[{"data":1,"prerenderedAt":1118},["ShallowReactive",2],{"knowledge-page-en-\u002Flearn\u002Fwhat-is-vrs":3},{"article":4,"posts":437,"relatedPosts":438},{"id":5,"title":6,"author":7,"body":8,"category":422,"cover":423,"description":424,"extension":425,"meta":426,"navigation":427,"path":428,"publishedAt":429,"relatedArticles":430,"seo":433,"stem":434,"updatedAt":435,"__hash__":436},"knowledge_en\u002Fen\u002Flearn\u002Fwhat-is-vrs.md","What is VRS and when do you need it?","Yuri",{"type":9,"value":10,"toc":411},"minimark",[11,16,25,28,31,52,56,59,93,101,105,108,183,187,215,219,226,229,236,243,247,250,322,326,329,404],[12,13,15],"h2",{"id":14},"what-vrs-is-and-why-it-exists","What VRS is and why it exists",[17,18,19,20,24],"p",{},"VRS stands for ",[21,22,23],"strong",{},"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.",[17,26,27],{},"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.",[17,29,30],{},"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.",[32,33,35,40,44,48],"text-grid",{"additionalstyles":34},"mt-[60px]",[36,37],"text-grid-item",{"text":38,"title":39},"Typical effective VRS baseline","1–2 km",[36,41],{"text":42,"title":43},"Reference stations used around you","3+",[36,45],{"text":46,"title":47},"Position message required by VRS","GGA",[36,49],{"text":50,"title":51},"Correction format your rover receives","RTCM3",[12,53,55],{"id":54},"how-vrs-works","How VRS works",[17,57,58],{},"VRS is a server-side calculation that runs invisibly behind your NTRIP connection. The sequence is straightforward:",[60,61,62,69,75,81,87],"stepper",{"additionalstyles":34},[63,64,66],"stepper-item",{"title":65},"Connect to a VRS mountpoint",[17,67,68],{},"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.",[63,70,72],{"title":71},"The server places you in the network",[17,73,74],{},"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.",[63,76,78],{"title":77},"Atmospheric conditions are modelled",[17,79,80],{},"The server interpolates the ionospheric and tropospheric differences observed across those stations. It estimates the errors that apply at your exact working location.",[63,82,84],{"title":83},"A virtual station is created",[17,85,86],{},"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.",[63,88,90],{"title":89},"Your receiver computes RTK normally",[17,91,92],{},"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.",[94,95,98],"card",{"additionalstyles":34,"color":96,"title":97},"primary","VRS changes the effective baseline, not your equipment",[17,99,100],{},"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.",[12,102,104],{"id":103},"standard-mountpoint-vs-vrs","Standard mountpoint vs VRS",[17,106,107],{},"Both options use the same correction network. The important difference is how the correction stream is made.",[109,110,114,130,144,157,170],"compare-table",{"additionalstyles":34,"items":111,"label":112,"winner":113},"Standard mountpoint|VRS mountpoint","Standard NTRIP and VRS comparison","VRS mountpoint",[115,116,118,125],"compare-row",{"title":117},"Correction source",[119,120,122],"compare-cell",{"status":121},"positive",[17,123,124],{},"One physical reference station.",[119,126,127],{"status":121},[17,128,129],{},"A virtual station calculated from multiple physical stations.",[115,131,133,139],{"title":132},"Effective baseline",[119,134,136],{"status":135},"negative",[17,137,138],{},"The actual distance to the selected station. It may be tens of kilometres.",[119,140,141],{"status":121},[17,142,143],{},"Usually around 1–2 km, even when physical stations are far away.",[115,145,147,152],{"title":146},"GGA transmission",[119,148,149],{"status":121},[17,150,151],{},"Usually not required.",[119,153,154],{"status":135},[17,155,156],{},"Required so the server can generate corrections for your location.",[115,158,160,165],{"title":159},"Working over a large area",[119,161,162],{"status":135},[17,163,164],{},"You may need to change mountpoints as the nearest station changes.",[119,166,167],{"status":121},[17,168,169],{},"The network adapts to your position automatically.",[115,171,173,178],{"title":172},"Fix reliability at long distances",[119,174,175],{"status":135},[17,176,177],{},"Can degrade as