I agree.
However, if you go for a purely "academic" approach of map making, Artes Liberales (Astrology) would be tremendously useful to mimic Ptolemaic work - at least to measure and record coordinates. Let's face it, "real cartography" requires a lot of calculation and math, and the appropriate skill covering that is Artes Liberales. It also requires you mage to travel on said location. Alternatively, he can send somebody skilled in Astrology do some coordinate recording on his behalf.
Building a compass and other magical tools describes in Celestial magic could be useful too - altough not to make horoscope 
To draw the map, you could go with Profession: Scribe, or even Painting.
With your troop approval, Profession: Mapmaker or Cartographer could include both the drawing skill and some rudimentary mathematical skills to estimate distance. Up to your troop approval if it goes as far as including the ability to use stars navigation and Ptolemaic coordinate.
Having Area knowledge cannot harm (possibly more for small scale map, to include interesting local details like rumored infernal caves, haunted forest and whatnot).
A Virtue like Inventive Genius would be nice way to explain your modern (and unique) approach to mapmaking. If you combine that with Free Expression, Faerie courts might be looking for you to draw their ideal home or scene to set a story.
That's for the non-magical approach.
The magical approach might not require much mundane skill depending on how heavily your mage will rely on its magic.
Intellego (Terram, Aquam or even Herbam for Mountains, Rivers & Lakes, Forest) spells with Boundaries limit can give you a pretty accurate shape of what you are mapping - if your magus is an indoor guy, he might send grogs to collect Arcane connections. You will have a map maker who never set a foot out of his lab!
Intellego Imaginem will allow you to scout large area (again all depends on the spell level & range). Re(In)Im allows you to travel to places and perceive like if you were personnaly there - having it invested in a magical item to maintain concentration will definitely help.
Intellego Animalem will allow you to see the world from a bird (other animals seems less useful for this purpose) - if it is your familiar, you don't need to control him, otherwise a ReAn will do the trick.
Just be mindful on not spying on another Covenant/magus as there could be a case for magical scrying charges.
And to draw the map itself, you can go through various ways like CrIm with Animal/Herbam requisit to create a map from your memories (Animal and Herbam requisit are for the support and the inks) - it will be a ritual for permanent map. ReAq (An/He) to control inks flowing on a blank support (canvas, paper...). Of course, in both case we are talking about Craft magic which requires good Finesse skills.
More cumbersome but more impressive map can be done in 3D by carving wood, shaping clay or sculpting stone. It has the advantage to use only one forms, and paiting can be done quickly afterwards.
Unless you use magic to scout area (and are not limited by the number of time you can cast the spell), you will need good memory. There, the art of Memory can definitely help you.