Update the description of azimuth !

[fredericschmidt]

The description of the azimuth is not correct, not standard and not symmetric with the other definitions of azimuth angles in this STAC extension.

<< Viewing azimuth angle. The angle measured from the sub-satellite point (point on the ground below the platform) between the scene center and true north. Measured clockwise from north in degrees (0-360). >>

=> should be better phrased as:

<< View azimuth angle. From the scene center point on the ground, this is the angle between truth north and the sub-satellite point (point on the ground below the platform). Measured clockwise in degrees (0-360). >>

similar to

<< Sun azimuth angle. From the scene center point on the ground, this is the angle between truth north and the sun. Measured clockwise in degrees (0-360). >>

[jlaura]

Agreed that an update to the definition would be valuable. Here is an alternative as used by the ISIS planetary processing software:

A clockwise angle from a point of origin to a point of interest.

The azimuth is measured in a positive clockwise direction from a reference line. The reference line is formed by a line drawn horizontally from the origin point to the right side of the image (3 o'clock reference if the image is viewed as a clock face) Azimuth can also be referred to as Image Azimuth.

Note that this differs from a north azimuth:

A clockwise angle from a point of origin to true North.

The North Azimuth is measured in a positive clockwise direction from a reference line. The reference line is formed by a line drawn horizontally from the origin point (pixel location) to the right side of the image (3 o'clock axis). Refer to Azimuth.

[gadomski]

@jlaura would you mind making a PR to that effect?

[fredericschmidt]

Agreed that an update to the definition would be valuable. Here is an alternative as used by the ISIS planetary processing software:

Those ones are also interesting but image-frame based. Not that relevant for a non-nadir image.

By the way, I don't like at all the wording from ISIS: an angle is not a line but an angle bewteen two lines ! The reference to the line toward the North is missing here...

If you want, you may add that :

view:image_azimuth number North azimuth angle in the image frame. The angle measured in the middle of the image from the right side of the image (3 o'clock reference if the image) toward the North direction projected in the image frame. Measured clockwise from right side of the image toward the projected North in degrees (0-360).