Build an android and iOS app

Hello, I am looking for someone who can build a gps-based app if that's the word for it. It is basically an application only related to my workplace and new employees have hard time locating places. So the application will have a map of my workplace and layers containing specific layouts on the map which the user can turn on and off to display certain buildings and locations and the user can navigate through the app which means the gps should give the exact location etc. I will provide the actual map of the workplace, google map coordinates so when you use the app it knows your location and also multiple overlays on the map which can be turned off and on. And finally users need to register and be approved by me before using the app. if you need more info please contact me.