[{"data":1,"prerenderedAt":1103},["ShallowReactive",2],{"knowledge-page-en-\u002Flearn\u002Fwhat-is-rtcm":3},{"article":4,"posts":381,"relatedPosts":382},{"id":5,"title":6,"author":7,"body":8,"category":366,"cover":367,"description":368,"extension":369,"meta":370,"navigation":371,"path":372,"publishedAt":373,"relatedArticles":374,"seo":377,"stem":378,"updatedAt":379,"__hash__":380},"knowledge_en\u002Fen\u002Flearn\u002Fwhat-is-rtcm.md","What is RTCM and which version do I need?","Wilko",{"type":9,"value":10,"toc":352},"minimark",[11,16,25,28,31,52,56,59,88,95,99,106,109,229,234,237,240,244,247,251,254,260,264,267,294,298,301,304,309,312,346],[12,13,15],"h2",{"id":14},"what-is-rtcm","What is RTCM?",[17,18,19,20,24],"p",{},"RTCM stands for ",[21,22,23],"strong",{},"Radio Technical Commission for Maritime Services"," — the organisation that defined the standard format for transmitting GNSS correction data between a reference station and a rover. Despite the maritime origin, RTCM is used everywhere: surveying, agriculture, drones, autonomous vehicles and construction.",[17,26,27],{},"When your RTK receiver connects to an NTRIP server, the server streams a continuous series of RTCM messages. Each message contains correction data for a specific satellite system (GPS, GLONASS, Galileo, BeiDou) or for specific information types (satellite orbits, clock errors, phase biases). Your receiver reads these messages and applies the corrections to its own satellite observations to compute a centimetre-accurate position.",[17,29,30],{},"RTCM is an open standard. This means any receiver that claims RTCM support will work with any RTCM-compatible correction service — regardless of brand.",[32,33,35,40,44,48],"text-grid",{"additionalstyles":34},"mt-[60px]",[36,37],"text-grid-item",{"text":38,"title":39},"The current correction-data standard","RTCM3",[36,41],{"text":42,"title":43},"Modern multi-signal message format","MSM",[36,45],{"text":46,"title":47},"Main MSM levels you will encounter","4",[36,49],{"text":50,"title":51},"Works across compatible brands","Open",[12,53,55],{"id":54},"rtcm2-vs-rtcm3","RTCM2 vs RTCM3",[17,57,58],{},"There are two major versions of the RTCM standard. The difference matters for older equipment.",[60,61,62,76],"cards",{"additionalstyles":34},[63,64,68,71],"card",{"additionalstyles":65,"color":66,"title":67},"h-full","orange","RTCM 2.x — Legacy",[17,69,70],{},"Developed in the 1990s. Supports GPS only (no GLONASS, Galileo or BeiDou). Uses a fixed message structure that wastes bandwidth. Still found on very old receivers — pre-2010 equipment.",[17,72,73],{},[21,74,75],{},"Not recommended",[63,77,80,83],{"additionalstyles":65,"color":78,"title":79},"green","RTCM 3.x — Current standard",[17,81,82],{},"Introduced in 2004, continuously updated. Supports all satellite constellations. Uses efficient binary encoding. Includes MSM (Multiple Signal Messages) for multi-frequency data. Used by every modern receiver and correction service.",[17,84,85],{},[21,86,87],{},"Use this",[63,89,92],{"additionalstyles":34,"color":90,"title":91},"primary","Which version do you have?",[17,93,94],{},"If your receiver was manufactured after 2010 and supports multi-constellation GNSS, it uses RTCM3. You do not need to think about RTCM2 unless you are working with genuinely old hardware.",[12,96,98],{"id":97},"msm-types-explained-msm4-msm5-msm7","MSM types explained — MSM4, MSM5, MSM7",[17,100,101,102,105],{},"Within RTCM3, the most important message type for modern RTK is MSM — ",[21,103,104],{},"Multiple Signal Messages",". MSM messages carry satellite observations in a compact, extensible format that supports all constellations and multiple frequencies simultaneously.",[17,107,108],{},"There are several MSM levels. The three you will encounter in NTRIP sourcetables are MSM4, MSM5 and MSM7.",[110,111,112,131],"table",{},[113,114,115],"thead",{},[116,117,118,122,125,128],"tr",{},[119,120,121],"th",{},"Type",[119,123,124],{},"Data included",[119,126,127],{},"Bandwidth",[119,129,130],{},"Best for",[132,133,134,154,173,192,211],"tbody",{},[116,135,136,142,145,148],{},[137,138,139],"td",{},[21,140,141],{},"MSM4",[137,143,144],{},"Pseudorange + carrier phase (compressed)",[137,146,147],{},"Low",[137,149,150,153],{},[21,151,152],{},"Recommended"," — Most receivers: Emlid, u-blox, generic NTRIP clients",[116,155,156,161,164,167],{},[137,157,158],{},[21,159,160],{},"MSM5",[137,162,163],{},"MSM4 data + Doppler observations",[137,165,166],{},"Medium",[137,168,169,172],{},[21,170,171],{},"DJI required"," — DJI drones and