What Is PPK (Post-Processed Kinematic)?

First, let’s define PPK. The term stands for Post-Processed Kinematic—a positioning method in which corrections are applied after data collection, unlike RTK, which applies them in real time.

In practice, the rover (e.g., a surveying instrument or drone) records its raw GNSS observations in the field. Later, those logs are matched with observation data from a reference (base) station to compute the precise position. In drone mapping, for example, each aerial photo is tagged with the drone’s GPS coordinates as recorded during flight; once the drone returns, its log is processed together with the base-station data, yielding centimetre-level accuracy—without any real-time link while airborne.

If RTK “solves the problem on the spot,” PPK “brings the data home for careful calculation.”

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PPK Positioning Workflow and Data-Processing Steps

In PPK, at least two GNSS receivers are involved—a base station and a rover. While the rover (e.g., a drone-mounted unit or survey pole) is in operation, it logs raw satellite measurements every second. At the same time—but without any live link—the base receiver, installed at a known location (or drawn from a CORS network), records its own raw data. No real-time communication between the two receivers is required.

After the mission, you bring both data sets into dedicated software or a cloud service for post-processing. The program pairs each rover epoch with the matching base epoch and subtracts the common error terms in the satellite ranges, reconstructing the rover’s trajectory with centimetre-level accuracy. A position that may have been off by tens of centimetres in the field can thus be refined to within a few centimetres. For example, when you PPK-correct the geotags of aerial photos, each image is assigned an accurate coordinate in a public reference frame, ready to be dropped precisely onto maps or CAD drawings.

In short, the workflow is (1)Field collection: the rover and base station each record their own GNSS data.→ (2) Office/cloud processing: the two data sets are merged, corrected, and the positions are computed.→ (3) Output: the corrected, high-precision coordinates are exported as the final deliverable.

PPK sacrifices real-time feedback, but it compensates with consistently high accuracy.

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Differences Between PPK and RTK—and When to Use Each

Now that we understand PPK, let’s contrast it with RTK. We’ll compare the two in terms of real-time capability, communication requirements, accuracy, and operating cost, and then highlight how to choose the right method for a given field scenario.

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Balancing Real-Time Needs and Accuracy

The key difference between RTK and PPK is when corrections are applied. RTK applies them on the fly, delivering high-precision positions immediately while you work. This is ideal when you need to use the data on site without delay—for example, guiding construction machinery in real time or checking survey results instantly.

By contrast, PPK applies the corrections only after data collection, so while you are in the field you have only approximate positions; the precise coordinates are revealed later in the office. The upside is that offline processing can maximise data integrity and accuracy: transient satellite dropouts or radio interruptions that might occur during real-time work can be bridged in post-processing, often yielding accuracy equal to—or even better than—RTK. In other words, you trade RTK’s immediacy for PPK’s reliability.

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Impact of the Communication Environment — Why PPK Excels Where Signals Don’t Reach

RTK requires a live data link from the base station to the rover. That link—whether a dedicated radio or a mobile-network connection (NTRIP, for example)—is highly sensitive to range and signal quality. In forests, mountains, or dense urban canyons, radio waves can be blocked or reflected, making the connection unstable. For drones, antenna orientation changes as the aircraft maneuvers, so the link may drop when the drone turns or passes behind an obstacle. In RTK, any loss of communication can immediately degrade accuracy or even halt positioning altogether.

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Conceptual diagram of RTK (Real-Time Kinematic):
The base station (lower left) and the rover—here, a drone (upper right)—remain connected by a live data link (arrow at the bottom of the figure) throughout the survey. Correction data are transmitted continuously, and the method delivers its full benefits only while the link stays reliable—typically within a range of a few kilometres.

PPK, by contrast, requires no live communication link in the field.

Because the rover and base simply log data independently, you can bring back positioning records from deep mountain valleys or underground spaces—as long as the GNSS signal itself is available. Say you are surveying or inspecting a long stretch of railway or highway: parts of the route may pass through tunnels or remote areas with no coverage, yet PPK still lets you capture continuous, centimetre-level positioning data along the entire section. In fact, PPK is regarded as the method of choice for wide-area surveys and for sites where the communication environment is unstable or nonexistent. Since the corrections are applied later, you never have to worry about real-time link failures while you are measuring.

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Cost and operational differences
From an operational standpoint, the equipment and expenses vary depending on whether you use real-time processing or post-processing. Running RTK requires dedicated base-station hardware and communications gear.If you install your own base station, you must purchase a high-precision GNSS receiver and a radio transceiver; even if you rely on a public CORS or a commercial network-RTK service, you still incur the cost of communication hardware and subscription fees.In short, RTK’s operating cost is the sum of the up-front investment required to obtain instant results on site plus the ongoing expense of maintaining the communication link.

