Ingest satellite imagery in Azure Data Manager for Agriculture

Satellite imagery is a foundational pillar of agriculture data. To support scalable ingestion of geometry-clipped imagery, Microsoft partnered with Sentinel Hub by Sinergise to provide a seamless bring your own license (BYOL) experience for Azure Data Manager for Agriculture. You can use this BYOL experience to manage your own costs. This capability helps you with storing your field-clipped historical and up-to-date imagery in the linked context of the relevant fields.

Prerequisites

• To search for and ingest imagery, you need a user account that has suitable subscription entitlement with Sentinel Hub.
• Read the Sinergise Sentinel Hub terms of service and privacy policy.
• Have your providerClientId and providerClientSecret values ready.

Ingesting geometry-clipped imagery

Using satellite data in Azure Data Manager for Agriculture involves the following steps:

Consumption visibility and logging

Because all ingested data is under a BYOL model, the cost of a job is transparent. Azure Data Manager for Agriculture offers built-in logging to provide transparency on processing unit (PU) consumption for calls to upstream partner Sentinel Hub. The information appears under the SatelliteLogs category of the standard Azure Data Manager logging.

STAC search for available imagery

Azure Data Manager for Agriculture supports the industry-standard SpatioTemporal Asset Catalogs (STAC) search interface to find metadata on imagery in the Sentinel Hub collection before committing to downloading pixels. To do so, the search endpoint accepts a location in the form of a point, polygon, or multipolygon, plus a start and end date/time. Alternatively, if you already have the unique item ID, you can provide it as an array of up to five to retrieve those specific items directly.

Single-tile source control

Published tiles overlap space on the earth to ensure full spatial coverage. If the queried geometry lies in a space where more than one tile matches for a reasonable time frame, the provider automatically mosaics the returned image with selected pixels from the range of candidate tiles. The provider produces the best resulting image.

In some cases, using more than one tile isn't desirable and traceability to a single tile source is preferred. To support this strict source control, Azure Data Manager for Agriculture supports specifying a single item ID in the ingest job.

Reprojection

Azure Data Manager for Agriculture uses WGS84 (EPSG: 4326), a flat coordinate system. Sentinel-2 imagery is presented in UTM, a ground projection system that approximates the round earth.

Translating between a flat image and a round earth involves an approximation translation. The accuracy of this translation is set to equal at the equator (10 m^2) and increases in error margin as the point in question moves away from the equator to the poles.

For consistency, Azure Data Manager for Agriculture uses the following formula at 10 m^2 base for all Sentinel-2 calls:

$$ Latitude = \frac{10 m}{111320} $$

$$ Longitude = \frac{10 m}{\frac{111320}{cos(lat)}} $$

$$ \ Where\ lat = The\ centroid's\ latitude\ from\ the\ provided\ geometry $$

Caching

Azure Data Manager for Agriculture optimizes performance and costing of highly repeated calls to the same item. It caches recent STAC items retrieved by item ID for five days in the customer's instance and enables local retrieval.

For the first call to the search endpoint, Azure Data Manager for Agriculture brokers the request and triggers a request to the upstream provider to retrieve the matching or intersecting data items. The request incurs any provider fees.

Any subsequent search first directs to the cache for a match. If there's a match, data is served from the cache directly. This process doesn't result in a call to the upstream provider, so it doesn't incur more provider fees. If there's no match, or if the five-day retention period elapses, a subsequent call for the data is passed to the upstream provider. That call is treated as another first call, so the results are cached.

If an ingestion job is for an identical geometry, referenced by the same resource ID, and with overlapping time to an already retrieved scene, Azure Data Manager for Agriculture uses the locally stored image. The image isn't downloaded again from the upstream provider. There's no expiration for this pixel-level caching.

Satellite sources that Azure Data Manager for Agriculture supports

While Azure Data Manager for Agriculture is in preview, it supports ingesting data from the Sentinel-2 constellation.

Sentinel-2

Sentinel-2 is a satellite constellation that the European Space Agency (ESA) launched under the Copernicus mission. This constellation has a pair of satellites and carries a multispectral instrument (MSI) payload that samples 13 spectral bands: four bands at 10 m, six bands at 20 m, and three bands at 60-m spatial resolution.

Sentinel-2 has two products:

• Level 1 data for the top of the atmosphere.
• Level 2 data for the bottom of the atmosphere. This variant is atmospherically corrected.

Azure Data Manager for Agriculture supports ingesting and retrieving Sentinel_2_L2A and Sentinel_2_L1C data from Sentinel 2.

Image names and resolutions

APIs that you use to ingest and read satellite data (for Sentinel-2) in Azure Data Manager for Agriculture support the following image names and resolutions:

Points to note

Azure Data Manager for Agriculture uses CRS EPSG: 4326 for Sentinel-2 data. The resolutions quoted in the APIs are at the equator.

For the preview:

• A maximum of five satellite jobs can run concurrently, per tenant.
• A satellite job can ingest data for a maximum of one year in a single API call.
• Only TIFs are supported.
• Only 10-m, 20-m, and 60-m images are supported.

Next steps

• Test the Azure Data Manager for Agriculture REST APIs