RegExp to extrct longitude and latitude from a string

I inherited a database with a location field that contains data in the following style:

a:3:{s:7:"address";s:32:"Belgrade, Serbia";s:3:"lat";s:10:"44.8234945";s:3:"lng";s:17:"20.46218669999996";}
a:3:{s:7:"address";s:30:"Los Angeles, CA, United States";s:3:"lat";s:10:"34.0522342";s:3:"lng";s:12:"-118.2436849";}
a:3:{s:7:"address";s:58:"Wauwatosa, United States";s:3:"lat";d:43.05008220000001;s:3:"lng";d:-87.9901927;}
a:3:{s:7:"address";s:32:"London, England";s:3:"lat";d:51.4743113;s:3:"lng";d:-0.1010046;}

The data in the field varies, but what is constant in all of them is the last part of the string: "lat";d:51.4743113;s:3:"lng";d:-0.1010046;}
I would like to clean them up and extract only the lat and lng from the string from the above and echo them like:

Coordinates: 51.4743113,-0.1010046

Any help is appreciated, many thanks!