> For the complete documentation index, see [llms.txt](https://docs.premium-positioning.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.premium-positioning.com/learn/how-to-compare-correction-services.md). # How to compare correction services How to choose an RTK correction service: the five types of service, why distance to the base matters, and four questions that separate services on a bad day. Accuracy is the entry requirement: any survey-grade correction service should deliver centimetre positions in good conditions. The differences between services show on a bad day, when a correction source fails, a result is questioned, or a crew is waiting on a fix. Start by knowing which type of service you are looking at, then compare any service, including RTK Premium, on the four questions below. ### Types of correction service | Type | How it works | What to check | | --------------------------------------- | ----------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- | | Public network | A national or state agency runs reference stations and streams corrections, often free of charge. | Whether an availability commitment is published, who answers when the stream stops, and whether coverage reaches your sites. | | Commercial network RTK | A provider builds the correction for your position from several surrounding stations (network RTK or VRS). | How many correction sources serve your area, the published service level and its remedy, and support hours. | | Crowd-sourced network | Independent owners host single base stations; you connect to the nearest one. | Distance to the nearest base, station uptime, who maintains the stations, and the station's surveyed coordinates. | | Satellite or state-space (PPP-RTK, SSR) | A model of satellite and atmosphere errors is broadcast over the internet or by satellite, without a nearby base. | Convergence time and accuracy. RTK Access, our PPP-RTK service, delivers 3 to 7 cm horizontally. | | Your own base | You set up a receiver on a known point and stream to your rovers. | Survey of the base point, radio or internet range, and the time spent setting up and guarding it. | ### Distance to the base station With a single base, accuracy falls as you move away from it, because the atmosphere over the base differs from the atmosphere over the rover. A common rule of thumb is about 1 mm of extra error per kilometre of baseline, and fixes take longer and drop more often at long range. Network RTK models the atmosphere across the surrounding stations and builds the correction for your position, so accuracy holds more evenly across the coverage area. Ask any provider whether accuracy depends on distance to the nearest base. ### Continuity Does the fix hold when one correction source fails? A service that runs on a single source stops when that source stops. Ask how many correction sources serve your area, and what happens to your connection when one drops. ### Visibility When a fix drops, can you tell whether the problem is your equipment or the network? Ask whether you can see the status of each session yourself, rather than waiting for support to tell you. ### Proof Can you show where a device was, and with what correction, after the fact? Ask whether the service keeps a session record you can show a client or an auditor. ### Accountability Has anyone committed in writing to the service level? Ask whether the availability commitment is published, how it is measured, what the remedy is when it is missed, and how quickly support responds. ### Checklist for any provider * Is the availability commitment published, and what is the remedy when it is missed? * How many correction sources serve your area, and what happens when one fails? * Does accuracy hold across the coverage area, or depend on distance to the nearest base station? * Can you see the status of each session yourself? * Can you produce a session record for any device after the fact? * What is the support response time, and in which hours? Accuracy is the one question you can measure yourself. [Testing a correction service](/learn/testing-a-correction-service.md) shows how to measure any service against a known point at your own sites, and [RTKTEST](/learn/rtktest.md) compares up to three services side by side against a surveyed point. ### How RTK Premium answers | Question | RTK Premium | | -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Continuity | Each Eligible Area is served by redundant correction sources. Under the service level, a minute counts as unavailable only when no source can deliver a valid stream. | | Accuracy | Network RTK: 1 to 2 cm horizontal and sub-3 cm vertical in a fixed solution, with the correction built for your position from the surrounding stations rather than from one base. | | Visibility | The XYZ Platform shows the live status of each session, so you can see whether a device is connected and receiving corrections without waiting for support. | | Proof | The XYZ Platform keeps a session record for each device, which you can show a client or an auditor. | | Accountability | 99.9% monthly availability in Eligible Areas, a refund of the monthly fee on a published scale when a month falls short, and a 2-hour support response in business hours. See [Service level agreement](/service-level-agreement.md). | ### When RTK Premium is not the right fit * A free public network already covers your sites, and a dropped fix costs you little. * You work mainly in areas the coverage map shows as single-source, where RTK Premium runs on a best-effort basis like any single-network service. * Your application needs horizontal position only, which RTK Access is designed for. ### FAQ What is the difference between NTRIP and RTK? RTK is the positioning method: a rover uses corrections from reference stations to reach centimetre accuracy. NTRIP is the protocol that carries those corrections over the internet. See [What is NTRIP](/learn/what-is-ntrip.md). Are free correction networks good enough? For many jobs they are, where a public network covers your sites. Check whether it publishes an availability commitment and who answers when the stream stops. What equipment do I need? You need a GNSS receiver that accepts RTCM 3.x corrections, an internet connection on the receiver or controller, and NTRIP credentials. [Connect a receiver](/set-up-and-connect/connect-a-receiver.md) covers the settings. How far can I be from a base station? With a single base, accuracy and fix reliability fall as the baseline grows. With network RTK, the correction is built for your position, so the question becomes whether your location sits inside the coverage area. Check the [coverage map](https://www.premium-positioning.com/coverage). What is the difference between single-base and network RTK? Single-base RTK uses one reference station, so accuracy depends on your distance to it. Network RTK combines several stations to model errors across the area and build a correction for your position. See [What is network RTK and VRS?](/learn/what-is-network-rtk-and-vrs.md). Is a low-cost NTRIP feed good enough for survey-grade work? It can be on a good day. The questions are what a dropped fix or a disputed result costs you, and whether anyone has committed in writing to the service level. Check the published service level and its remedy before comparing prices. What is the most important thing to check? Check whether the service level is committed in writing, with a remedy when it is missed. Next: [Testing a correction service](/learn/testing-a-correction-service.md). Last updated: 15 October 2026