some high-rate applications",[116,174,175,180,183,186],{},[137,176,177],{},[21,178,179],{},"MSM7",[137,181,182],{},"Full precision pseudorange + carrier phase (extended)",[137,184,185],{},"High",[137,187,188,191],{},[21,189,190],{},"High-end"," — Trimble, Leica, Septentrio and survey-grade receivers",[116,193,194,199,202,205],{},[137,195,196],{},[21,197,198],{},"MSM6",[137,200,201],{},"MSM5 data at extended precision",[137,203,204],{},"Medium-high",[137,206,207,210],{},[21,208,209],{},"Rare"," — not commonly offered by NTRIP services",[116,212,213,218,221,223],{},[137,214,215],{},[21,216,217],{},"1004 \u002F 1012",[137,219,220],{},"Legacy GPS + GLONASS observations (pre-MSM)",[137,222,147],{},[137,224,225,228],{},[21,226,227],{},"Legacy"," — old receivers that do not support MSM",[230,231,233],"h3",{"id":232},"msm4-the-universal-default","MSM4 — the universal default",[17,235,236],{},"MSM4 contains everything a modern dual-frequency RTK receiver needs to compute a Fix. It includes pseudorange measurements and carrier phase observations for all tracked satellites across all constellations — GPS, GLONASS, Galileo, BeiDou, QZSS. The compressed format keeps bandwidth low, which matters for mobile data connections in the field.",[17,238,239],{},"If you are unsure which MSM level to use, start with MSM4. It works correctly with Emlid, u-blox ZED-F9P, Ardusimple and most generic NTRIP clients.",[230,241,243],{"id":242},"msm5-required-for-dji","MSM5 — required for DJI",[17,245,246],{},"MSM5 adds Doppler observations to the MSM4 data. DJI's RTK implementation specifically requires Doppler data to initialise correctly. Using MSM4 with a DJI drone will result in Float or no Fix even when the connection appears successful. Always use MSM5 or higher for DJI.",[230,248,250],{"id":249},"msm7-for-professional-survey-equipment","MSM7 — for professional survey equipment",[17,252,253],{},"MSM7 provides the same observations as MSM4 but at extended precision — the measurements are stored with more decimal places. For Trimble, Leica and Septentrio receivers that work at sub-centimetre level, MSM7 squeezes out the last bit of accuracy. The bandwidth cost is roughly twice that of MSM4, which is acceptable on modern mobile connections but worth knowing in bandwidth-limited environments.",[63,255,257],{"additionalstyles":34,"color":66,"title":256},"Wrong MSM type causes Float, not an error",[17,258,259],{},"If you use MSM4 with a DJI drone, the correction stream flows normally and the connection shows as successful — but the drone stays on Float. There is no error message. The only sign something is wrong is the absence of Fix. If your DJI device never reaches Fix, switching from MSM4 to MSM5 is the first thing to try.",[12,261,263],{"id":262},"which-mountpoint-for-my-device","Which mountpoint for my device?",[17,265,266],{},"Select the mountpoint that matches your device and situation.",[60,268,269,274,278,282,286,290],{"additionalstyles":34},[270,271],"cards-item",{"text":272,"title":273},"Standard survey rover — choose an MSM4 mountpoint. Use VRS when you are more than 30 km from the nearest physical station.","Emlid Reach RS2+, RS3, RS4",[270,275],{"text":276,"title":277},"Network rover only — choose an MSM4 mountpoint. VRS is strongly recommended for long baselines.","Emlid Reach RX \u002F RX2",[270,279],{"text":280,"title":281},"Mavic 3E, M300, M30 RTK — choose MSM5 or higher. DJI requires Doppler observations to reach Fix.","DJI drone",[270,283],{"text":284,"title":285},"Professional survey grade — choose MSM7 to use the extended precision available in high-end receivers.","Trimble \u002F Leica",[270,287],{"text":288,"title":289},"Ardusimple, SparkFun and DIY setups — choose MSM4, the compatible low-bandwidth default.","u-blox ZED-F9P",[270,291],{"text":292,"title":293},"More than 30 km from a station — choose a VRS mountpoint and make sure your NTRIP client sends GGA.","Any device — long baseline",[12,295,297],{"id":296},"reading-a-sourcetable","Reading a sourcetable",[17,299,300],{},"When you connect to an NTRIP server without specifying a mountpoint, the server returns a sourcetable — a list of all available correction streams. Understanding how to read it helps you choose the right stream.",[17,302,303],{},"A typical sourcetable entry looks like this:",[305,306],"terminal-box",{"additionalstyles":307,"items":308},"mt-[30px]","|STR;RTCM3_NL;Netherlands;RTCM 3.3;1004,1006,1008,1012,1019,1020,1033,1042,1045,1046,1077,1087,1097,1107,1127;2;GPS+GLO+GAL+BDS+SBAS;RTKsub;NLD;52.37;4.89;1;1;GEODNET;none;B;N;0;",[17,310,311],{},"The