Assuming you can read, Bob doesn't need to make a video. Look at the top left corner of each page of his pdf. There is a symbol like a V. The left arm is vertical, indicating True North (Grid North, or map North, if you will). The other arm points to the right, and is marked "26deg E". That indicates to chart users that the local declination of Magnetic North is 26 deg right of True North.
Every single map and chart intended for the purposes of navigation has the local declination marked on it, either as the V-simbol on the Invercargill Airfield Chart, or often as a compass rose on nautical charts. Airfield charts have a short lifespan and are frequently replaced, but navigational maps are expected to be in use for several years so normally include, not only the declination at publication, but the expected annual progression.
In the case of Invercargill, for instance, if you flew a heading of North on your aircraft compass, without applying this adjustment, you would actually be flying North-North-East. Perhaps more importantly, if you flew at low altitude compass-West after departing Invercargill you might expect to be over the sea, but you would actually be flying NNW, into a mountain range.
Its not just for aircraft; its the same for ships, and every boy-scout map-reader knows it.