atmospheric differences increase.",[119,179,180],{"status":121},[17,181,182],{},"Typically faster to initialise and more stable across the network.",[12,184,186],{"id":185},"when-to-use-vrs-and-when-not-to","When to use VRS — and when not to",[188,189,190,195,199,203,207,211],"cards",{"additionalstyles":34},[191,192],"cards-item",{"text":193,"title":194},"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",[191,196],{"text":197,"title":198},"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",[191,200],{"text":201,"title":202},"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",[191,204],{"text":205,"title":206},"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",[191,208],{"text":209,"title":210},"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",[191,212],{"text":213,"title":214},"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",[12,216,218],{"id":217},"the-gga-requirement-explained","The GGA requirement explained",[17,220,221,222,225],{},"VRS has one requirement that a standard NTRIP connection normally does not: your client must send an ",[21,223,224],{},"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.",[17,227,228],{},"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.",[94,230,233],{"additionalstyles":34,"color":231,"title":232},"orange","Connected, but receiving 0 bytes per second? Check GGA first.",[17,234,235],{},"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.",[94,237,240],{"additionalstyles":238,"color":96,"title":239},"mt-[30px]","Wait for a valid initial position",[17,241,242],{},"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.",[12,244,246],{"id":245},"how-to-enable-vrs-on-your-device","How to enable VRS on your device",[17,248,249],{},"Select the VRS mountpoint supplied by your correction provider, then make sure GGA transmission is enabled. The wording differs slightly by application.",[251,252,254,269,279,292,302,312],"device-tabs",{"additionalstyles":34,"items":253},"Emlid Flow|Trimble Access|SW Maps|FieldGenius|DJI Pilot|Lefebure NTRIP",[255,256,258],"device-tab",{"name":257},"Emlid Flow",[17,259,260,261,264,265,268],{},"Go to ",[21,262,263],{},"Correction input → NTRIP",". Select your provider's VRS mountpoint, enable ",[21,266,267],{},"Send GGA to caster",", then connect after the receiver has a Single solution.",[255,270,272],{"name":271},"Trimble Access",[17,273,274,275,278],{},"Open ",[21,276,277],{},"Survey Style → Rover radio",", then enter the VRS mountpoint in the NTRIP settings. Trimble Access normally sends GGA automatically while NTRIP is active.",[255,280,282],{"name":281},"SW Maps",[17,283,260,284,287,288,291],{},[21,285,286],{},"Settings → NTRIP Client",", choose the VRS mountpoint from the sourcetable and enable ",[21,289,290],{},"Transmit GGA"," before tapping Connect.",[255,293,295],{"name":294},"FieldGenius",[17,296,297,298,301],{},"Choose ",[21,299,300],{},"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.",[255,303,305],{"name":304},"DJI Pilot",[17,306,307,308,311],{},"In ",[21,309,310],{},"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.",[255,313,315],{"name":314},"Lefebure NTRIP",[17,316,317,318,321],{},"Enter the caster host, port and VRS mountpoint. Enable ",[21,319,320],{},"Send GGA"," in the app settings and select your receiver or the phone's internal GPS as the GGA source.",[12,323,325],{"id":324},"vrs-by-another-name","VRS by another name",[17,327,328],{},"VRS is the most common name for network RTK, but it is not the only approach. A sourcetable may also contain these alternatives:",[330,331,332,348],"table",{},[333,334,335],"thead",{},[336,337,338,342,345],"tr",{},[339,340,341],"th",{},"Name",[339,343,344],{},"What it does",[339,346,347],{},"What you need to know",[349,350,351,365,378,391],"tbody",{},[336,352,353,359,362],{},[354,355,356],"td",{},[21,357,358],{},"MAC",[354,360,361],{},"The caster sends observations from a master station and auxiliary stations; the receiver performs the network calculation.",[354,363,364],{},"Common with Leica systems. GGA is not always required.",[336,366,367,372,375],{},[354,368,369],{},[21,370,371],{},"FKP",[354,373,374],{},"The caster sends area-correction parameters that the receiver