key fields to read:",[313,314,315,322,328,334,340],"ul",{},[316,317,318,321],"li",{},[21,319,320],{},"RTCM3_NL"," — the mountpoint name you enter in your NTRIP client",[316,323,324,327],{},[21,325,326],{},"RTCM 3.3"," — the RTCM version used by this stream",[316,329,330,333],{},[21,331,332],{},"1077, 1087, 1097, 1107, 1127"," — MSM7 message numbers for GPS, GLONASS, Galileo, QZSS and BeiDou. Numbers ending in 4 = MSM4, 5 = MSM5, 7 = MSM7",[316,335,336,339],{},[21,337,338],{},"GPS+GLO+GAL+BDS"," — satellite constellations included in the stream",[316,341,342,345],{},[21,343,344],{},"52.37;4.89"," — approximate latitude and longitude of the reference station",[63,347,349],{"additionalstyles":34,"color":90,"title":348},"You do not need to decode sourcetables manually",[17,350,351],{},"Most NTRIP clients have a “Get Mountpoints” button that downloads and displays the sourcetable in a readable format. Use that instead of reading raw entries. The table above is for reference if you ever need to inspect the raw data.",{"title":353,"searchDepth":354,"depth":354,"links":355},"",2,[356,357,358,364,365],{"id":14,"depth":354,"text":15},{"id":54,"depth":354,"text":55},{"id":97,"depth":354,"text":98,"children":359},[360,362,363],{"id":232,"depth":361,"text":233},3,{"id":242,"depth":361,"text":243},{"id":249,"depth":361,"text":250},{"id":262,"depth":354,"text":263},{"id":296,"depth":354,"text":297},"learn","learn\u002Fwhat-is-rtcm.webp","RTCM is the universal language that RTK correction services and receivers use to communicate. Choosing the wrong version does not stop corrections from flowing — but choosing the right one gives you faster Fix and better accuracy.","md",{},true,"\u002Fen\u002Flearn\u002Fwhat-is-rtcm","2026-07-25",[375,376],"\u002Fen\u002Flearn\u002Fwhat-is-ntrip","\u002Fen\u002Flearn\u002Fwhat-is-vrs",{"title":6,"description":368},"en\u002Flearn\u002Fwhat-is-rtcm",null,"a_cAu34GtgnNoMHTal1dPWChkbkVZLWcgH8uV_0MZBA",[],[383,707],{"id":384,"title":385,"author":7,"body":386,"category":366,"cover":700,"description":701,"extension":369,"meta":702,"navigation":371,"path":375,"publishedAt":703,"relatedArticles":379,"seo":704,"stem":705,"updatedAt":379,"__hash__":706},"knowledge_en\u002Fen\u002Flearn\u002Fwhat-is-ntrip.md","What is NTRIP and how does it work?",{"type":9,"value":387,"toc":688},[388,392,395,398,415,419,422,446,450,453,457,465,468,472,475,479,519,525,529,532,633,637,655,661,665,668,682],[12,389,391],{"id":390},"what-ntrip-stands-for","What NTRIP stands for",[17,393,394],{},"NTRIP stands for Networked Transport of RTCM via Internet Protocol. Unpacking the name tells you exactly what it does: it takes RTCM correction data — the standard format for RTK corrections — and delivers it over the internet using standard HTTP-based communication.",[17,396,397],{},"NTRIP was developed by the German Federal Agency for Cartography and Geodesy (BKG) in the early 2000s and became the global standard for internet-based RTK correction delivery. Today it is used by every major correction network, every modern RTK receiver and virtually every field survey software package.",[32,399,400,404,408,411],{"additionalstyles":34},[36,401],{"text":402,"title":403},"Standard TCP port","2101",[36,405],{"text":406,"title":407},"Protocol base","HTTP",[36,409],{"text":410,"title":39},"Data format carried",[36,412],{"text":413,"title":414},"Correction latency","\u003C1 s",[12,416,418],{"id":417},"the-three-components","The three components",[17,420,421],{},"NTRIP has three distinct roles — caster, server and client — that together form the correction delivery chain. Understanding these helps you configure your equipment correctly and diagnose connection problems.",[423,424,425,430,434,439,442],"flow-diagram",{"additionalstyles":34},[426,427],"flow-card",{"text":428,"title":429},"NTRIP Server","Reference station",[431,432],"flow-connector",{"text":433},"RTCM3 over internet",[426,435],{"text":436,"title":437,":highlighted":438},"Central hub","NTRIP Caster","true",[431,440],{"text":441},"RTCM3 stream on demand",[426,443],{"text":444,"title":445},"NTRIP Client","Your device",[230,447,449],{"id":448},"ntrip-server-the-reference-station-side","NTRIP Server — the reference station side",[17,451,452],{},"The NTRIP Server is the software running at each physical reference station. It reads the raw GNSS observations from the receiver and pushes them continuously to the caster over the internet. A reference station broadcasts its data to the caster 24 hours a day, typically at 1-second intervals. You never interact