Altimetry Extension Specification

• Title: Altimetry
• Identifier: https://stac-extensions.github.io/altimetry/v0.1.0/schema.json
• Field Name Prefix: altm
• Scope: Item
• Extension Maturity Classification: Proposal
• Owner: @emmanuelmathot

This document explains the Altimetry Extension to the SpatioTemporal Asset Catalog (STAC) specification.

• Examples:
  • Sentinel-3 example: Shows the basic usage of the extension in a STAC Item with Sentinel-3 data.
• JSON Schema
• Changelog

Fields

The fields in the table below can be used in these parts of STAC documents:

• Catalogs
• Collections
• Item Properties (incl. Summaries in Collections)
• Assets (for both Collections and Items, incl. Item Asset Definitions in Collections)
• Links

Field Name	Type	Description
altm:instrument_type	string	Primary instrument type. See the list of primary instrument types.
altm:instrument_mode	string	Instrument mode.
altm:sampling_rate	number	Sampling rate of the instrument in Hz.
altm:nominal_track	GeoJSON LineString Coordinates Array	An array of coordinates used to define the nominal track on the earths surface. This value is recommended ONLY if the item geometry is not representative of the acquisition track.

Note

Various fields and objects in this extensions replace deprecated fields from the sentinel-3 extension. Please see the section sentinel-3 mapping for more information.

Primary Instrument Types

The following values are valid for the altm:instrument_type field:

Value	Description
sar	Synthetic Aperture Radar
doppler	Doppler
laser	Laser
microwave	Microwave Radiometer
other

Sentinel-3 Mapping

The following table shows the mapping between the deprecated fields in the Sentinel-3 extension and the fields in the Altimetry extension.

Sentinel-3 Field Name	Altimetry Field Name	Altimetry Field Value
s3:lrm_mode	altm:instrument_mode	lrm
s3:sar_mode	altm:instrument_mode	sar

Contributing

All contributions are subject to the STAC Specification Code of Conduct. For contributions, please follow the STAC specification contributing guide Instructions for running tests are copied here for convenience.

Running tests

The same checks that run as checks on PR's are part of the repository and can be run locally to verify that changes are valid. To run tests locally, you'll need npm, which is a standard part of any node.js installation.

First you'll need to install everything with npm once. Just navigate to the root of this repository and on your command line run:

npm install

Then to check markdown formatting and test the examples against the JSON schema, you can run:

npm test

This will spit out the same texts that you see online, and you can then go and fix your markdown or examples.

If the tests reveal formatting problems with the examples, you can fix them with:

npm run format-examples