Gridded Coverage Extension 16-bit PNG - Signed / Unsigned contradiction?

[jerstlouis]

In section 6.2. Storage formats and grid cell values ( http://docs.opengeospatial.org/is/17-066r1/17-066r1.html#_storage_formats_and_grid_cell_values ) it says:

using PNG (16-bit, signed integer)

Requirement 13 says:

the data SHALL be 16-bit unsigned integer (single channel - "greyscale").

As far as I understand PNG only supports unsigned integers. From https://en.wikipedia.org/wiki/Portable_Network_Graphics :

The permitted formats encode each number as an unsigned integer value using a fixed number of bits

It seems a proper fix would be to keep the requirement as-is but fix 6.2, but what are implementations currently doing?

Am I missing something?

[jyutzler]

We concur that a change is needed. We just need a pull request. Assigning to @ryanfranz.

[ryanfranz]

Pull request from https://github.com/ryanfranz/geopackage-tiled-gridded-coverage created.
This can be added to a corrigendum

[ryanfranz]

@jyutzler Changes have been merged, this can be closed

[jyutzler]

Closed via #575