Earlier this year I went on a long holiday to Japan and China. I have an Android phone and am a very big fan of OpenStreetMap. So I used OsmAnd (which uses OpenStreetMap data) to navigate through those countries. I made a spreadsheet with LibreOffice, which included a few links to certain location which are hard to find or do not have an address. Then I exported that .ods to a .pdf and was able to click on the links, which then openend perfectly in OsmAnd.
The URL I was able to use in my PDF document was this one (of course you can substitute longitude and latitude):
And then I helped a friend of mine with something similar to use on a website. Of course the link above did not work. After a short look on Wikipedia I found the page about Geo URI scheme. Constructing a URL with the Geo URI scheme will trigger the default navigation application on a mobile device to open the location. And of course, here you can also substitute the longitude and latitude.