applies to a single-station stream.",[354,376,377],{},"An older network format that is less common today.",[336,379,380,385,388],{},[354,381,382],{},[21,383,384],{},"iMAX",[354,386,387],{},"A personalised version of the Master-Auxiliary approach.",[354,389,390],{},"Functionally similar to VRS for most users.",[336,392,393,398,401],{},[354,394,395],{},[21,396,397],{},"SSR \u002F SSRZ",[354,399,400],{},"Separately models satellite orbits, clocks and atmospheric effects.",[354,402,403],{},"A newer approach that is becoming more common in modern networks.",[94,405,408],{"additionalstyles":34,"color":406,"title":407},"green","For most users, choose the VRS mountpoint",[17,409,410],{},"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":412,"searchDepth":413,"depth":413,"links":414},"",2,[415,416,417,418,419,420,421],{"id":14,"depth":413,"text":15},{"id":54,"depth":413,"text":55},{"id":103,"depth":413,"text":104},{"id":185,"depth":413,"text":186},{"id":217,"depth":413,"text":218},{"id":245,"depth":413,"text":246},{"id":324,"depth":413,"text":325},"learn","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.","md",{},true,"\u002Fen\u002Flearn\u002Fwhat-is-vrs","2026-07-25",[431,432],"\u002Fen\u002Flearn\u002Fwhat-is-ntrip","\u002Fen\u002Flearn\u002Ffloat-vs-fix",{"title":6,"description":424},"en\u002Flearn\u002Fwhat-is-vrs",null,"Q_R7dGN8SakA5nbtnxs_dK8uAMrv0Wf41kDVzWa369Y",[],[439,761],{"id":440,"title":441,"author":442,"body":443,"category":422,"cover":754,"description":755,"extension":425,"meta":756,"navigation":427,"path":431,"publishedAt":757,"relatedArticles":435,"seo":758,"stem":759,"updatedAt":435,"__hash__":760},"knowledge_en\u002Fen\u002Flearn\u002Fwhat-is-ntrip.md","What is NTRIP and how does it work?","Wilko",{"type":9,"value":444,"toc":741},[445,449,452,455,472,476,479,503,508,511,515,523,526,530,533,537,575,581,585,588,684,688,706,712,716,719,735],[12,446,448],{"id":447},"what-ntrip-stands-for","What NTRIP stands for",[17,450,451],{},"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.",[17,453,454],{},"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.",[32,456,457,461,465,468],{"additionalstyles":34},[36,458],{"text":459,"title":460},"Standard TCP port","2101",[36,462],{"text":463,"title":464},"Protocol base","HTTP",[36,466],{"text":467,"title":51},"Data format carried",[36,469],{"text":470,"title":471},"Correction latency","\u003C1 s",[12,473,475],{"id":474},"the-three-components","The three components",[17,477,478],{},"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.",[480,481,482,487,491,496,499],"flow-diagram",{"additionalstyles":34},[483,484],"flow-card",{"text":485,"title":486},"NTRIP Server","Reference station",[488,489],"flow-connector",{"text":490},"RTCM3 over internet",[483,492],{"text":493,"title":494,":highlighted":495},"Central hub","NTRIP Caster","true",[488,497],{"text":498},"RTCM3 stream on demand",[483,500],{"text":501,"title":502},"NTRIP Client","Your device",[504,505,507],"h3",{"id":506},"ntrip-server-the-reference-station-side","NTRIP Server — the reference station side",[17,509,510],{},"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.",[504,512,514],{"id":513},"ntrip-caster-the-central-hub","NTRIP Caster — the central hub",[17,516,517,518,522],{},"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 ",[519,520,521],"code",{},"ntrip.rtksub.com",", you are connecting to a caster.",[17,524,525],{},"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.",[504,527,529],{"id":528},"ntrip-client-your-device","NTRIP Client — your device",[17,531,532],{},"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.",[12,534,536],{"id":535},"how-ntrip-works-step-by-step","How NTRIP works step by step",[60,538,539,545,551,557,563,569],{"additionalstyles":34},[63,540,542],{"title":541},"Reference stations observe satellites",[17,543,544],{},"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.",[63,546,548],{"title":547},"Stations stream RTCM3 to the caster",[17,549,550],{},"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.",[63,552,554],{"title":553},"Your client connects and authenticates",[17,555,556],{},"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.",[63,558,560],{"title":559},"You