The Bad Elf GNSS Surveyor uses an RTCM 2.3 feed delivered through an NTRIP client from a reference station to differentially correct the GPS signal and improve the positional accuracy reported. Using the built-in NTRIP client in the Bad Elf iOS application, one can connect directly to a reference station network. This write-up outlines the configuration of a typical NTRIP connection.

DGPS is a technique to improve the location accuracy of the Global Positioning System. DGPS uses a network of fixed, ground-based reference stations to broadcast the difference between the positions indicated by the GPS satellite systems and the known fixed positions.

The GNSS Surveyor only supports corrections of the coarse-acquisition (C/A) code (broadcast in the L1 signal)

The accuracy of DGPS decreases with distance from the reference station. If the user and the station are unable to see the same satellites, this problem is further exacerbated.

Where the GNSS Surveyor is configured to use differential correction data (e.g. via an RTCM stream), the receiver's coordinate frame will switch to whatever frame the source of correction data is using. For example, if the reference station is using NAD83 (2011) the locations provided by the GNSS Surveyor will shift to that datum.

Configuration Of The Bad Elf NTRIP Client

Bad Elf has had success with the NTRIP client for Android called Lefebure NTRIP Client. This NTRIP client can
be downloaded from the Google Play store using this link.

The following steps demonstrate the typical steps one would use to configure the Lefebure NTRIP client.

1. Ensure your Bad Elf has been paired with Android. Pairing is accomplished under Settings/Bluetooth

2. Start the Lefebure NTRIP Client and go to the settings screen. Select Receiver Settings. The receiver settings screen such as the one below is shown.
   

3. Click on the selection labeled Receiver Connection and select External Bluetooth.

4. Check the box for Auto-Enable Bluetooth.

5. Click on Bluetooth Device. A list of your paired Bluetooth devices is shown as below.
   

6. Select your Bad Elf receiver using the serial number found on the back of your Bad Elf.

7. Select the check boxes Auto-Enable Bluetooth and GPS Mock Locations
   

8. Return to the settings screen and select the NTRIP Settings
   

9. Enter your provider's Caster IP or domain name, Caster Port, Username, Password, and Data Stream (mount point)

10. Under the selection Reported Location, choose to Get from External Receiver

11. Return to the main menu, when ready click the Connect button.
    

12. When the connection is active, information will begin streaming in. Generally within 10 seconds, the connection will switch to DGPS.

13. The DGPS corrected positions are fed through Mock Location which means that any location aware app can use the corrected location data from this NTRIP client.