with the server directly — it operates invisibly in the background.",[230,454,456],{"id":455},"ntrip-caster-the-central-hub","NTRIP Caster — the central hub",[17,458,459,460,464],{},"The NTRIP Caster is the server infrastructure that receives data from all reference stations and distributes it to clients on request. It maintains a sourcetable — a list of all available correction streams (mountpoints) — and authenticates connecting clients. When you enter an NTRIP host address like ",[461,462,463],"code",{},"ntrip.rtksub.com",", you are connecting to a caster.",[17,466,467],{},"A caster can serve thousands of clients simultaneously from the same set of reference stations. This is why network correction services are economically viable — one physical infrastructure serves many subscribers.",[230,469,471],{"id":470},"ntrip-client-your-device","NTRIP Client — your device",[17,473,474],{},"The NTRIP Client is the software on your side — built into Emlid Flow, SW Maps, Trimble Access, FieldGenius and every other modern field application. It connects to the caster, authenticates, selects a mountpoint and receives the correction stream. The client passes the incoming RTCM3 data to the receiver, which uses it to compute an RTK Fix.",[12,476,478],{"id":477},"how-ntrip-works-step-by-step","How NTRIP works step by step",[480,481,482,489,495,501,507,513],"stepper",{"additionalstyles":34},[483,484,486],"stepper-item",{"title":485},"Reference stations observe satellites",[17,487,488],{},"Permanent GNSS receivers at fixed, precisely surveyed locations track all visible satellites continuously. They measure the difference between what the signals should look like at their known position and what they actually receive — this difference is the correction data.",[483,490,492],{"title":491},"Stations stream RTCM3 to the caster",[17,493,494],{},"Each reference station sends its correction data to the NTRIP caster in real time. The data is formatted as RTCM3 messages — the universal standard for RTK corrections. This stream flows continuously, every second of every day.",[483,496,498],{"title":497},"Your client connects and authenticates",[17,499,500],{},"Your field software (the NTRIP client) opens a TCP connection to the caster on port 2101. It sends an HTTP GET request including your username and password. The caster verifies your credentials and confirms the connection.",[483,502,504],{"title":503},"You select a mountpoint",[17,505,506],{},"The caster sends back a sourcetable listing all available correction streams. You select a mountpoint — the name of the specific correction stream you want. Your client sends the mountpoint name back to the caster, which begins streaming that correction data to you.",[483,508,510],{"title":509},"Corrections flow to your receiver",[17,511,512],{},"The caster streams RTCM3 correction messages continuously to your client. Your field software or NTRIP app passes these to your GNSS receiver — typically via Bluetooth, USB or directly over the network if the receiver has its own IP connection.",[483,514,516],{"title":515},"Your receiver computes RTK Fixed",[17,517,518],{},"The receiver combines the incoming corrections with its own satellite observations. It resolves carrier phase ambiguities — the mathematical step that unlocks centimetre accuracy — and outputs an RTK Fixed position. In good conditions this takes 10–60 seconds from the moment corrections begin flowing.",[63,520,522],{"additionalstyles":34,"color":90,"title":521},"NTRIP is essentially streaming audio — but for position",[17,523,524],{},"A useful analogy: NTRIP works like an internet radio stream. The caster is the radio server. Your NTRIP client is the app on your phone. The mountpoint is the station you tune to. Corrections flow continuously as long as you are connected — and like a radio stream, a brief internet dropout interrupts it until the connection re-establishes.",[12,526,528],{"id":527},"ntrip-vs-radio-link","NTRIP vs radio link",[17,530,531],{},"Before NTRIP became widespread, RTK corrections were delivered by UHF radio — a base station on site broadcast corrections to rovers within line-of-sight range. Radio is still used today, but NTRIP has become the dominant method for most professional applications.",[533,534,538,555,568,581,594,607,620],"compare-table",{"additionalstyles":34,"items":535,"label":536,"winner":537},"UHF radio link|NTRIP","UHF radio link compared with NTRIP","NTRIP",[539,540,542,549],"compare-row",{"title":541},"Range",[543,544,546],"compare-cell",{"status":545},"negative",[17,547,548],{},"2–10 km line of sight. Terrain and buildings block signal.",[543,550,552],{"status":551},"positive",[17,553,554],{},"Unlimited within network coverage. Works across an entire country.",[539,556,558,563],{"title":557},"Infrastructure required",[543,559,560],{"status":545},[17,561,562],{},"Base station, tripod, radio module, battery. 