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Mapit NTRIP Client

Subscription required

The NTRIP client requires a Mapit Pro Plus subscription. See Mapit Pro Plus for details.

Mapit GIS includes a built-in NTRIP client that connects to any NTRIP caster over the internet, receives RTCM correction data in real time, and forwards it to your external GNSS receiver over Bluetooth, BLE, or TCP. This enables centimetre-level RTK positioning directly from the app - no third-party correction app required.

How RTK Corrections Work​

Real-Time Kinematic (RTK) positioning works by combining satellite observations from your receiver (the rover) with correction data from a nearby reference station (base station) whose position is precisely known. The reference station continuously computes the difference between its known position and its satellite-derived position, then broadcasts these corrections as RTCM messages.

Your receiver applies these corrections to its own observations and resolves carrier-phase ambiguities, achieving accuracies of 1-3 cm horizontally.

Reference Station
(known position)
│
▼
NTRIP Caster
(relay server)
│
▼
Mapit GIS
(NTRIP client)
│
▼
GNSS Receiver
(computes RTK fix)
│
▼
Corrected Position
│
▼
Mapit GIS Location

NTRIP (Networked Transport of RTCM via Internet Protocol) is the standard protocol for streaming RTCM corrections over the internet. An NTRIP caster is a server that receives data from one or more reference stations and distributes it to connected clients.

Hardware Requirements​

Compatible receiver required

The NTRIP client forwards raw RTCM correction data to your GNSS receiver. The receiver itself must be capable of processing these corrections and computing an RTK solution. Not all receivers support RTK.

What You Need​

  1. A multi-frequency (L1/L2) RTK-capable GNSS receiver that accepts RTCM input over Bluetooth or TCP/Wi-Fi
  2. Mobile data or Wi-Fi on your Android device to connect to the NTRIP caster
  3. An NTRIP caster account (free or paid, depending on the provider)

Why L1/L2 Matters​

Single-frequency (L1-only) receivers cannot resolve carrier-phase ambiguities reliably enough for centimetre-level RTK. Multi-frequency receivers track signals on two or more bands (L1 + L2, or L1 + L5), which allows them to:

  • Resolve integer ambiguities faster (shorter time to first fix)
  • Maintain a fix over longer baselines (distance to the reference station)
  • Achieve centimetre-level accuracy in typical field conditions

Sample Compatible Receivers​

Below are sample receivers that are known to support RTK corrections. This list is not exhaustive - any receiver that accepts RTCM3 input over Bluetooth SPP or TCP and outputs NMEA should be compatible with the Mapit NTRIP client.

Sample Budget / Development Boards​

ReceiverManufacturerFrequenciesConnection
RTK Portable Bluetooth KitArduSimpleL1/L2Bluetooth
simpleRTK2B Lite BT KitArduSimpleL1/L2Bluetooth
simpleRTK2B Budget + BT pluginArduSimpleL1/L2Bluetooth
Reach M2EmlidL1/L2Wi-Fi / TCP

Sample Professional GNSS Receivers​

ReceiverManufacturerFrequenciesConnection
GlobeSXblue (Geneq)L1/L2Bluetooth + Wi-Fi
Smart / PlatinumSXblue (Geneq)L1/L2Bluetooth
Arrow Gold+ / GoldEos PositioningL1/L2/L5Bluetooth
Arrow 100+ / 100Eos PositioningL1/L2Bluetooth
Reach RS3EmlidL1/L2Wi-Fi / TCP
FlexBad ElfL1/L2Bluetooth
R12i / R10TrimbleL1/L2/L5Bluetooth + Wi-Fi
TDC650 / TDC600TrimbleL1/L2Bluetooth + Wi-Fi
GS18 T / GS18 ILeica GeosystemsL1/L2/L5Bluetooth + Wi-Fi
Zeno GG04 plusLeica GeosystemsL1/L2Bluetooth
iG8 / iG6CHC NavigationL1/L2/L5Bluetooth + Wi-Fi
S900A / S980ASouth SurveyingL1/L2/L5Bluetooth + Wi-Fi
V200 / V100Hi-TargetL1/L2/L5Bluetooth + Wi-Fi

Sample Receivers That Do NOT Support RTK​

These receivers are supported by Mapit GIS for standard positioning but cannot process RTCM corrections:

ReceiverManufacturerReason
SXblue II / II+SXblue (Geneq)L1-only, no RTCM input - supports SBAS (EGNOS/WAAS) only
GPS Pro / Pro+Bad ElfL1-only, no RTCM input
GLO / GLO 2GarminL1-only, consumer-grade
Garmin GLO / GLO 2L1-only, consumer-grade

Configuring the NTRIP Client​

Step 1: Open NTRIP Settings​

  1. Open Settings from the main menu
  2. Navigate to NTRIP Corrections
  3. Tap Add Configuration to create a new caster profile