select a mountpoint",[17,561,562],{},"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.",[63,564,566],{"title":565},"Corrections flow to your receiver",[17,567,568],{},"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.",[63,570,572],{"title":571},"Your receiver computes RTK Fixed",[17,573,574],{},"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.",[94,576,578],{"additionalstyles":34,"color":96,"title":577},"NTRIP is essentially streaming audio — but for position",[17,579,580],{},"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.",[12,582,584],{"id":583},"ntrip-vs-radio-link","NTRIP vs radio link",[17,586,587],{},"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.",[109,589,593,606,619,632,645,658,671],{"additionalstyles":34,"items":590,"label":591,"winner":592},"UHF radio link|NTRIP","UHF radio link compared with NTRIP","NTRIP",[115,594,596,601],{"title":595},"Range",[119,597,598],{"status":135},[17,599,600],{},"2–10 km line of sight. Terrain and buildings block signal.",[119,602,603],{"status":121},[17,604,605],{},"Unlimited within network coverage. Works across an entire country.",[115,607,609,614],{"title":608},"Infrastructure required",[119,610,611],{"status":135},[17,612,613],{},"Base station, tripod, radio module, battery. 15–30 min setup per job.",[119,615,616],{"status":121},[17,617,618],{},"One rover. Mobile data connection. No base station.",[115,620,622,627],{"title":621},"Works without internet",[119,623,624],{"status":121},[17,625,626],{},"Yes — fully independent of internet or mobile coverage.",[119,628,629],{"status":135},[17,630,631],{},"No — requires mobile data at the rover location.",[115,633,635,640],{"title":634},"Latency",[119,636,637],{"status":121},[17,638,639],{},"\u003C100 ms — very low latency, ideal for machine guidance.",[119,641,642],{"status":121},[17,643,644],{},"\u003C1 s over 4G — acceptable for all surveying applications.",[115,646,648,653],{"title":647},"Number of rovers served",[119,649,650],{"status":135},[17,651,652],{},"Unlimited — radio broadcast reaches all rovers in range.",[119,654,655],{"status":135},[17,656,657],{},"Each rover needs its own NTRIP connection and subscription.",[115,659,661,666],{"title":660},"Accuracy",[119,662,663],{"status":135},[17,664,665],{},"Best within 10 km of base. Degrades at distance.",[119,667,668],{"status":121},[17,669,670],{},"Consistent with VRS across the entire network coverage area.",[115,672,674,679],{"title":673},"Cost",[119,675,676],{"status":135},[17,677,678],{},"High upfront hardware cost. No ongoing fees.",[119,680,681],{"status":121},[17,682,683],{},"Low upfront (one receiver). Monthly subscription for corrections.",[12,685,687],{"id":686},"what-you-need-to-use-ntrip","What you need to use NTRIP",[188,689,690,694,698,702],{"additionalstyles":34},[191,691],{"text":692,"title":693},"Any modern multi-band RTK receiver. Emlid, Trimble, Leica, u-blox ZED-F9P and most others support NTRIP natively.","NTRIP-compatible receiver",[191,695],{"text":696,"title":697},"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",[191,699],{"text":700,"title":701},"Mobile data (4G or 3G) at the rover location. A few hundred kilobytes per hour — similar to a basic messaging app.","Internet connection",[191,703],{"text":704,"title":705},"Host address, port (2101), mountpoint name, username and password from your correction service provider.","NTRIP credentials",[94,707,709],{"additionalstyles":34,"color":406,"title":708},"NTRIP data usage is very low",[17,710,711],{},"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.",[12,713,715],{"id":714},"ntrip-v1-vs-ntrip-v2","NTRIP v1 vs NTRIP v2",[17,717,718],{},"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.",[720,721,722,729],"ul",{},[723,724,725,728],"li",{},[21,726,727],{},"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.",[723,730,731,734],{},[21,732,733],{},"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.",[94,736,738],{"additionalstyles":34,"color":231,"title":737},"Force v1 only if you have connection