An NTRIP Server is the software element which stands between the GNSS reference station device and the NTRIP Caster. Its functional purpose (setting aside its rather ill chosen name, which is more or less universally acknowledged as poor choice at this point in time) is to reach out to the NTRIP Caster using HTTP over TCP/IP and establish a connection where data can be pushed from the GNSS device to the NTRIP Caster. Traditional NTRIP Casters must wait until the external NTRIP Servers make contact with them in this way to create their data streams (this is not true for SNIP).
NTRIP Servers are typically GNSS reference stations of various quality levels with a thin layer of software to connect to and push data out to a Caster over an internet connection using HTTP. These days, nearly all GNSS devices which were intended for use as reference stations have the core NTRIP server functionality built directly into them. Hence the red line shown above encloses both the data source (the actual GNSS device) and the “server” element in one physical device.
Built in NTRIP Servers
If your GNSS device comes with an RJ-45 plug built into it, there is a high chance that it already has NTRIP Server abilities. Contact your equipment dealer to see if this is a feature you must enable in order to use. Once they have told you the fee to turn this feature on, then please read on.
Most GNSS devices also provide a serial output and this can easily be used to provide its RTCM observation message to others. On some GNSS devices this same data is only available in a raw or proprietary format, as is often the case in lost cost devices. In still other GNSS devices the ability to send data in the RTCM format itself is an additional paid option. As an example of a middle ground approach, Hemisphere GNSS charges an additional fee for providing outputs formatted into RTCM message, but freely provides an NTRIP Server (but not a caster) as part of their PocketMax3 utility tool. [You can easily connect their NTRIP Server to a SNIP caster.] Business models vary widely.
Publicly Available NTRIP Servers
The “thin layer of software” which makes up the NTRIP Server is easily implemented on a PC and several free tools are available which can provide this service. RTKLIB is one of these. And you can use its STRSVR tool to gather data from a serial port, and then send it out to an NTRIP Caster such as SNIP. RTKLIB also provides some unique message format translations for several GNSS vendors allowing a user to translate raw messages into RTCM rev 3 message for use by the Caster and others.
Eliminating the NTRIP Server Element
Because the layer of software involved is simple, and often can be easily added to a serial ports functionality, some Caster designs (including SNIP) just combine the Server element along with the Caster element in a single design. This hybrid design allows connecting one or more serial ports, as well as translating the data provided on those ports, in one convenient application.
Need an NTRIP Caster that is also an NTRIP Server? We suggest you use SNIP.