Step 2: Enter Caster Details​

FieldDescriptionExample
NameA label for this configurationRTK2go - MyMount
HostNTRIP caster hostname or IPrtk2go.com
PortCaster port number2101
MountpointThe specific correction streamNEAR_ME
UsernameCaster username (if required)user@email.com
PasswordCaster password (if required)none
NTRIP VersionV1 or V2 (most casters support both)V2

Step 3: Select the Receiver Target​

Choose where to forward the RTCM corrections:

TargetWhen to use
BluetoothYour receiver is connected via Bluetooth SPP (most common)
TCPYour receiver is connected via TCP/IP or Wi-Fi
TestNo forwarding - just monitor the stream for testing

Step 4: Configure GGA Sending​

Many NTRIP casters require your approximate position (via a GGA sentence) to select the nearest reference station or to provide Virtual Reference Station (VRS) corrections.

SettingDescriptionDefault
Send GGAEnable automatic GGA position reporting to the casterOn
GGA intervalHow often to send your position (seconds)10
tip

Leave GGA sending enabled unless you are connecting to a single-base station caster that does not require it. VRS networks always require GGA to generate corrections for your location.

Step 5: Connect​

Tap Connect. The app will:

  1. Start a foreground service with a persistent notification
  2. Connect to the NTRIP caster
  3. Authenticate and request the mountpoint stream
  4. Begin receiving RTCM correction data
  5. Forward RTCM data to the selected receiver target
  6. Send GGA position updates at the configured interval

The notification shows the connection status and current data rate (KB/s).

Notification permissions

On Android 13+, the app needs notification permission to display the foreground service notification. If you denied this permission, go to Android Settings > Apps > Mapit GIS > Notifications and enable it. Without notifications enabled, Android may kill the NTRIP service while the app is in the background.

Finding an NTRIP Caster​

Free Casters​

CasterHostPortNotes
RTK2gortk2go.com2101Free community caster. Use your email as username, none as password. Browse mountpoints at rtk2go.com
EUREF-IPeuref-ip.net2101Free European reference stations. Register for access
Emlid Castercaster.emlid.com2101Free for Emlid users

Commercial / Government Networks​

Many countries operate free or subsidised RTK reference station networks:

NetworkCountryNotes
OS NetUKOrdnance Survey - requires commercial license
SAPOSGermanyState surveying authorities
CORSUSANGS Continuously Operating Reference Stations
SmartNetUK/EuropeLeica Geosystems commercial network
Trimble VRS NowVariousTrimble commercial VRS network

RTK2go is the easiest way to get started:

  1. Visit rtk2go.com to browse available mountpoints near you
  2. In Mapit GIS, create a new NTRIP configuration:
    • Host: rtk2go.com
    • Port: 2101
    • Username: your email address
    • Password: none
  3. The app will fetch the source table and list available mountpoints
  4. Mountpoints are sorted by distance from your current position - select the nearest one
  5. Tap Connect
tip

The closer the reference station to your position, the better. RTK accuracy degrades with baseline length. Aim for a station within 30 km for reliable RTK Fixed solutions.

Connection Management​

Auto-Reconnect​

If the connection drops (network interruption, caster restart), the app automatically reconnects with exponential backoff:

AttemptDelay
15 seconds
210 seconds
320 seconds
440 seconds
5+60 seconds (max)

After 20 failed attempts, the service stops automatically.

Multiple Configurations​

You can save multiple NTRIP caster profiles - for example, one for your local RTK network and one for RTK2go as a fallback. Only one connection can be active at a time.

Disconnecting​

Tap Disconnect in the NTRIP settings, or tap the Stop action on the foreground notification. Disconnecting stops all RTCM forwarding and closes any active stream log files.

Monitoring Streams​

The Stream Monitor screen provides real-time visibility into the RTCM and NMEA data flowing through the app.

Open it from Settings > NTRIP Corrections > Stream Monitor.

RTCM Tab​

Displays decoded RTCM3 messages in real time:

ColumnDescription
TimeWhen the message was received (HH:mm:ss.SSS)
TypeRTCM message type number and name (e.g., 1077 GPS MSM7)
SizeMessage size in bytes

A summary bar at the top shows:

  • Total messages received
  • Number of unique message types
  • Messages per second

Common RTCM3 message types you may see:

TypeDescription
1004GPS L1/L2 observations (legacy)
1005/1006Station coordinates
1012GLONASS L1/L2 observations (legacy)
1033Receiver/antenna descriptor
1074-1077GPS MSM4-MSM7 (modern, preferred)
1084-1087GLONASS MSM4-MSM7
1094-1097Galileo MSM4-MSM7
1124-1127BeiDou MSM4-MSM7
1230GLONASS code-phase biases
4072Reference station PNT (u-blox proprietary)

NMEA Tab​

Displays raw NMEA sentences from the connected GNSS receiver:

ColumnDescription
TimeWhen the sentence was received
SentenceRaw NMEA sentence (e.g., $GPGGA,...)

This is useful for verifying that your receiver is outputting data and checking the fix quality field in real time.

