Currently Apple iOS 8.3 no longer works with external Bluetooth GPS receivers. It seems that on April, Apple Location Services in latest version iOS 8.3 doesn't transmit the GPS data received from these GPS GNS2000 to the application for navigation.
Apple Inc.. is aware of this bug iOS and promises a solution as soon as possible. I hope that this problem will be solved in the next few days.
Several manufacturers applications for navigation have warned before update iOS 8.3 as BadElf, see : http://bad-elf.com/blogs/bad-elf/18013536-alert-compatibility-issue-with-apple-ios-8-3-and-external-gps-receivers
Hope for users impacted an iOS version 8.3.1 will come quickly fix this bug. Can be expected because an update must quickly fix another bug much more important for Apple : the troubleshoooting of the Touch ID on many devices.