As part of ongoing upgrades to its in-house mapping service, Apple on Friday added a handful of entries to its rolling list of providers that supply the company with maps data, business listings and satellite imagery.

In an update to Apple's acknowledgments webpage for Maps data partners, the company quietly announced new business listings provider partnerships with E-WEGO, NavAds, Yellow Pages Group Corp. and Yellow Pages Turkey.

Today's update officially recognizes local search integration of user-generated reviews from TripAdvisor and Booking.com, two major sources of travel-related information. AppleInsider first reported on the additions in February.

After a rocky debut in 2012, Apple Maps has greatly improved as new data providers and internal Apple teams work to refine data accuracy, Flyover imagery, point-of-interest databases and more.

With an overhaul thought to be in the works, Apple this month acquired high-precision GPS hardware and software maker Coherent Navigation. It is not yet known how the firm's technology will be assimilated into Apple's products.

Most recently, Dutch-based mapping data service TomTom confirmed earlier this week that it renewed a contract to provide Apple with street-level data covering North America and Europe.