problems",[17,739,740],{},"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":412,"searchDepth":413,"depth":413,"links":742},[743,744,750,751,752,753],{"id":447,"depth":413,"text":448},{"id":474,"depth":413,"text":475,"children":745},[746,748,749],{"id":506,"depth":747,"text":507},3,{"id":513,"depth":747,"text":514},{"id":528,"depth":747,"text":529},{"id":535,"depth":413,"text":536},{"id":583,"depth":413,"text":584},{"id":686,"depth":413,"text":687},{"id":714,"depth":413,"text":715},"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":441,"description":755},"en\u002Flearn\u002Fwhat-is-ntrip","zwxVSM1r0uMgUoqabd-awIyiWlIAORHYhZCmNiesBK0",{"id":762,"title":763,"author":442,"body":764,"category":422,"cover":1111,"description":1112,"extension":425,"meta":1113,"navigation":427,"path":432,"publishedAt":757,"relatedArticles":1114,"seo":1115,"stem":1116,"updatedAt":435,"__hash__":1117},"knowledge_en\u002Fen\u002Flearn\u002Ffloat-vs-fix.md","What is the difference between Float and Fix?",{"type":9,"value":765,"toc":1103},[766,770,819,823,826,829,832,863,866,869,873,876,913,917,1048,1052,1055,1081,1085,1088,1091,1097],[12,767,769],{"id":768},"float-vs-fix-at-a-glance","Float vs Fix at a glance",[188,771,772,796],{"additionalstyles":34},[94,773,776],{"additionalstyles":774,"color":231,"title":775},"h-full","Float — Accuracy: 10 cm–1 m horizontal",[720,777,778,781,784,787,790,793],{},[723,779,780],{},"Corrections received but not fully resolved",[723,782,783],{},"Ambiguities treated as real numbers, not integers",[723,785,786],{},"Position jumps of 10–50 cm are normal",[723,788,789],{},"Never adequate for precision survey",[723,791,792],{},"Often a stepping stone toward Fix",[723,794,795],{},"Can look like Fix on some displays",[94,797,799],{"additionalstyles":774,"color":406,"title":798},"Fix — Accuracy: 1–3 cm horizontal, 2–5 cm vertical",[720,800,801,804,807,810,813,816],{},[723,802,803],{},"Carrier phase ambiguities fully resolved to integers",[723,805,806],{},"Position is stable and repeatable",[723,808,809],{},"Centimetre accuracy maintained at speed",[723,811,812],{},"Required for precision survey and stakeout",[723,814,815],{},"Takes 10–60 seconds in good conditions",[723,817,818],{},"Shown in green on most field software",[12,820,822],{"id":821},"what-makes-fix-different-ambiguity-resolution","What makes Fix different — ambiguity resolution",[17,824,825],{},"To understand Float and Fix you need to understand one concept: carrier phase ambiguity. It is the reason RTK can achieve centimetre accuracy at all — and the reason Float cannot.",[17,827,828],{},"GNSS receivers measure position in two ways. The simpler method is pseudorange — measuring the travel time of a satellite signal to estimate distance. Pseudorange gives accuracy of 1–3 metres. The more precise method is carrier phase — measuring the phase of the satellite's radio wave at the receiver antenna. The carrier wave has a wavelength of about 19 cm (for GPS L1). By tracking how many whole wavelengths fit between the satellite and the receiver, and precisely measuring the fractional part, the receiver can measure distance to millimetre precision.",[17,830,831],{},"The problem: the receiver knows the fractional part of the carrier phase precisely, but it does not know how many whole wavelengths there are between it and the satellite. This unknown integer number is called the carrier phase ambiguity — or simply the integer ambiguity.",[109,833,837,850],{"additionalstyles":34,"items":834,"label":835,"winner":836},"Float|Fix","Float and Fix ambiguity comparison","Fix",[115,838,840,845],{"title":839},"Carrier phase ambiguity",[119,841,842],{"status":135},[17,843,844],{},"The integer cycle count is still unknown and treated as a real-valued estimate.",[119,846,847],{"status":121},[17,848,849],{},"The integer cycle count has been confirmed as a specific whole number.",[115,851,853,858],{"title":852},"Position accuracy",[119,854,855],{"status":135},[17,856,857],{},"10 cm–1 m. The fractional phase is measured, but the unresolved cycle count limits accuracy.",[119,859,860],{"status":121},[17,861,862],{},"Centimetre precision. The resolved cycle count unlocks the precise fractional measurement.",[17,864,865],{},"Resolving the integer ambiguity is what RTK does. Using corrections from the reference station — which has its own