By contrast, PPK requires no communications infrastructure, which simplifies the hardware setup. You still need a high-precision base receiver, but no real-time radio or modem; in fact, you can often use RINEX log files from an existing CORS station obtained after the survey to generate the necessary corrections.

This means you save on communication costs, but you incur expenses and labour for data processing. You may need dedicated PPK software (such as DJI Terra, Pix4D, or RTKLIB) or a cloud-processing service, and the licence fees or staff time for these become the main cost factors.

Operational workflows differ as well. With RTK, you obtain results right in the field, so no downstream data-processing step is needed—an immediate benefit on labor-constrained sites. PPK, by contrast, requires office work after the survey; it suits projects that prioritize ultimate accuracy or must cope with poor communications rather than speed. That said, new cloud platforms now automate PPK workflows, so the overhead is much lower than it once was. For example, some services let you simply upload drone-survey data and the cloud handles both PPK correction and orthophoto generation automatically.

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Key takeaways for choosing the right method
RTK excels in scenarios that demand centimeter-level accuracy in the moment—for example, construction-site management, precision agriculture, and autonomous-driving systems.PPK, by contrast, is ideal for applications where dependable accuracy without live communications is paramount—such as drone aerial mapping, forest surveys, or long-distance infrastructure inspections. Weigh the strengths and weaknesses of each method and choose the approach that best fits your specific use case and field conditions.

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PPK Use Cases in Construction and Surveying

Let’s look at how PPK is applied in real-world projects across the construction and surveying sectors. From drone-based aerial mapping to civil-engineering site management and railway or highway inspections, the following examples illustrate where PPK’s strengths truly shine.

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Applying PPK in Drone Surveying

In recent years, aerial photogrammetry with drones (UAVs) has become widespread. Traditionally, surveyors had to lay out many ground-control points (GCPs) to georeference each photo, but the arrival of RTK/PPK-equipped drones has boosted efficiency dramatically. Among these, PPK-based drone surveying is drawing special attention because it lets you map large areas with high accuracy.

For example, when surveying forests or mountainous areas, drones can capture large swaths from above, yet there is often no ground-based communications infrastructure. A PPK-enabled drone handles this effortlessly: it records position logs autonomously during the flight and, once back on the ground, merges them with base-station data to produce centimetre-accurate orthophotos and point-cloud models. Because it delivers a few-centimetre precision even outside radio coverage, PPK is now used for forest inventories and the measurement of steep cut-and-fill slopes.

Many manufacturers now offer RTK/PPK-ready platforms; DJI’s Phantom 4 RTK, for instance, lets you toggle between RTK and PPK modes. In areas where the RTK link cannot reach, you simply log in PPK mode and apply precise corrections later, ensuring you always have the optimal workflow. Photogrammetry packages such as Pix4D and Agisoft Metashape can process either RTK or PPK data, enabling high-quality 3-D models from the centimetre-level imagery captured in PPK flights.

Impact: Using PPK in drone surveys allows you to slash the number of ground-control points (GCPs) while still maintaining accuracy. On slope-face flights, for instance, safety considerations favor minimizing targets—yet PPK delivers sufficient positional precision with only a few markers. The result is lighter field workload and high-quality terrain data, ideal for volume calculations and ongoing monitoring of earth-surface changes.

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Error-Correction in Civil-Engineering Site Management

PPK also serves as an error-correction tool in civil-engineering projects. On roadworks or land-development sites, crews must measure large numbers of points with machines or survey instruments. Under normal conditions they check as-builts—fill heights, gradients, and so on—using RTK in real time, but in mountain valleys or underground works a live correction link is often impossible. In such cases, you can post-process the logged measurements with PPK to recover centimetre-level accuracy afterwards.

In practice, you save the GPS logs recorded by the machines—or the point coordinates surveyed after the work—and later run PPK against the corresponding base-station data. Positions that were only roughly accurate in real time are refined to centimetre-level precision during post-processing, making them suitable for as-built checks and quantity calculations. This lets crews press ahead quickly on site while still upgrading the recorded data later, so the corrected coordinates can be reflected in inspection reports and construction drawings.

In modern construction ICT, point-cloud data captured by drones and terrestrial laser scanners are increasingly used for site management. By assigning public-grid coordinates to each cloud with PPK, you can align point clouds collected at different times or with different sensors to centimetre-level accuracy.

