The last newsletter provided “general” informa- tion about using the Internet to transfer RTK data to a GPS user and also described the features and benefits of using NTRIP.
This newsletter continues with this topic, but focuses on how to configure and use Sys- tem1200 to receive RTK data via the Internet and NTRIP.
Remember that the procedure described below only needs to be performed once – after this, the instrument is configured and can simply be turned on and used. As ever, if one day you plan to use the Internet and NTRIP to receive RTK data and then the next day will use a normal radio modem, then use different configuration sets for these different ways of working.
This newsletter is divided into 3 main parts: how to connect to the Internet, how to connect to a server on the Internet and how to receive RTK data from NTRIP.
STEP 1: CONNECTING TO THE INTERNET
As described last week, a GPRS (General Pa- cked Radio System) enabled device is no rmally used with System1200 to access the Internet. Almost any GPRS enabled device which can be operated using AT commands can be used with System1200. If you are using a Bluetooth en- abled GPRS device then also use the notes in newsletters 24 and 25 which describes how to use Bluetooth devices with System1200.
In the CONFIGURE Interfaces panel, highlight the Internet interface and press F3(EDIT) to access the CONFIGURE Internet Interface panel.
Ensure the Internet prompt is set to Yes and then select the port to which the GPRS device will be connected. You can now press F5(DEVCE) to access the CONFGURE GPRS Internet Devices panel which lists all default GPRS enabled devices supported by Sys- tem1200. If necessary, create a new device us- ing F2(NEW).
Having selected the appropriate device, press F1(CONT) to return to the CONFIGURE Internet Interface panel.
As described in the last newsletter, devices nor- mally connect to the Internet using dynamic IP addresses, so select Dynamic at the IP Ad- dress prompt.
Some telecom providers require a User Id and Password to be used in order to connect to the Internet via GPRS. If necessary, contact your telecom provider and enter these details and the User ID and Password prompts.
Once all settings are made, press F1(CONT) to return to the CONFIGURE Interfaces panel.
If a GPRS device is being used then the SIM card and the PIN code must be available and the so-called APN (Access Point Name) must be entered. To do this, highlight the Internet inter- face and press F4(CTRL) to access the CONFIGURE GPRS/Internet Connection panel.
The APN can be thought of as the “home page” of the telecom provider using GPRS for access- ing the Internet and can be obtained from your telecom provider.
If it is necessary to enter the PIN and/or PUK code then press F3(CODES) to access the CONFIGURE GSM Codes panel.
Having entered these parameters, press F1(CONT) to return to the CONFIGURE Inter- faces panel - the sensor will then automatically connect to the Internet. If successful, a message in the message line appears to be online and the Internet icon is shown.
The sensor is now online to the Internet, but since GPRS is being used and no data transfer has yet taken place no charges are being made.
STEP 2: CONNECTING TO THE SERVER
The sensor is now connected to the Internet, but is not connected to the server from where we want to receive RTK data – it could be said you are just swimming in the Internet. We now need to connect to a specific server on the Internet.
We have so far configured the Internet interface to use a GPRS device connected to a physical port on the System1200 instrument. This means there are now 3 additional “virtual” ports - NET1, NET2 and NET3 - which are available to be used by any interface on System1200. This means it is therefore possible for example to both receive RTK data as an RTK rover and send out NMEA messages simultaneously over the Internet.
In the CONFIGURE Interfaces panel, highlight the Real-Time interface and press F3(EDIT) to access the CONFIGURE Real-Time Mode panel and set the R-Time Mode to Rover.
At the Port prompt you can now see that the additional net ports are available – select one of these ports and press F1(CONT) to return to the CONFIGURE Interfaces panel.
We now need to configure the net port itself, so again highlight the Real-Time interface and press F4(CTRL) to access the CONFIGURE Set NET Port panel.
As already mentioned, when using GPRS to access the Internet it is only possible for the sensor to act as a TCP/IP Client due to the dy- namic IP address of the sensor. Therefore set the User prompt to Client and enter the IP Ad- dress of the Server to where the Net port should connect.
The TCP/IP Port of the Server through which the data is provided now needs to be entered. Each Server can have a number of ports and behind each port a different service can be available.
The Auto CONEC functionality is the same as the auto connect functionality when using GSM. In the Survey application as soon as F1(OCUPY) button is pressed the sensor will connect to the Server and RTK data will be re- ceived. F1(STOP) then stops the data transmis- sion. This functionality therefore minimises the amount of data received and therefore costs.
Once all settings are made, press F1(CONT) to store the settings and return to the CONFIGURE Interfaces panel.
It is now possible to connect to the server – highlight the Real-Time interface and press shift F4(CONEC).
If successful, a message in the message line appears to be online and the connected icon is shown.
STEP 3: CONFIGURING AN INTERFACE TO USE INTERNET AND USING NTRIP
So now the sensor is connected to the Internet and connected to a specific server. We now need to configure the sensor to access and use NTRIP services.
In the CONFIGURE Interfaces panel, again highlight the Real-Time interface and press F3(EDIT) to access the CONFIGURE Real-Time Mode panel. We have already configure this interface to be a rover and to use a NET port we only need to configure the NTRIP related settings.
Press F2(ROVER) to access the CONFIGURE Additional Rover Options panel and select the NTRIP page. Set the Use NTRIP prompt to Yes and configure the NTRIP relevant settings.
In order to access and receive RTK data from the NTRIP Caster a User Id and Pa ssword needs to be entered. If necessary, contact your NTRIP administrator to obtain a User ID and password.
It is also necessary to tell the NTRIP Caster from which NTRIP Server RTK data is required. This is possible by entering the Mountpoint name at the Mountpnt prompt. As described in the last newsletter, the Mountpoint identifies the NTRIP Server (the RTK reference station), which pro- vides the RTK data to the NTRIP Caster.
If the name of the Mountpoint is not known then the NTRIP Source-Table can be downloaded to the sensor by pressing the F5(SRCE) button – the sensor will connect to the NTRIP Caster and request the NTRIP Source-Table. Once the download of the source-table is finished the con- nection to the NTRIP caster is closed and the CONFIGURE NTRIP Source-Table panel is automatically is accessed which shows all available Mountpoints.
A Mountpoint can be selected with F1(CONT). To view information about a particular Mount- point, press F3(INFO) to access the CONFIGURE Mountpoint panel.
Some of this information is “general” information and some of it (such as the RTK format) can be used to correctly configure settings in the CONFIGURE Real-Time Mode panel. F2(PREV) and F3(NEXT) displays information about the previous or next Mountpoint in the source-table.
Once the appropriate Mountpoint has been se- lected and the configuration of the real-time in- terface is complete, then surveying can begin.
The shift F3(CONEC) and shift F3(DISCO) button in the Survey and other applications (Stakeout, Reference Line, Reference Plane etc) allows the instrument to connect and disconnect to the NTRIP Caster Server.
Appropriate messages will be shown if connec- tion is not possible due to a wrong User ID or password or if the sensor is not allowed to ac- cess the NTRIP services or if the chosen Mount- point is not available.
Once the connection to the Caster is established and the user is authorized to receive RTK data, then RTK data will be streamed to the sensor and the RTK icon will flash to indicate data is being received – the same as when receiving RTK data via a radio or GSM modem
Perhaps the most important point to re-iterate here is that the configuration of the System1200 instrument to connect to the Internet and use NTRIP needs only to be made once.
After this, connection is as simple as pressing the shift F3(CONEC) button (even this is not necessary if using the automatic connection functionality).