precisely known position — the rover can cross-check its carrier phase measurements against the reference and mathematically determine the correct integer values. When the receiver is confident it has the right integers for all tracked satellites, it declares RTK Fixed.",[17,867,868],{},"Float means the receiver is still working on this. It has an estimate of the integers — good enough to give sub-metre accuracy — but not yet confident enough to fix them to specific integers. Float accuracy depends on how good the estimate is: anywhere from 10 cm to 1 m, with occasional larger jumps.",[12,870,872],{"id":871},"the-full-solution-progression","The full solution progression",[17,874,875],{},"When you connect to an NTRIP service and power up in the field, your receiver moves through several solution types before reaching Fix.",[60,877,878,885,892,899,906],{"additionalstyles":34},[63,879,882],{"marker":880,"title":881},"—","No fix — Accuracy: none",[17,883,884],{},"The receiver has no satellite lock and no valid position. It is still acquiring signals. This usually takes 15–60 seconds after power-on outdoors.",[63,886,889],{"marker":887,"title":888},"S","Single — Accuracy: 2–5 m",[17,890,891],{},"The receiver has satellite lock and a valid position, but no corrections are applied yet. It uses pseudorange only. This is the type of position reported by standard GPS apps on your phone.",[63,893,896],{"marker":894,"title":895},"D","DGPS \u002F SBAS — Accuracy: 0.3–1 m",[17,897,898],{},"Differential corrections are applied, but only to pseudorange measurements. It is better than Single, but not accurate enough for precision work. This can appear briefly when NTRIP corrections first arrive.",[63,900,903],{"marker":901,"title":902},"FL","Float — Accuracy: 10 cm–1 m",[17,904,905],{},"Carrier phase corrections are applied, but integer ambiguities are not yet resolved. The position is significantly better than Single but not precise enough for survey work. Float is often a transitional state lasting 10–60 seconds before Fix.",[63,907,910],{"marker":908,"title":909},"FX","Fixed — Accuracy: 1–3 cm horizontal, 2–5 cm vertical",[17,911,912],{},"Integer ambiguities are resolved and full RTK accuracy is achieved. This is the solution type required for precision survey, stakeout, machine guidance and drone mapping with ground control points.",[12,914,916],{"id":915},"which-solution-is-good-enough-for-what","Which solution is good enough for what",[109,918,921,937,955,970,986,1001,1017,1032],{"additionalstyles":34,"items":919,"label":920,"winner":836},"Single|Float|Fix","Suitable RTK solution per application",[115,922,924,929,933],{"title":923},"Rough navigation — Finding a plot or general location",[119,925,926],{"status":121},[17,927,928],{},"Good enough",[119,930,931],{"status":121},[17,932,928],{},[119,934,935],{"status":121},[17,936,928],{},[115,938,940,945,950],{"title":939},"Drone mapping — Direct georeferencing without GCPs",[119,941,942],{"status":135},[17,943,944],{},"No",[119,946,947],{"status":135},[17,948,949],{},"Marginal",[119,951,952],{"status":121},[17,953,954],{},"Required",[115,956,958,962,966],{"title":957},"GCP collection for drone mapping",[119,959,960],{"status":135},[17,961,944],{},[119,963,964],{"status":135},[17,965,944],{},[119,967,968],{"status":121},[17,969,954],{},[115,971,973,977,981],{"title":972},"Precision agriculture — Auto-steer with 2–5 cm row guidance",[119,974,975],{"status":135},[17,976,944],{},[119,978,979],{"status":135},[17,980,949],{},[119,982,983],{"status":121},[17,984,985],{},"Preferred",[115,987,989,993,997],{"title":988},"Survey — Topographic surface mapping",[119,990,991],{"status":135},[17,992,944],{},[119,994,995],{"status":135},[17,996,944],{},[119,998,999],{"status":121},[17,1000,954],{},[115,1002,1004,1008,1012],{"title":1003},"Survey — Cadastral or legal property boundaries",[119,1005,1006],{"status":135},[17,1007,944],{},[119,1009,1010],{"status":135},[17,1011,944],{},[119,1013,1014],{"status":121},[17,1015,1016],{},"Required + verification",[115,1018,1020,1024,1028],{"title":1019},"Stakeout to 1 cm",[119,1021,1022],{"status":135},[17,1023,944],{},[119,1025,1026],{"status":135},[17,1027,944],{},[119,1029,1030],{"status":121},[17,1031,954],{},[115,1033,1035,1039,1044],{"title":1034},"Machine