15–30 min setup per job.",[543,564,565],{"status":551},[17,566,567],{},"One rover. Mobile data connection. No base station.",[539,569,571,576],{"title":570},"Works without internet",[543,572,573],{"status":551},[17,574,575],{},"Yes — fully independent of internet or mobile coverage.",[543,577,578],{"status":545},[17,579,580],{},"No — requires mobile data at the rover location.",[539,582,584,589],{"title":583},"Latency",[543,585,586],{"status":551},[17,587,588],{},"\u003C100 ms — very low latency, ideal for machine guidance.",[543,590,591],{"status":551},[17,592,593],{},"\u003C1 s over 4G — acceptable for all surveying applications.",[539,595,597,602],{"title":596},"Number of rovers served",[543,598,599],{"status":545},[17,600,601],{},"Unlimited — radio broadcast reaches all rovers in range.",[543,603,604],{"status":545},[17,605,606],{},"Each rover needs its own NTRIP connection and subscription.",[539,608,610,615],{"title":609},"Accuracy",[543,611,612],{"status":545},[17,613,614],{},"Best within 10 km of base. Degrades at distance.",[543,616,617],{"status":551},[17,618,619],{},"Consistent with VRS across the entire network coverage area.",[539,621,623,628],{"title":622},"Cost",[543,624,625],{"status":545},[17,626,627],{},"High upfront hardware cost. No ongoing fees.",[543,629,630],{"status":551},[17,631,632],{},"Low upfront (one receiver). Monthly subscription for corrections.",[12,634,636],{"id":635},"what-you-need-to-use-ntrip","What you need to use NTRIP",[60,638,639,643,647,651],{"additionalstyles":34},[270,640],{"text":641,"title":642},"Any modern multi-band RTK receiver. Emlid, Trimble, Leica, u-blox ZED-F9P and most others support NTRIP natively.","NTRIP-compatible receiver",[270,644],{"text":645,"title":646},"Built into Emlid Flow, SW Maps, Trimble Access, FieldGenius, Lefebure and most field apps. You are unlikely to need a separate client.","NTRIP client software",[270,648],{"text":649,"title":650},"Mobile data (4G or 3G) at the rover location. A few hundred kilobytes per hour — similar to a basic messaging app.","Internet connection",[270,652],{"text":653,"title":654},"Host address, port (2101), mountpoint name, username and password from your correction service provider.","NTRIP credentials",[63,656,658],{"additionalstyles":34,"color":78,"title":657},"NTRIP data usage is very low",[17,659,660],{},"A typical NTRIP correction stream uses 50–200 KB per hour depending on the mountpoint and number of satellite constellations. Over a full 8-hour working day this is under 2 MB — negligible on any mobile data plan. NTRIP will not meaningfully affect your data allowance.",[12,662,664],{"id":663},"ntrip-v1-vs-ntrip-v2","NTRIP v1 vs NTRIP v2",[17,666,667],{},"There are two versions of the NTRIP standard. Most users will never need to think about this distinction — your software handles it automatically — but it is useful to understand when troubleshooting.",[313,669,670,676],{},[316,671,672,675],{},[21,673,674],{},"NTRIP v1"," (2004) — the original standard. Uses basic HTTP 1.0. One-way communication: the caster sends corrections and receives nothing back from the client. Does not natively support GGA position transmission for VRS. Still widely supported by all servers and clients.",[316,677,678,681],{},[21,679,680],{},"NTRIP v2"," (2007) — adds bidirectional communication over HTTP 1.1. Supports GGA transmission from client to caster within the protocol — this is how VRS mountpoints work. Supports chunked transfer encoding for more reliable streaming. Trimble Access automatically negotiates v2 if the server supports it.",[63,683,685],{"additionalstyles":34,"color":66,"title":684},"Force v1 only if you have connection problems",[17,686,687],{},"Some older equipment or network configurations have problems with NTRIP v2 negotiation. If you cannot connect and everything else looks correct, try forcing your client to use NTRIP v1.0. In Trimble Access this is a checkbox in the survey style data link settings. In most other clients, look for an \"NTRIP