iOS
Torch: 
There are a variety of 3rd party apps available for GIS and surveying for Android, iOS, and Windows. We will cover a few examples below that should give you an idea of how to get the incoming NMEA data into the software of your choice.
The software options for Apple iOS are much more limited because Apple products do not support Bluetooth SPP. That's ok! The SparkFun RTK products support additional connection options including TCP and Bluetooth Low Energy (BLE).
ArcGIS Survey123
ArcGIS Survey123 Home Screen
ArcGIS Survey123 is a popular offering from Esri that works well with SparkFun RTK products.
ArcGIS Survey123 connects to the RTK device over TCP. In other words, the RTK device needs to be connected to the same WiFi network as the device running ArcGIS. Generally, this is an iPhone or iPad.
Adding WiFi network to settings
The RTK device must use WiFi to connect to the data collector. Using a cellular hotspot or cellphone is recommended. In the above image, the device will attempt to connect to iPhone (a cell phone hotspot) when WiFi is needed.
TCP Server Enabled on port 2948
Next, the RTK device must be configured as a TCP Server. The default port of 2948 works well. See TCP/UDP Menu for more information.
RTK device showing IP address
Once the RTK device connects to the WiFi hotspot, its IP address can be found in the System Menu. This is the number that needs to be entered into ArcGIS Survey123. You can now proceed to the ArcGIS Survey123 app to set up the software connection.
ArcGIS Survey123 Home Screen
From the home screen, click on the 'hamburger' icon in the upper right corner.
ArcGIS Survey123 Settings Menu
From the settings menu, click on the Settings gear.
ArcGIS Survey123 Settings List
From the settings list, click on Location.
ArcGIS Survey123 List of Location Providers
Click on the Add location provider.
ArcGIS Survey123 Network Connection Type
Select Network.
ArcGIS Survey123 TCP Connection Information
Enter the IP address previously found along with the TCP port. Once complete, click Add.
ArcGIS Survey123 Sensor Settings
You may enter various sensor-specific settings including antenna height, if desired. To view real-time sensor information, click on the satellite icon in the upper right corner.
ArcGIS Survey123 Sensor Data
The SparkFun RTK device's data should now be seen. Click on the Map icon to return to the mapping interface.
ArcGIS Survey123 Map Interface
Returning to the map view, we can now begin gathering point information with millimeter accuracy.
QField
QField is a free iOS app that runs QGIS.
Modified NMEA messages on RTK Torch
First, configure the RTK device to output only the following NMEA messages:
- GPGGA
- GPGSA
- GPGST
- GPGSV
QField currently does not correctly parse other messages such as GPRMC, or RTCM. These messages will prevent communication if they are enabled.
These NMEA message settings can be found under the Messages menu, using the web config page or the serial config interface.
Adding WiFi network to settings
Next, the RTK device must use WiFi to connect to the data collector. Using a cellular hotspot or cellphone is recommended. In the above image, the device will attempt to connect to iPhone (a cell phone hotspot) when WiFi is needed.
TCP Server Enabled on port 9000
Next, the RTK device must be configured as a TCP Server. QField uses a default port of 9000 so that is what we recommend using. See TCP/UDP Menu for more information.
RTK device showing IP address
Once the RTK device connects to the WiFi hotspot, its IP address can be found in the System Menu. This is the number that needs to be entered into QField. You can now proceed to the QField app to set up the software connection.
QField Opening Screen
Click on QFieldCloud projects to open your project that was previously created on the QField Cloud or skip this step by using one of the default projects (Bee Farming, Wastewater, etc).
QField Main Map
From the main map, click on the 'hamburger' icon in the upper left corner.
QField Settings Gear
Click on the gear to open settings.
Click on the Settings menu.
QField Positioning Menu
From the Positioning menu, click Add.
QField Entering TCP Information
Select TCP as the connection type. Enter the IP address of the RTK device and the port number. Finally, hit the small check box in the upper left corner (shown in pink above) to close the window.
Once this information is entered, QField will automatically attempt to connect to that IP and port.
QField TCP Connected
Above, we see the port is successfully connected. Exit out of all menus.
QField Connected via TCP with RTK Fix
Returning to the map view, we see an RTK Fix with 11mm positional accuracy.
SW Maps
SWMaps is available for iOS here.
Make sure your RTK device is switched on and operating in Rover mode.
Make sure Bluetooth is enabled on your iOS device Settings.
The RTK device will not appear in the OTHER DEVICES list. That is OK.
iOS Settings Bluetooth
Open SWMaps.
Open or continue a Project if desired.
SWMaps will show your approximate location based on your iOS device's location.
iOS SWMaps Initial Location
Press the 'SWMaps' icon at the top left of the screen to open the menu.
iOS SWMaps Menu
Select Bluetooth GNSS.
iOS SWMaps Bluetooth Connection
Set the Instrument Model to Generic NMEA (Bluetooth LE).
iOS SWMaps Instrument Model
Press 'Scan' and your RTK device should appear.
iOS SWMaps Bluetooth Scan
Select (tick) the RTK device and press 'Connect'.
iOS SWMaps Bluetooth Connected
Close the menu and your RTK location will be displayed on the map.
You can now use the other features of SWMaps, including the built-in NTRIP Client.
Re-open the menu and select 'NTRIP Client'.
Enter the details for your NTRIP Caster - as shown in the SWMaps section above.
iOS SWMaps NTRIP Client
Click 'Connect'
At this point, you should see a Bluetooth Pairing Request. Select 'Pair' to pair your RTK with your iOS device.
iOS Bluetooth Pairing
SWMaps will now receive NTRIP correction data from the caster and push it to your RTK over Bluetooth BLE.
From the SWMaps menu, open 'GNSS Status' to see your position, fix type and accuracy.
iOS SWMaps GNSS Status
If you return to the iOS Bluetooth Settings, you will see that your iOS and RTK devices are now paired.
iOS Settings Bluetooth - Paired
Other GIS Packages
Hopefully, these examples give you an idea of how to connect the RTK product line to most any GIS software. If there is other GIS software that you'd like to see configuration information about, please open an issue on the RTK Firmware repo and we'll add it.
What's an NTRIP Caster?
In a nutshell, it's a server that is sending out correction data every second. There are thousands of sites around the globe that calculate the perturbations in the ionosphere and troposphere that decrease the accuracy of GNSS accuracy. Once the inaccuracies are known, correction values are encoded into data packets in the RTCM format. You, the user, don't need to know how to decode or deal with RTCM, you simply need to get RTCM from a source within 10km of your location into the RTK device. The NTRIP client logs into the server (also known as the NTRIP caster) and grabs that data, every second, and sends it over Bluetooth to the RTK device.
Where do I get RTK Corrections?
Be sure to see Correction Sources.
Don't have access to an NTRIP Caster or other RTCM correction source? There are a few options.
The SparkFun RTK Facet L-Band gets corrections via an encrypted signal from geosynchronous satellites. This device gets RTK Fix without the need for a WiFi or cellular connection.
Also, you can use a 2nd RTK product operating in Base mode to provide the correction data. Check out Creating a Permanent Base.
If you're the DIY sort, you can create your own low-cost base station using an ESP32 and a ZED-F9P breakout board. Check out How to Build a DIY GNSS Reference Station.
There are services available as well. Syklark provides RTCM coverage for $49 a month (as of writing) and is extremely easy to set up and use. Point One also offers RTK NTRIP service with a free 14 day trial and easy to use front end.