DOC/grdgradient.rst: Update URL link to "Hill-Shading and the Reflectance Map" by Horn (1981)

yvonnefroehlich commented 2 months ago

Description of proposed changes

This PR is a suggestion to update the URL link to the publication "Hill-Shading and the Reflectance Map" by Horn (1981) from http://people.csail.mit.edu/bkph/papers/Hill-Shading.pdf (which seem not freely available anymore 🙁) to the ResearchGate upload at https://www.researchgate.net/publication/2996084_Hill_shading_and_the_reflectance_map. There people can download a full text, but the PDF file provided at http://dx.doi.org/10.1109/PROC.1981.11918 is not freely available (I can only download it via my KIT university account).

Fixes #8582

Reminders

[ ] Make sure that your code follows our style. Use the other functions/files as a basis.
[ ] Add tests for new features or tests that would have caught the bug that you're fixing.
[ ] Describe changes to function behavior and arguments in a comment below the function declaration.
[ ] If adding new functionality, add a detailed description to the documentation and/or an example.

joa-quim commented 2 months ago

Don't know why it fails. That paper is still in place and accessible. When I click on that link it works.

yvonnefroehlich commented 2 months ago

Don't know why it fails. That paper is still in place and accessible. When I click on that link it works.

Interesting. For me I get this message:

Forbidden You don't have permission to access this resource.

yvonnefroehlich commented 2 months ago

But OK, if this link works for all.

Maybe also somebody else @Esteban82 or @seisman can test this (: .

GenericMappingTools / gmt