That alignment enables advanced analyses—such as comparing pre- and post-construction terrain to calculate volumes, or overlaying the design model with the as-built cloud to evaluate workmanship. As an error-correction technique, PPK thus underpins quality assurance throughout the construction PDCA cycle.

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PPK in Railway and Highway Infrastructure Inspections

PPK also plays a key role in maintaining long linear infrastructure such as railways and expressways. Inspectors must collect data along the full length of track or roadway—but communication coverage is rarely perfect along the entire route. Tunnels, mountain sections, and areas beneath elevated structures can block even GNSS signals.

To cope with this, mobile inspection platforms now incorporate PPK. A rail-inspection trolley or highway patrol vehicle, for example, carries a high-precision GNSS receiver and logs its position continuously while it moves. Even through mountain stretches where real-time corrections are impossible, the system keeps recording. After the run, all data are processed together with base-station logs in a single PPK session, yielding a continuous, centimetre-accurate coordinate stream for the entire corridor. That unified accuracy allows rail-warp measurements, pavement-roughness detection, and similar assessments to be performed without positional drift from start to finish.

PPK is equally valuable for drone-based infrastructure inspections. When surveying transmission lines, bridges, or highway viaduct piers from the air, it can be difficult to maintain an RTK correction link. In areas with poor radio coverage, operators often switch the aircraft to a “log-only” mode, focusing on recording data for later PPK processing instead of relying on real-time RTK. After the flight, the imagery is geotagged with PPK-refined coordinates, so any defects captured during the inspection can be plotted precisely on a map. In fact, PPK has proven particularly effective for inspecting power lines and pipelines, helping to increase the reliability of inspection workflows.

PPK is also being used to assess infrastructure damage after earthquakes and other disasters. In such events the communications network is often down, yet inspectors can survey damaged railway structures with PPK-capable GNSS equipment and later calculate precise deformation during post-processing. Whenever rock-solid accuracy takes precedence over immediacy—particularly in critical infrastructure diagnostics—PPK is an invaluable tool.

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LRTK — A Dual-Mode Solution and Its Benefits

Finally, let’s look at LRTK, a positioning system that can handle both RTK and PPK workflows. Developed by Lefixea Inc., LRTK is a palm-sized GNSS receiver that turns a smartphone or tablet into an “all-purpose survey instrument.” It is designed so that field surveyors and engineers can access centimetre-level accuracy with minimal effort—whether they need real-time RTK fixes or post-processed PPK solutions.

The standout feature of LRTK is its ability to switch positioning modes to match the communication environment. Under normal conditions it operates as a network-RTK rover, pulling corrections via Ntrip over a mobile-data link and delivering centimetre-level accuracy on the spot. For sites with no cellular coverage, an optional antenna lets the unit receive Japan’s Quasi-Zenith Satellite “Michibiki” CLAS signal (Centimeter-Level Augmentation Service), so high-precision positioning remains available even in remote mountain areas or underground works.

This means the device can still achieve centimetre-level accuracy in mountains or underground—locations where no cellular signal is available—by using the satellite-borne augmentation signal instead. In effect, LRTK lets you switch seamlessly between real-time RTK and offline positioning, making it easy to run a PPK-style workflow (log in the field, process later).

LRTK also ties into LRTK Cloud, where all captured positions and photos are stored and managed. Field crews can upload geo-tagged images directly from site, streamlining office-side post-processing and report creation. On one infrastructure-inspection project, for example, cracks photographed with an LRTK-equipped phone were instantly tagged with precise coordinates and plotted on a cloud map, enabling rapid information sharing among stakeholders and faster repair responses.

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Key Benefits of Introducing LRTK

• Flexibility: RTK and PPK in one device
  Switch between real-time corrections and post-processing, depending on connectivity, and keep centimetre-level accuracy under any conditions.

• Portability and ease of use
  The compact module snaps onto a smartphone, enabling one-hand operation in the field with no complicated setup.

• High precision at low cost
  Replaces expensive base stations and survey instruments with a lightweight device; Japan’s free QZSS CLAS signal further reduces running costs.

• Cloud integration for greater efficiency
  Position data and site photos are uploaded and managed in LRTK Cloud, streamlining post-processing, sharing, and office-field coordination.

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In short, LRTK is a hybrid positioning solution that blends RTK’s immediacy with PPK’s reliability. It can become a powerful tool not only for general contractors and surveying firms but also for engineers responsible for infrastructure maintenance and inspections.