This post will cover equirectangular projection using the Pannellum toolset.  Details about Pannellum can be found here, https://pannellum.org/documentation/overview/.  I have included two types of images as examples, cube and spherical.  Both of them give a spatial sense to the observer viewing out from inside a box or ball.

The example patterns represent a rudimentary reticle for measurement that can be applied to a physical environment.