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NTRIP

Overview

NTRIP (Network Transport of RTCM via Internet Protocol) is an internet protocol for streaming RTCM (Radio Technical Commission for Maritime Services) packets from a nearby base station. These RTCM messages are forwarded to the SitePoint to aid in acquiring a more accurate location solution.

The app handles setting up the NTRIP connection, while the SDK parses the RTCM messages, which can then be sent to the SitePoint.

Some NTRIP providers require the device’s location to be sent upon connection, and others require regular location updates. These locations are assembled into GGA (Global Positioning System Fix Data) strings. The example app includes functions to create these strings in NtripGga.java.

Connecting to an NTRIP Service

The example app demonstrates a simplistic approach to establishing a connection with an NTRIP provider.

Once the connection is requested, the response is passed into parseAuthorized method of the NtripParser class to parse the authorization request.

Parsing Received RTCM Messages

After a successful connection, the parseRtcm method of the NtripParser class validates and filters the data, ignoring any messages that are not relevant for SitePoint aiding.

The parsed data is then available using the next method of the NtripParser class. For efficient writes, this data can have multiple messages, including messages that are split between returns from this method.

Sending RTCM Messages to the SitePoint

Write the prepared RTCM data to the RTCM characteristic using the writeCharacteristic method of the BluetoothGatt class.

The SitePoint will receive these messages and begin using them to aid in solving a more accurate solution. When successful, and given good satellite view, the status should change from 3D to float and then to fix, where the SitePoint will operate in its highest-accuracy mode.

Monitoring NTRIP Aiding Quality

The aidingQuality array of booleans in the Status class monitors whether the SitePoint used the recent RTCM messages.

For example, in the SQ Survey app, a graphical indicator shows this aiding quality with either a solid or empty rectangle for each position. This can be helpful for diagnosing issues obtaining a higher accuracy.

Remembering an NTRIP Service

The application stores and retrieves the last NTRIP service used for ease of use, even though it is not necessary for interacting with a SitePoint.

The NTRIP service model class is defined in app/src/main/proto/ntrip_service.proto and is used in the Ntrip class. This implementation requires the following plugins:

• libs.plugins.jetbrainsKotlinAndroid
• com.google.protobuf.

For more information on how to implement this using Android’s Proto DataStore, refer to the Android’s DataStore documentation.