When referencing a map from Google maps, your reference list entry should include a retrieval date as the details of the map are likely to change. Use (n.d.). as these maps are 'dynamically generated' and don't have a specific publication date.
Author. (n.d.). [Description of map]. Retrieval date and URL
Google. (n.d.). [Google map of Wintec City Campus Hamilton]. Retrieved November 22, 2018, from
https://www.google.com/maps/place/Wintec+City+Campus/@-37.7888704,175.276469,17z/data=!3m1!4b1!4m5!3m4!1s0x6d6d18a57fa16281:0x72b05e2e8812d179!8m2!3d-37.7888704!4d175.2786577
Examples
Reference list entry
Google. (n.d.). [Google map of Wintec City Campus Hamilton]. Retrieved November 22, 2018, from
https://www.google.com/maps/place/Wintec+City+Campus/@-37.7888704,175.276469,17z/data=!3m1!4b1!4m5!3m4!1s0x6d6d18a57fa16281:0x72b05e2e8812d179!8m2!3d-37.7888704!4d175.2786577
In-text citations
Narrative
As this map from Google (n.d) shows...
Parenthetical
... (Google, n.d.).