Clearing the Monitor​

Tap the delete icon in the top bar to clear all messages in the current tab. The monitor holds up to 500 messages per tab.

Recording Streams to File​

You can record RTCM and NMEA streams to files in the Mapit-Data/Logs/ directory for post-session diagnostics, quality analysis, or post-processing.

Starting a Recording​

  1. Open the Stream Monitor
  2. Select the RTCM or NMEA tab
  3. Tap the record button (circle icon) in the top bar
  4. The icon turns to a red stop icon and a status bar appears showing bytes written

Each tab has an independent record button - you can record RTCM and NMEA simultaneously or separately.

Recording Status Bar​

When recording is active, a red status bar appears below the tab row:

Recording · 2.4 MB

If recording stops automatically, the bar shows the reason:

Stopped: Max file size reached

File Format and Naming​

StreamExtensionFormatExample filename
RTCM.rtcm3Raw binary (can be opened in RTKCONV, RTKLIB)rtcm_2026-02-23_163000.rtcm3
NMEA.nmeaPlain text with CRLF line endingsnmea_2026-02-23_163000.nmea

The timestamp in the filename is when recording started.

File Size Limits​

Each log file has a maximum size of 50 MB (approximately 8 hours of combined recording). When the limit is reached, recording stops automatically with a notification. Typical sizes:

StreamRate1 hour8 hours
RTCM (raw binary)~1 KB/s~3.6 MB~29 MB
NMEA (raw text)~0.6 KB/s~2.3 MB~18 MB
Combined~1.6 KB/s~6 MB~47 MB

Recording Persists Across Screens​

Recording is managed by a background singleton - it continues even when you close the Stream Monitor screen. Reopening the monitor will show the current recording status. Recording stops when:

  • You tap the stop button
  • The 50 MB file size limit is reached
  • You disconnect from the NTRIP caster

Post-Processing with RTKLIB​

The recorded .rtcm3 files can be converted and post-processed using RTKLIB (free, open-source):

  1. Open RTKCONV to convert .rtcm3 to RINEX observation files
  2. Use RTKPOST to post-process against a base station for improved accuracy
  3. The .nmea files can be opened in any text editor or imported into GIS software

Understanding Fix Quality​

Once RTCM corrections are being applied by your receiver, you will see the fix quality change in the GPS Info sheet:

QualityMeaningTypical Accuracy
1GPS (SPS) - no corrections2-5 m
2DGPS - SBAS/differential0.5-2 m
4RTK Fixed - full solution1-3 cm
5RTK Float - converging10-30 cm

The progression is typically: 1 (SPS) → 5 (Float) → 4 (Fixed). Time to first fix depends on satellite visibility, baseline length, and the number of satellites tracked on both frequencies. Expect 10-60 seconds under good conditions.

If the fix quality remains at 1 after connecting to NTRIP:

  • Verify your receiver supports RTCM input (see sample compatible receivers above)
  • Check that the receiver target is set correctly (Bluetooth or TCP)
  • Confirm the mountpoint is providing corrections for your region
  • Ensure the baseline to the reference station is within range (< 30 km recommended)

For a detailed explanation of all fix types and how accuracy is computed, see RTK and Fix Types.

Typical Field Workflow​

  1. Before going to the field:

    • Create an NTRIP configuration with your caster details
    • Verify your receiver is paired via Bluetooth (see Connecting a Receiver)
    • Ensure you have mobile data coverage at the survey site

  2. At the survey site:

    • Power on your GNSS receiver and connect via Bluetooth
    • Open Settings > NTRIP Corrections and tap Connect
    • Wait for the notification to show a data rate (e.g., MyMount - 1.2 KB/s)
    • Open the Stream Monitor to verify RTCM messages are flowing
    • Check the GPS Info sheet - wait for fix quality to reach RTK Fixed (4)
    • Optionally start recording the RTCM/NMEA streams for diagnostics
    • Begin data collection

  3. After the survey:

    • Disconnect from NTRIP (or it disconnects automatically when you stop the service)
    • Log files (if recording was active) are saved in Mapit-Data/Logs/
    • Recorded .rtcm3 and .nmea files can be used for post-processing or quality verification

Troubleshooting​

ProblemPossible CauseSolution
Cannot connect to casterWrong host/port, no internetVerify caster details and mobile data
Connected but no dataWrong mountpoint, authentication failedCheck mountpoint name, username/password
RTCM flowing but fix stays at 1Receiver does not support RTKUse a multi-frequency L1/L2 receiver with RTCM input
Fix stays at Float (5)Poor satellite visibility, long baselineMove to open sky, use a closer reference station
Frequent disconnectionsUnstable mobile dataThe client auto-reconnects; consider a caster with lower bandwidth requirements
Stream monitor shows no NMEAReceiver not connected or not outputtingCheck Bluetooth connection and receiver NMEA output configuration
Recording fails to startStorage not accessibleEnsure Mapit-Data folder is set up and has write access