version\" dropdown.",{"title":353,"searchDepth":354,"depth":354,"links":689},[690,691,696,697,698,699],{"id":390,"depth":354,"text":391},{"id":417,"depth":354,"text":418,"children":692},[693,694,695],{"id":448,"depth":361,"text":449},{"id":455,"depth":361,"text":456},{"id":470,"depth":361,"text":471},{"id":477,"depth":354,"text":478},{"id":527,"depth":354,"text":528},{"id":635,"depth":354,"text":636},{"id":663,"depth":354,"text":664},"learn\u002Fwhat-is-ntrip.webp","NTRIP is the internet protocol that delivers RTK correction data from reference stations to your rover over a mobile data connection. It replaced radio links as the dominant correction delivery method — and it is the reason a single receiver with a SIM card can achieve centimetre accuracy anywhere in a correction network's coverage area.",{},"2026-07-24",{"title":385,"description":701},"en\u002Flearn\u002Fwhat-is-ntrip","zwxVSM1r0uMgUoqabd-awIyiWlIAORHYhZCmNiesBK0",{"id":708,"title":709,"author":710,"body":711,"category":366,"cover":1095,"description":1096,"extension":369,"meta":1097,"navigation":371,"path":376,"publishedAt":373,"relatedArticles":1098,"seo":1100,"stem":1101,"updatedAt":379,"__hash__":1102},"knowledge_en\u002Fen\u002Flearn\u002Fwhat-is-vrs.md","What is VRS and when do you need it?","Yuri",{"type":9,"value":712,"toc":1086},[713,717,724,727,730,747,751,754,786,792,796,799,869,873,899,903,910,913,919,925,929,932,1004,1008,1011,1080],[12,714,716],{"id":715},"what-vrs-is-and-why-it-exists","What VRS is and why it exists",[17,718,719,720,723],{},"VRS stands for ",[21,721,722],{},"Virtual Reference Station",". It is a network RTK technology that makes your receiver work as if a physical base station were located just beside you, wherever you are within the correction network's coverage area.",[17,725,726],{},"With a normal single-station NTRIP mountpoint, your rover receives corrections from one physical reference station. That station can be 20, 40 or even 60 kilometres away. As the baseline gets longer, the atmospheric conditions at your rover become less like those at the station. Ionospheric and tropospheric errors then make RTK initialisation slower and a Fixed solution less stable.",[17,728,729],{},"VRS solves that problem on the server. It combines observations from several surrounding reference stations, models the conditions at your location and sends a synthetic RTCM correction stream. To your receiver, it looks exactly like corrections from a nearby base station.",[32,731,732,736,740,744],{"additionalstyles":34},[36,733],{"text":734,"title":735},"Typical effective VRS baseline","1–2 km",[36,737],{"text":738,"title":739},"Reference stations used around you","3+",[36,741],{"text":742,"title":743},"Position message required by VRS","GGA",[36,745],{"text":746,"title":39},"Correction format your rover receives",[12,748,750],{"id":749},"how-vrs-works","How VRS works",[17,752,753],{},"VRS is a server-side calculation that runs invisibly behind your NTRIP connection. The sequence is straightforward:",[480,755,756,762,768,774,780],{"additionalstyles":34},[483,757,759],{"title":758},"Connect to a VRS mountpoint",[17,760,761],{},"Your NTRIP client connects to the correction service and sends an NMEA GGA sentence with its approximate position. This two-way communication is what makes VRS different from a normal single-station stream.",[483,763,765],{"title":764},"The server places you in the network",[17,766,767],{},"The VRS server uses your GGA position to identify the physical reference stations around you. It typically selects three or more nearby stations to build the correction model.",[483,769,771],{"title":770},"Atmospheric conditions are modelled",[17,772,773],{},"The server interpolates the ionospheric and tropospheric differences observed across those stations. It estimates the errors that apply at your exact working location.",[483,775,777],{"title":776},"A virtual station is created",[17,778,779],{},"The server synthesises an RTCM3 stream as if a base station existed only a kilometre or two from your rover. No physical hardware is installed at that virtual location.",[483,781,783],{"title":782},"Your receiver computes RTK normally",[17,784,785],{},"Your receiver processes the VRS corrections like any other RTCM3 stream. It does not need to know whether the corrections came from a real or virtual station; it simply benefits from the short effective baseline.",[63,787,789],{"additionalstyles":34,"color":90,"title":788},"VRS changes the effective baseline, not your equipment",[17,790,791],{},"You still use the same rover, field software and NTRIP credentials. Select a VRS mountpoint and transmit GGA; the network does the additional calculation for you.",[12,793,795],{"id":794},"standard-mountpoint-vs-vrs","Standard mountpoint