PPK setups overview
PPK (Post-Processed Kinematic) is a GNSS positioning technique that delivers centimeter-level accuracy by processing satellite observations after the survey is completed.
Like RTK, PPK uses two receivers:
- a stationary base station,
- a moving rover.
The base station records raw satellite observations at a known location, while the rover records observations as it moves through the survey area. After the fieldwork is complete, the observations from both receivers are combined during post-processing to calculate accurate rover positions.
Unlike RTK, PPK does not require a real-time communication link between the base and rover. This makes it particularly useful in areas with poor cellular coverage, unreliable radio communication, or environments where maintaining a continuous correction link is difficult.
Depending on your survey workflow and the result you need, you can process GNSS data in several ways:
- Kinematic processing: Calculate a precise rover trajectory from raw GNSS data recorded by the base and rover without a real-time correction link.
- PPK drone mapping: Calculate precise positions for images captured during a drone flight and geotag them for further processing in photogrammetry software.
- RTK drone mapping: Recover accurate geotags for an RTK-capable drone by post-processing its logged raw GNSS data together with a local Reach base, when RTK corrections were lost or degraded during the flight.
- Stop & Go with Emlid Flow: Improve the coordinates of points collected in Emlid Flow without a real-time correction link by post-processing the recorded GNSS data.
The section below explains each workflow and when to use it.
To process the collected data, you need post-processing software. Emlid Studio is our free desktop application for post-processing GNSS data from GNSS receivers and PPK/RTK drones. It is available for Windows and macOS and supports all the workflows described in this guide.
| Windows (v10 64-bit and later) | macOS (v10.14 and later) |
|---|---|
| Get Emlid Studio | Get Emlid Studio |
To learn more about PPK positioning, check out our blog article:
Learn how PPK works and how it delivers centimeter-level accuracy without a real-time correction link.
PPK setups
The PPK setup depends on what you survey and what equipment you use. Below are the most common field scenarios:
Kinematic processing
With Kinematic processing, you record raw GNSS data on the base and rover and calculate a precise rover trajectory during post-processing in Emlid Studio. Because the workflow does not require a real-time correction link, it is useful when radio communication is unreliable or an NTRIP connection is unavailable due to limited internet access.
Kinematic processing can also serve as a backup for an RTK survey. By logging raw data on both the base and rover during fieldwork, you can post-process the data later if real-time corrections are interrupted or unavailable.
Learn how to record PPK logs, then process the data with the Kinematic processing workflow in Emlid Studio.
PPK drone mapping
A Reach M2 or M+ module on the drone records raw GNSS observations and timestamps each photo. A local Reach base records logs simultaneously. After the flight, Emlid Studio calculates precise positions for each photo and embeds them into the image EXIF data.
Learn how to configure Reach for mapping, then process the logs with the Drone data processing workflow in Emlid Studio.
RTK drone mapping
In this setup, a Reach receiver operates as a local base station while an RTK-capable drone performs the flight. Both the base and drone record raw GNSS data, and the drone also saves an MRK file with image event information. If RTK corrections are lost or degraded during the flight, you can post-process the recorded data in Emlid Studio to calculate precise positions and recover accurate geotags for the captured images.
Learn how to record PPK logs on your Reach base, then process the data with the RTK drone data processing workflow in Emlid Studio.
Stop & Go with Emlid Flow
In this setup, one Reach receiver operates as a base, while another is used as a rover to collect individual points in Emlid Flow. The rover operator pauses briefly at each point while both receivers record raw GNSS data.
After the survey, Emlid Studio combines the base and rover logs with the CSV file exported from Emlid Flow to calculate precise coordinates for the collected points. This workflow is useful for control point surveys, asset mapping, and other ground surveys where real-time corrections are unavailable or not required.
Learn how to record Stop & Go logs, then process the data with the Stop & Go with Emlid Flow workflow in Emlid Studio.
PPK workflow basics
Before starting a PPK survey, consider the following requirements:
Satellite visibility
Both the base and rover need a clear view of the sky throughout the survey. Obstructions such as buildings, trees, cliffs, and heavy canopy can block satellite signals and reduce positioning accuracy. Since PPK relies entirely on recorded satellite observations, maintaining good satellite visibility during data collection is essential for successful post-processing.
Base station setup
The base station must remain stationary and record raw GNSS observations continuously throughout the survey session. Base coordinates for processing can be obtained in one of two ways:
- by placing the base over a known control point, or
- by post-processing one or more observation logs from the nearest CORS station.
PPK can accurately determine the positions of surveyed points relative to each other, but their absolute position depends on the accuracy of the base coordinates. An incorrect base position can therefore shift the entire dataset without affecting the relative accuracy between points. You can correct this later by reprocessing the data in Emlid Studio with the correct base coordinates. Alternatively, apply the corresponding shift to the exported dataset in your CAD or GIS software.
Observation overlap
For successful post-processing, the base and rover must record data during overlapping time periods. The base should begin logging before the rover starts collecting data and continue recording until after the rover finishes. Insufficient overlap between base and rover observations can prevent successful processing or reduce solution quality.
Baseline length
The distance between the base and rover, known as the baseline, affects processing accuracy. PPK assumes that the base and rover experience similar atmospheric conditions. As the distance between them increases, atmospheric differences become more significant and can introduce positioning errors. For best results, keep the baseline as short as possible. While longer baselines are supported, shorter distances generally provide more reliable and accurate solutions.
Coordinate system
The base station determines the coordinate system used by the entire PPK setup. All rover measurements are calculated in that same coordinate system. If the base station is defined in a different coordinate system than the one required for your project, every measured point will be shifted by the same horizontal and vertical offset.
Before processing your survey data, verify that:
- the base coordinates are defined in the correct coordinate system,
- the project uses the correct coordinate system when using the Stop & Go workflow,
- the output coordinate system in Emlid Studio matches the project coordinate system. By default, Emlid Studio uses the datum from the RINEX header, so make sure to change it if it doesn't match your project.
Verifying these settings before processing helps prevent systematic positioning errors and ensures the resulting coordinates align with the rest of the project data.