Docs: Add GNSS Master

Author: nseidle

docs/gis_software_android.md

@@ -114,6 +114,74 @@ Now you can begin using the SparkFun RTK device with Field Genius.
 
 [GNSS Master](https://play.google.com/store/apps/details?id=com.gnssmaster&hl=en_US) is a great utility when a given GIS app does not have an NTRIP Client. GNSS Master connects to a RTK device over Bluetooth (or Bluetooth BLE) as well as any correction source (NTRIP, PointPerfect, even USB Serial), and then acts as the phone's location using Mock Location.
 
+**Note:** Most GIS apps will not need GNSS Master or Mock Location enabled and this section can be skipped.
+
+Read how to [Enable Mock Location](connecting_bluetooth.md/#enable-mock-location).
+
+![GNSS Master main menu](<img/GNSSMaster/SparkFun RTK GNSS Master - Main.png>)
+
+From the GNSS Master main screen, select *GNSS Receiver Connection*.
+
+![GNSS Receiver Selection](<img/GNSSMaster/SparkFun RTK GNSS Master - Receiver Selection.png>)
+
+Pick the RTK device to connect to from the list, then click *Connect*. The **Data Rate** should increase indicating data flowing from the RTK device to the GNSS Master app. Click the back button to return to the main screen.
+
+![Correction Input](<img/GNSSMaster/SparkFun RTK GNSS Master - Correction Input.png>)
+
+Select **Correction Input** to setup an NTRIP Client.
+
+![Corrections List](<img/GNSSMaster/SparkFun RTK GNSS Master - Correction Source List.png>)
+
+This is one of the powerful features of GNSS Master - multiple connections can be entered. This is helpful if you switch between locations or NTRIP Casters and your GIS software only allows entry of a single NTRIP source. GNSS Master supports corrections from NTRIP Casters but also PointPerfect and a direct serial connection to a GNSS receiver. This can be really helpful in advanced setups.
+
+![NTRIP Client information](<img/GNSSMaster/SparkFun RTK GNSS Master - NTRIP Client Input.png>)
+
+Enter your NTRIP Caster information then click **SAVE**.
+
+![Data from Caster](<img/GNSSMaster/SparkFun RTK GNSS Master - Correction Source Data Flowing.png>)
+
+Once connected the **Data Rate** should increase above 0 bytes per second.  Return to the home screen by hitting the back button.
+
+![Enable Mock Location](<img/GNSSMaster/SparkFun RTK GNSS Master - Mock Location.png>)
+
+Enable mock location. If GNSS Master throws an error, re-enable GNSS Master as your [Mock Location provider](connecting_bluetooth.md/#enable-mock-location) in Developer Options.
+
+Once enabled, any GIS app that selects 'Internal' or 'Phone Location' as its source will instead be fed the high precision NMEA being generated by the RTK device connected over Bluetooth.
+
+## Lefebure 
+
+[Lefebure NTRIP Client](https://play.google.com/store/apps/details?id=com.lefebure.ntripclient&hl=en_US) is the original app for getting correction from an NTRIP caster and down over Bluetooth. 
+
+**Note:** Most GIS apps will not need Lefebure or Mock Location enabled and this section can be skipped.
+
+The problem is that if Lefebure is connected to the RTK device providing RTCM corrections over Bluetooth, then other GIS applications cannot use the same Bluetooth connection at the same time. That's where mock locations save the day. Lefebure can be setup to take over or 'mock' the GPS location being reported by the phone. Nearly all GIS apps can use the phone's GPS location. So if the phone's location is magically super precise, then Lefebure can be the NTRIP Client and data provide, and your GIS app is none the wiser, and uses the phone's location.
+
+Read how to [Enable Mock Location](connecting_bluetooth.md/#enable-mock-location).
+
+![LEfebure settings](<img/Lefebure/SparkFun RTK Lefebure - Main.png>)
+
+Once mock locations are enabled, click on the *Settings* gear in the top left corner.
+
+![NTRIP Settings](<img/Lefebure/SparkFun RTK Lefebure - NTRIP Settings.png>)
+
+If needed, an NTRIP Client can be setup to provide corrections over Bluetooth to the RTK device.
+
+![NTRIP Client Settings](<img/Lefebure/SparkFun RTK Lefebure - NTRIP Client Settings.png>)
+
+Enter the Caster information and hit the back button.
+
+![Receive Settings](<img/Lefebure/SparkFun RTK Lefebure - Receiver Settings.png>)
+
+Select *Receiver Settings*.
+
+![Bluetooth and Mock location enable](<img/Lefebure/SparkFun RTK Lefebure - Receiver Settings Bluetooth.png>)
+
+Select the RTK device that has been paired over Bluetooth. Also enable Mock Locations. Hit the back button to return to the main screen.
+
+![alt text](<img/Lefebure/SparkFun RTK Lefebure - Getting Data with Mock Location.png>)
+
+Press the **Connect** button. The app will connect to the NTRIP Caster. Now, any GIS app that selects 'Internal' or 'Phone Location' as its source will instead be fed the high precision NMEA being generated by the RTK device connected over Bluetooth.
+
 ## QField
 
 ![Opening page of QField](img/QField/SparkFun%20RTK%20QField%20-%20Open%20Project.png)