vs VRS",[17,797,798],{},"Both options use the same correction network. The important difference is how the correction stream is made.",[533,800,804,817,830,843,856],{"additionalstyles":34,"items":801,"label":802,"winner":803},"Standard mountpoint|VRS mountpoint","Standard NTRIP and VRS comparison","VRS mountpoint",[539,805,807,812],{"title":806},"Correction source",[543,808,809],{"status":551},[17,810,811],{},"One physical reference station.",[543,813,814],{"status":551},[17,815,816],{},"A virtual station calculated from multiple physical stations.",[539,818,820,825],{"title":819},"Effective baseline",[543,821,822],{"status":545},[17,823,824],{},"The actual distance to the selected station. It may be tens of kilometres.",[543,826,827],{"status":551},[17,828,829],{},"Usually around 1–2 km, even when physical stations are far away.",[539,831,833,838],{"title":832},"GGA transmission",[543,834,835],{"status":551},[17,836,837],{},"Usually not required.",[543,839,840],{"status":545},[17,841,842],{},"Required so the server can generate corrections for your location.",[539,844,846,851],{"title":845},"Working over a large area",[543,847,848],{"status":545},[17,849,850],{},"You may need to change mountpoints as the nearest station changes.",[543,852,853],{"status":551},[17,854,855],{},"The network adapts to your position automatically.",[539,857,859,864],{"title":858},"Fix reliability at long distances",[543,860,861],{"status":545},[17,862,863],{},"Can degrade as atmospheric differences increase.",[543,865,866],{"status":551},[17,867,868],{},"Typically faster to initialise and more stable across the network.",[12,870,872],{"id":871},"when-to-use-vrs-and-when-not-to","When to use VRS — and when not to",[60,874,875,879,883,887,891,895],{"additionalstyles":34},[270,876],{"text":877,"title":878},"Once the nearest physical station is more than roughly 20–30 km away, a VRS stream reduces the baseline-related errors that can keep a receiver in Float or make Fix drop.","Use VRS beyond 20–30 km",[270,880],{"text":881,"title":882},"For work that covers a large area in one day, VRS follows your approximate location. You do not need to keep choosing a different physical station as you travel.","Use VRS when moving across a region",[270,884],{"text":885,"title":886},"If your sky view and connection are good but Fix repeatedly drops on a standard mountpoint, switching to VRS removes baseline length as a likely cause.","Use VRS for unstable Fix",[270,888],{"text":889,"title":890},"High solar activity and geomagnetic disturbances increase ionospheric errors. The network model in a VRS service can compensate for spatial differences much better than a distant single station.","Use VRS during disturbed conditions",[270,892],{"text":893,"title":894},"Within about 15 km of a physical reference station, the atmospheric difference is usually small. A standard mountpoint can work just as well and does not depend on GGA.","A nearby station may be enough",[270,896],{"text":897,"title":898},"The server must receive your GGA position. Without mobile data at the rover, use a local base and radio link or another correction method that works offline.","VRS needs an internet connection",[12,900,902],{"id":901},"the-gga-requirement-explained","The GGA requirement explained",[17,904,905,906,909],{},"VRS has one requirement that a standard NTRIP connection normally does not: your client must send an ",[21,907,908],{},"NMEA GGA sentence"," to the caster. GGA includes latitude, longitude, altitude and fix quality. The server uses it to decide which part of its atmospheric model applies to you and where to place the virtual reference station.",[17,911,912],{},"The position does not need to be centimetre accurate. A Single or Float position is enough to locate you in the correct network area. However, the GGA must contain a valid position before you connect.",[63,914,916],{"additionalstyles":34,"color":66,"title":915},"Connected, but receiving 0 bytes per second? Check GGA first.",[17,917,918],{},"When GGA is disabled, a connection to a VRS mountpoint can look successful but the caster may send no correction data. Your receiver stays on Single and there may be no obvious error message. Enable GGA transmission, then reconnect.",[63,920,922],{"additionalstyles":307,"color":90,"title":921},"Wait for a valid initial position",[17,923,924],{},"Before connecting, give the receiver 30–60 seconds outdoors to obtain satellite lock. A GGA sentence with zero coordinates can be rejected by the server or place the virtual station in the wrong