control — Earthworks",[119,1036,1037],{"status":135},[17,1038,944],{},[119,1040,1041],{"status":121},[17,1042,1043],{},"Sometimes",[119,1045,1046],{"status":121},[17,1047,954],{},[12,1049,1051],{"id":1050},"how-to-get-from-float-to-fix-faster","How to get from Float to Fix faster",[17,1053,1054],{},"Float is a transitional state. In good conditions it lasts 10–30 seconds. In challenging conditions it can persist indefinitely. These measures help most:",[188,1056,1057,1061,1065,1069,1073,1077],{"additionalstyles":34},[191,1058],{"text":1059,"title":1060},"Ambiguity resolution requires a strong, stable signal from many satellites simultaneously. Even partial canopy cover significantly slows initialisation.","Go outside with a clear sky view",[191,1062],{"text":1063,"title":1064},"The RTK engine converges faster when the antenna is stationary. Once Fixed, you can move normally. Collecting data while still in Float can delay Fix.","Stand still during initialisation",[191,1066],{"text":1067,"title":1068},"Shorter effective baselines make ambiguity resolution faster and more reliable. Beyond 20 km from a physical station, switch to VRS and enable GGA.","Use a VRS mountpoint",[191,1070],{"text":1071,"title":1072},"More satellites provide more measurement redundancy. Adding GLONASS, Galileo and BeiDou can halve Float-to-Fix time compared with GPS-only.","Enable all satellite constellations",[191,1074],{"text":1075,"title":1076},"Verify that bytes per second is non-zero. A dropped and reconnected correction stream resets initialisation and can leave the receiver stuck on Float.","Check the NTRIP connection",[191,1078],{"text":1079,"title":1080},"Above 4, satellite geometry is poor and ambiguity resolution may not converge. Wait for the geometry window to improve, typically within 15–30 minutes.","Check PDOP",[12,1082,1084],{"id":1083},"false-fix-the-hidden-danger","False Fix — the hidden danger",[17,1086,1087],{},"The most dangerous scenario in RTK is a false Fix — the receiver declares Fixed but has resolved the ambiguities to the wrong integers. The position looks centimetre-precise and stable, but it is wrong by one or more carrier wavelengths (19 cm per L1 cycle).",[17,1089,1090],{},"False Fix produces errors of exactly one or more multiples of the carrier wavelength — 19 cm, 38 cm, 57 cm and so on. It is more common at long baselines, in high multipath environments and during solar storms when ionospheric noise is high.",[94,1092,1094],{"additionalstyles":34,"color":231,"title":1093},"How to detect a false Fix",[17,1095,1096],{},"Always verify on a known control point at the start of any precision survey. Set up over a point with published coordinates and compare your measured position with the known values. A discrepancy of exactly around 19 cm, 38 cm or 57 cm in any direction strongly indicates a false Fix. Disconnect, move to open sky, reconnect and re-initialise before continuing.",[94,1098,1100],{"additionalstyles":34,"color":96,"title":1099},"Fix quality indicator — ratio",[17,1101,1102],{},"Many receivers and field software applications report a Fix quality ratio alongside the solution type. A ratio above 3.0 indicates high confidence. A ratio between 1.5 and 3.0 means the Fix is tentative, so verify it on known points. A ratio below 1.5 may indicate that the receiver should not have declared Fix at all.",{"title":412,"searchDepth":413,"depth":413,"links":1104},[1105,1106,1107,1108,1109,1110],{"id":768,"depth":413,"text":769},{"id":821,"depth":413,"text":822},{"id":871,"depth":413,"text":872},{"id":915,"depth":413,"text":916},{"id":1050,"depth":413,"text":1051},{"id":1083,"depth":413,"text":1084},"learn\u002Ffloat-vs-fix.webp","Float and Fix are the two RTK solution types. They look similar on a status screen — both show a position with corrections applied — but the accuracy difference between them is enormous. Fix is centimetres. Float is decimetres to metres. Never collect survey data at Float.",{},[431],{"title":763,"description":1112},"en\u002Flearn\u002Ffloat-vs-fix","rVrcpStYIvAqW_8pcTB5DaAOMLXiCzzea9VNPOocA4Y",1787304609933]