DN and DEGREES (default unit) is: DN = 100 * DEGREES.

[1]: Top of the Atmosphere Brightness Temperature.

Scenes Object

scenes object stores metadata. An example of metadata available in scenes object for HLS when mosaicking is ORBIT:

Properties of a scenes object can differ depending on the selected mosaicking and in which evalscript function the object is accessed. Working with metadata in evalscript user guide explains all details and provide examples.

Catalog API Capabilities

To access HLS 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.

Collection identifier: hls

Filter extension

• eo:cloud_cover cloud cover percentage
• constellation (possible values)

Distinct extension

• date

Examples

HLS examples