area.",[12,926,928],{"id":927},"how-to-enable-vrs-on-your-device","How to enable VRS on your device",[17,930,931],{},"Select the VRS mountpoint supplied by your correction provider, then make sure GGA transmission is enabled. The wording differs slightly by application.",[933,934,936,951,961,974,984,994],"device-tabs",{"additionalstyles":34,"items":935},"Emlid Flow|Trimble Access|SW Maps|FieldGenius|DJI Pilot|Lefebure NTRIP",[937,938,940],"device-tab",{"name":939},"Emlid Flow",[17,941,942,943,946,947,950],{},"Go to ",[21,944,945],{},"Correction input → NTRIP",". Select your provider's VRS mountpoint, enable ",[21,948,949],{},"Send GGA to caster",", then connect after the receiver has a Single solution.",[937,952,954],{"name":953},"Trimble Access",[17,955,956,957,960],{},"Open ",[21,958,959],{},"Survey Style → Rover radio",", then enter the VRS mountpoint in the NTRIP settings. Trimble Access normally sends GGA automatically while NTRIP is active.",[937,962,964],{"name":963},"SW Maps",[17,965,942,966,969,970,973],{},[21,967,968],{},"Settings → NTRIP Client",", choose the VRS mountpoint from the sourcetable and enable ",[21,971,972],{},"Transmit GGA"," before tapping Connect.",[937,975,977],{"name":976},"FieldGenius",[17,978,979,980,983],{},"Choose ",[21,981,982],{},"Set Up Corrections → RTK via Internet",", add a source with the VRS mountpoint and enable GGA transmission in the data-link settings. Confirm the antenna height, then connect.",[937,985,987],{"name":986},"DJI Pilot",[17,988,989,990,993],{},"In ",[21,991,992],{},"RTK Settings → Custom Network RTK",", enter the VRS mountpoint provided by your service. DJI sends GGA automatically after it has GPS lock, so configure it outdoors.",[937,995,997],{"name":996},"Lefebure NTRIP",[17,998,999,1000,1003],{},"Enter the caster host, port and VRS mountpoint. Enable ",[21,1001,1002],{},"Send GGA"," in the app settings and select your receiver or the phone's internal GPS as the GGA source.",[12,1005,1007],{"id":1006},"vrs-by-another-name","VRS by another name",[17,1009,1010],{},"VRS is the most common name for network RTK, but it is not the only approach. A sourcetable may also contain these alternatives:",[110,1012,1013,1026],{},[113,1014,1015],{},[116,1016,1017,1020,1023],{},[119,1018,1019],{},"Name",[119,1021,1022],{},"What it does",[119,1024,1025],{},"What you need to know",[132,1027,1028,1041,1054,1067],{},[116,1029,1030,1035,1038],{},[137,1031,1032],{},[21,1033,1034],{},"MAC",[137,1036,1037],{},"The caster sends observations from a master station and auxiliary stations; the receiver performs the network calculation.",[137,1039,1040],{},"Common with Leica systems. GGA is not always required.",[116,1042,1043,1048,1051],{},[137,1044,1045],{},[21,1046,1047],{},"FKP",[137,1049,1050],{},"The caster sends area-correction parameters that the receiver applies to a single-station stream.",[137,1052,1053],{},"An older network format that is less common today.",[116,1055,1056,1061,1064],{},[137,1057,1058],{},[21,1059,1060],{},"iMAX",[137,1062,1063],{},"A personalised version of the Master-Auxiliary approach.",[137,1065,1066],{},"Functionally similar to VRS for most users.",[116,1068,1069,1074,1077],{},[137,1070,1071],{},[21,1072,1073],{},"SSR \u002F SSRZ",[137,1075,1076],{},"Separately models satellite orbits, clocks and atmospheric effects.",[137,1078,1079],{},"A newer approach that is becoming more common in modern networks.",[63,1081,1083],{"additionalstyles":34,"color":78,"title":1082},"For most users, choose the VRS mountpoint",[17,1084,1085],{},"Unless your receiver or correction provider specifically asks for MAC, FKP or another format, VRS is the practical default. It works with modern RTK receivers and gives you near-local network corrections throughout the covered area.",{"title":353,"searchDepth":354,"depth":354,"links":1087},[1088,1089,1090,1091,1092,1093,1094],{"id":715,"depth":354,"text":716},{"id":749,"depth":354,"text":750},{"id":794,"depth":354,"text":795},{"id":871,"depth":354,"text":872},{"id":901,"depth":354,"text":902},{"id":927,"depth":354,"text":928},{"id":1006,"depth":354,"text":1007},"learn\u002Fwhat-is-vrs.webp","VRS (Virtual Reference Station) makes a correction network behave as though a base station is right beside your rover. It eliminates long-baseline errors, improves Fix reliability across a network and is simple to use once GGA transmission is enabled.",{},[375,1099],"\u002Fen\u002Flearn\u002Ffloat-vs-fix",{"title":709,"description":1096},"en\u002Flearn\u002Fwhat-is-vrs","Q_R7dGN8SakA5nbtnxs_dK8uAMrv0Wf41kDVzWa369Y",1787304715654]