Mapit NTRIP Client

Coming soon

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 or TCP. This enables centimetre-level RTK positioning directly from the app - no third-party correction app required.

Android

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

Receiver	Manufacturer	Frequencies	Connection
RTK Portable Bluetooth Kit	ArduSimple	L1/L2	Bluetooth
simpleRTK2B Lite BT Kit	ArduSimple	L1/L2	Bluetooth
simpleRTK2B Budget + BT plugin	ArduSimple	L1/L2	Bluetooth
Reach M2	Emlid	L1/L2	Wi-Fi / TCP

Sample Professional GNSS Receivers

Receiver	Manufacturer	Frequencies	Connection
Globe	SXblue (Geneq)	L1/L2	Bluetooth + Wi-Fi
Smart / Platinum	SXblue (Geneq)	L1/L2	Bluetooth
Arrow Gold+ / Gold	Eos Positioning	L1/L2/L5	Bluetooth
Arrow 100+ / 100	Eos Positioning	L1/L2	Bluetooth
Reach RS3	Emlid	L1/L2	Wi-Fi / TCP
Flex	Bad Elf	L1/L2	Bluetooth
R12i / R10	Trimble	L1/L2/L5	Bluetooth + Wi-Fi
TDC650 / TDC600	Trimble	L1/L2	Bluetooth + Wi-Fi
GS18 T / GS18 I	Leica Geosystems	L1/L2/L5	Bluetooth + Wi-Fi
Zeno GG04 plus	Leica Geosystems	L1/L2	Bluetooth
iG8 / iG6	CHC Navigation	L1/L2/L5	Bluetooth + Wi-Fi
S900A / S980A	South Surveying	L1/L2/L5	Bluetooth + Wi-Fi
V200 / V100	Hi-Target	L1/L2/L5	Bluetooth + Wi-Fi

Sample Receivers That Do NOT Support RTK

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

Receiver	Manufacturer	Reason
SXblue II / II+	SXblue (Geneq)	L1-only, no RTCM input - supports SBAS (EGNOS/WAAS) only
GPS Pro / Pro+	Bad Elf	L1-only, no RTCM input
GLO / GLO 2	Garmin	L1-only, consumer-grade
Garmin GLO / GLO 2	L1-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

Field	Description	Example
Name	A label for this configuration	RTK2go - MyMount
Host	NTRIP caster hostname or IP	rtk2go.com
Port	Caster port number	2101
Mountpoint	The specific correction stream	NEAR_ME
Username	Caster username (if required)	user@email.com
Password	Caster password (if required)	none
NTRIP Version	V1 or V2 (most casters support both)	V2

Step 3: Select the Receiver Target

Choose where to forward the RTCM corrections:

Target	When to use
Bluetooth	Your receiver is connected via Bluetooth SPP (most common)
TCP	Your receiver is connected via TCP/IP or Wi-Fi
Test	No 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.

Setting	Description	Default
Send GGA	Enable automatic GGA position reporting to the caster	On
GGA interval	How 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

Caster	Host	Port	Notes
RTK2go	rtk2go.com	2101	Free community caster. Use your email as username, none as password. Browse mountpoints at rtk2go.com
EUREF-IP	euref-ip.net	2101	Free European reference stations. Register for access
Emlid Caster	caster.emlid.com	2101	Free for Emlid users

Commercial / Government Networks

Many countries operate free or subsidised RTK reference station networks:

Network	Country	Notes
OS Net	UK	Ordnance Survey - requires commercial license
SAPOS	Germany	State surveying authorities
CORS	USA	NGS Continuously Operating Reference Stations
SmartNet	UK/Europe	Leica Geosystems commercial network
Trimble VRS Now	Various	Trimble commercial VRS network

Using RTK2go (Free, Recommended for Testing)

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:

Attempt	Delay
1	5 seconds
2	10 seconds
3	20 seconds
4	40 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:

Column	Description
Time	When the message was received (HH:mm:ss.SSS)
Type	RTCM message type number and name (e.g., 1077 GPS MSM7)
Size	Message 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:

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

NMEA Tab

Displays raw NMEA sentences from the connected GNSS receiver:

Column	Description
Time	When the sentence was received
Sentence	Raw 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

Stream	Extension	Format	Example filename
RTCM	.rtcm3	Raw binary (can be opened in RTKCONV, RTKLIB)	rtcm_2026-02-23_163000.rtcm3
NMEA	.nmea	Plain text with CRLF line endings	nmea_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:

Stream	Rate	1 hour	8 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:

Quality	Meaning	Typical Accuracy
1	GPS (SPS) - no corrections	2-5 m
2	DGPS - SBAS/differential	0.5-2 m
4	RTK Fixed - full solution	1-3 cm
5	RTK Float - converging	10-30 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

Problem	Possible Cause	Solution
Cannot connect to caster	Wrong host/port, no internet	Verify caster details and mobile data
Connected but no data	Wrong mountpoint, authentication failed	Check mountpoint name, username/password
RTCM flowing but fix stays at 1	Receiver does not support RTK	Use a multi-frequency L1/L2 receiver with RTCM input
Fix stays at Float (5)	Poor satellite visibility, long baseline	Move to open sky, use a closer reference station
Frequent disconnections	Unstable mobile data	The client auto-reconnects; consider a caster with lower bandwidth requirements
Stream monitor shows no NMEA	Receiver not connected or not outputting	Check Bluetooth connection and receiver NMEA output configuration
Recording fails to start	Storage not accessible	Ensure Mapit-Data folder is set up and has write access

iOS

The NTRIP client is not available on iOS at this time.