Update altm:nominal_track field to include recommended value for non-representative item geometry

Author: emmanuelmathot

README.md

@@ -30,7 +30,7 @@ The fields in the table below can be used in these parts of STAC documents:
 | altm:instrument_type | string                                                                                              | Primary instrument type. See the list of [primary instrument types](#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](https://datatracker.ietf.org/doc/html/rfc7946#section-3.1.4) | An array of coordinates used to define the nominal track on the earths surface. This track is essentially a line that is representative of the product but does not include points for every value. This value is recommended ONLY if the item geometry is not representative of the track. |
+| altm:nominal_track   | [GeoJSON LineString Coordinates Array](https://datatracker.ietf.org/doc/html/rfc7946#section-3.1.4) | 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](https://github.com/stac-extensions/sentinel-3/blob/main/deprecated.md)