if I scan a map and post it on the web then I violated some law somewhere but what if I take a picture of my sister holding the map and the map is still useable as a map and post it?
Probably a violation. If the map is readable, the judge will likely rule that the copyright holder’s permission is necessary.
A lot depends on context, though.
The same laws apply. You would still be posting the map in a way that would allow for it’s use without someone having to purchase one themselves. There are ways around copyright laws that would allow you to post most, but not all of the map. The easiest way is to use the map as editorial content. Post part of the map along with an “editorial” about the map. I have used this method for other items and have never been bothered by anyone.
Except for USGS maps, which IIRC are not copyright.
No Government maps/charts are copywrited. Though is is bad form to use a base map and not cite it. I think that the US is the only country to have no copywrites on gov. info. I know that at least Canada and the UK both do.