Next, you want your readers to be able to find the maps you're referring to. Use the "share or embed" option on the maps page to generate a permalink.
Lastly, what should the reference look like? APA provides some guidance at http://blog.apastyle.org/apastyle/2015/08/how-to-cite-online-maps.html
For one example they show
Google. (n.d.). [Google Maps directions for driving from Ingolstadt,
Germany, to Geneva, Switzerland]. Retrieved August 4, 2015, from [url
I would change the author as specified in Google's attribution guidelines above, and I would replace "driving directions for ...." to "Area Calculator" or some such.
After doing this, I'd let the editorial process take over, having done your due diligence.