GPS, GNSS and RTK describe different parts of satellite positioning. GPS is one satellite navigation system. GNSS is the broader term for global navigation satellite systems. RTK is a positioning technique that uses suitable measurements and correction data to improve accuracy.
For a drone buyer, these are not three interchangeable product categories. A module can receive signals from multiple GNSS constellations and also support RTK. The practical choice depends on your positioning requirement and the complete installation.
## GPS and GNSS: the terminology
GPS stands for Global Positioning System, the United States' satellite navigation system. It is one example of a GNSS, as explained by the [EU Agency for the Space Programme](https://www.euspa.europa.eu/eu-space-programme/egnos/faqs/what-difference-between-gps-and-egnos).
Product listings sometimes use “GPS module” as a familiar category label. Read the actual specification to see which constellations, signals and functions the receiver supports. A name on the category page is less precise than the documentation for the specific model.
## What RTK adds
Real-Time Kinematic positioning uses correction information from a reference source together with the receiver's satellite measurements. Suitable RTK systems can provide centimeter-level positioning under appropriate conditions; that does not make the same accuracy automatic for every installation or location.
In a local-base arrangement, a reference receiver supplies corrections to the rover receiver on the aircraft. Network-based corrections can be another option. See [u-blox's explanation of RTK and GNSS corrections](https://www.u-blox.com/en/technologies/rtk-real-time-kinematic) for the underlying distinction.
## Define what you need before buying an RTK module
Write the requirement in terms of the task. Do you need position information for general navigation, more repeatable positioning for a defined workflow, or position data for a mapping deliverable?
Separate the receiver's positioning specification from the accuracy of the finished job. For mapping, an aircraft position estimate alone does not establish the accuracy of the final map; the capture and processing workflow must also be assessed.
Turn that requirement into an acceptance question: what will be measured, under what conditions, and against which reference? This is more useful than asking only whether a product is “high precision.”
## Plan how corrections will reach the aircraft
If you choose RTK, identify the correction source and delivery path before ordering. A local-base setup needs the appropriate ground-side equipment and a working path to the rover. Holybro's [H-RTK setup guide](https://docs.holybro.com/gps-and-rtk-system/zed-f9p-h-rtk-series/setup-and-getting-started-px4) illustrates one arrangement involving base and rover units, ground software and telemetry.
For a network service, confirm coverage, access requirements, supported data and the internet connection used by the setup. NTRIP is a protocol used to stream GNSS correction data over the internet; it is not a satellite constellation or a guarantee of receiver compatibility. See [u-blox's NTRIP overview](https://www.u-blox.com/en/technologies/what-is-ntrip).
Ask how the installed system reports its positioning status and how the aircraft is configured to respond when required positioning quality is unavailable. Do not assume that merely receiving some correction data confirms the required result.
## Check integration beyond the receiver chip
Compare the exact module's interface, cable pinout, supply requirements, antenna arrangement and mounting guidance with your flight controller. Then verify support in the firmware release you intend to use.
RTK positioning, heading output and post-processing support are distinct capabilities. PX4's [RTK GNSS documentation](https://docs.px4.io/main/en/gps_compass/rtk_gps) distinguishes these features across devices. Buying an RTK-capable receiver does not establish that every one of those functions is available in your configuration.
## A navigation-module request checklist
- Aircraft and flight controller model, plus intended firmware release.
- Positioning task and a measurable acceptance requirement.
- Module interface, antenna and installation constraints.
- Correction source and delivery path, if RTK is required.
- Required heading or recording functions, specified separately.
- Receiver, cables, mounts and any ground-side items included in the quote.
Browse **GPS & GNSS Modules** together with **Flight Controllers** using this checklist. Identify the entire navigation configuration before comparing its purchase cost.
## Frequently asked questions
### Does every GNSS module support RTK?
No. Check explicit RTK support, the supported correction data and the documented integration method for the model.
### Do I always need to own a local base station?
No. A compatible network correction service may be an option where coverage and connectivity suit the project. Confirm the complete setup and any ongoing access costs.
### Will RTK always produce centimeter-level results?
No. Results depend on the equipment, correction source, installation, satellite reception and operating conditions. Verify performance against the requirement for your own project.
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