Using differential corrections with OxTS units

Corrections can be supplied to the OxTS units in both real-time and in post process. The schematic below shows the difference between the two

When using live differential corrections there are a couple of distinct factors that we have to consider:

1. Source of the corrections
2. Medium over which the corrections are sent
3. The format of those corrections

From a base station:

Important things to remember when using a base station - if you require repeatable data, then the location of the antenna must not move. If the antenna moves, the location of the remote receivers also moves.

 Via NTRIP

Over Ethernet/WiFi

Requirements:

• RT unit with firmware version of at least 150527
• Feature code for the unit to use Network DGPS (contact info@oxts.com if you need more information)
• Base station that is outputting RTCMv3 over Ethernet/WiFi using the UDP protocol. You can use either an RT Base S or any other system that has the ability to send RTCMv3 packets over Ethernet.
• Method to send the corrections to the RT from the Base Station (Usually a wireless access point connected to a larger network)

Process: 

1. Apply the feature codes to the system you wish you test using the guide in the email, there will be instruction on how to do this when you receive the codes

2. Ensure the RT is connected via Ethernet to the network that will be carrying the RTCMv3 network correction broadcast (Using a switch is best, that way you can connect the RT, PC and source of corrections at the same time)

3. Configure the unit as per normal up until the options page in NAVConfig

4. At the options page you should add the following messages in the advanced commands section:

Messages:

Please note that the following are only compatible with RT2000, RT3000 and RT4000

NAVconfig now has options in the Differential page of the GUI to support network correction transmission and receipt

->gps1:INTERFACEMODE COM1 RTCMV3 NOVATEL OFF
-diff_format_rtcm
-diff_udp_wrapper_plain
-diff_udp_ipXXX.XXX.XXX.XXX
-diff_udp_portYYYY
-diff_send_gps1

5. In place of the XXX.XXX.XXX.XXX, put the IP address of the Base station (or Base S)

6. In place of the YYYY put the destination port that those corrections are getting sent out on (by default this is 50472 for the Base S)

7. Apply the configuration to the unit as per normal

8. Ensure that the base station is outputting the messages over the network. For the RT Base S , select:

9. View the system in NAVdisplay and you should see that the unit is receiving correction by confirming the Diff age and the Position Mode.

In Post Process

If you are not able to receive corrections in real time, you can process with a RINEX file.