Using an external GPS with iCMTGIS II on iPad

“For high precision GPS positioning I did connect an external GPS receiver to the iPad via Bluetooth. How and where can I select the GPS receiver in the application? Does it switch automatically between the internal GPS receiver and the external connected via Bluetooth? Where can I see in the application which GPS is connected and how can I decide which one to use and fix as default GPS receiver?”

The iOS devices can only work with GPS receivers approved by Apple. Using an external GPS receiver often improves position accuracy. Assuming the external GPS is an iSXBlue II, a Dual XGPS-150, a Garmin Glo or a Bad Elf GPS receiver, it will provide NMEA data to iOS. The Location Service will distribute the location data to the apps. Currently, all of our apps get the GPS data from the Location Service of the iOS device.

So, to use the external GPS, make sure you have turned on Location Services under Privacy. Also, on the Location Services page, find iCMTGIS II and turn the switch on to make Location Service available for this app. (Do this for the app you are using, such as iGPSGIS II, Utility Data Collection, Stakeout iCMT, Farming GPS GIS, Forester GPS GIS, etc.)

For iOS devices with built-in GPS, how would one know which GPS is being used?

The short answer is: Your iOS device will serve the GPS data from the external GPS when the internal GPS is not actively being used.

Not to leave you in the fog, here is the long answer:

1. To make use of GPS, Location Service must be turned on under Settings and also turned on for the specific app you are using.

2. The iOS device will automatically use the internal GPS if you turn on GPS within an app while no external GPS is connected.

3. When any app is using the internal GPS, iOS cannot work with an external GPS connected to the device.

4. Therefore, to make use of the connected external GPS, you will want to turn off GPS from all running GPS apps (including the one you are actively using) then turn on GPS within the app you are actively using.

5. It will also help to turn on Airplane mode then turn on Bluetooth and make sure Location Service is active for the app.

6. When Bluetooth connection is lost, then iOS uses the internal GPS. This could happen randomly.

Usually, the first time you turn on GPS in the app, the device will connect with the external GPS. So to make sure the device is connected with the external GPS, turn off GPS (from the menu bar of the app such as iCMTGIS II) then turn it on again. Or, reconnect the Bluetooth GPS. The status maybe shown as “Connected”, but just tap on it to make it reconnect again.


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