What is a positioning photo? Benefits of photos with high-precision location information realized by LRTK

Table of contents

• What is a positioning photo?

• Limitations of conventional geotagged photos

• Emergence of high-precision positioning technology (RTK)

• Turning a smartphone into a positioning camera with LRTK

• Benefits of photos with high-precision location information

• Use cases for positioning photos

• Simple surveying with LRTK

• Frequently asked questions

What is a positioning photo?

In recent years, it has become common to attach location information (geotags) to photos taken with smartphones or digital cameras. SNS and photo apps often offer the ability to display photos on a map as the “shooting location.” However, did you know that such ordinary geotagged photos have limits in terms of the accuracy of their location data? Position information from a typical smartphone GPS can have errors on the order of several meters to several tens of meters. As a result, there are many cases where the location recorded in a photo cannot be precisely identified.

Introduced to solve these problems is the “positioning photo.” A positioning photo is a photo that records the shooting location’s high-precision coordinates along with the image. In short, it is a photo with position information added at centimeter-level accuracy (cm level accuracy (half-inch accuracy)). “Positioning” refers to measuring location, a term used in the field of satellite positioning (GNSS); a positioning photo therefore means a photo whose shooting location has been accurately identified using advanced positioning techniques.

In a positioning photo, the photo data is tagged with the shooting point’s latitude and longitude (and altitude if needed) with high precision. In addition, the orientation (direction) at the time of shooting can be recorded, so you can know which way the photo was taken. This makes it possible to tell “where” and “which direction” a photo was taken just by looking at it. While a standard geotagged photo indicates “roughly around here,” a positioning photo can pinpoint a location on a map or drawing within an error range of a few centimeters (a few in). This high level of accuracy is extremely important when using photos for field records or surveying.

Thus, a positioning photo can be described as a fusion of photography and surveying. Because it allows you to record situations with a camera while simultaneously acquiring accurate positioning data, it achieves efficiency and accuracy that were previously unattainable.

Limitations of conventional geotagged photos

With ordinary GPS-based location recording, errors tend to grow particularly large in dense urban areas or mountainous regions. For example, even if you photograph a loose bolt on a bridge during infrastructure inspection, the location information from a conventional photo may only vaguely indicate “somewhere near the center of the bridge.” Also, photo data often does not include altitude information, or the altitude accuracy is low, making it difficult to grasp three-dimensional spatial relationships. Even if you later try to find that bolt precisely, it can be time-consuming to locate it using only the photo. When you want to place multiple photos on a map for management, misaligned locations for each photo prevent accurate placement and undermine the reliability of the records.

To ensure reliable field data, it used to be necessary to measure coordinates separately with surveying equipment or GNSS receivers and then match those coordinates to photos afterward. Conventional methods required manual notes and alignment, which took time and were prone to errors. In this way, ordinary geotagged photos had limitations both in accuracy and work efficiency, and a better solution was needed.

Emergence of high-precision positioning technology (RTK)

To add accurate location information to photos, the accuracy of the position measurement itself must be improved. The key to this is the high-precision positioning technology that has become widespread in recent years. The representative example is the positioning method called RTK. RTK (Real Time Kinematic) is a technique in which a reference receiver and a rover receiver simultaneously receive GNSS satellites and correct relative errors with respect to the reference point to achieve centimeter-level accuracy.

Real-time centimeter-level positioning, which previously required expensive surveying equipment, has become more accessible thanks to RTK. In recent years, GNSS receivers have become smaller and less expensive, making high-precision positioning increasingly familiar. In Japan, the distribution of correction information via electronic reference station networks and the provision of centimeter-level augmentation services (CLAS) by the quasi-zenith satellite “Michibiki” are advancing, and environments are being established where anyone can use high-precision positioning via internet connections or satellite information. Thanks to these technological foundations, combining photography with high-precision position acquisition has become practically feasible.

Turning a smartphone into a positioning camera with LRTK

So how is a positioning photo actually realized? One answer is the solution “LRTK,” which combines a smartphone with high-precision GNSS. LRTK is a compact RTK-GNSS receiver that can be attached to a smartphone, and when paired with a dedicated app it transforms the smartphone into a camera capable of high-precision positioning. By attaching a compact device that contains a battery and antenna to a smartphone and launching the app, you can start centimeter-level positioning immediately without complicated setup.

With LRTK, when you take a photo you simultaneously acquire precise coordinates of the shooting location, and those coordinates are linked to and saved with the photo data. By using the smartphone’s electronic compass, the shooting direction (bearing) can also be recorded. This allows you to obtain high-precision geotagged photos simply by pressing the shutter in the field, eliminating the need to measure coordinates separately later. The acquired photos and position data can be synced to the cloud with one button, enabling real-time confirmation of field photos and their exact positions from the office. LRTK supports not only network RTK via internet communication but also Japan’s satellite augmentation signal (Michibiki’s CLAS), so high-precision positioning can be performed even in mountainous areas or remote islands outside mobile coverage. In short, as long as you have a smartphone, anyone can take positioning photos anywhere.

Benefits of photos with high-precision location information

The benefits that high-precision location-tagged photos bring to the field are immense. Here are some main advantages.

• Increased reliability of records: Because positional errors are extremely small, you can precisely identify the shooting point. In infrastructure inspections and equipment management, you can clearly show “which location the photo corresponds to,” greatly enhancing the credibility of the records.

• Improved field work efficiency: Shooting a photo completes surveying and recording at the same time. The need to measure coordinates separately or take notes is eliminated, significantly reducing the time required for surveys and inspections. Human recording errors are also reduced.

• Faster information sharing: Accurate geotagged photos can be placed pinpoint on maps or drawings, making it easier to share the situation among stakeholders. By showing photos with their positions to remote colleagues or clients, you can intuitively convey field conditions and facilitate smoother communication.

• Advanced data analysis and utilization: Positioning photos can be combined with GIS (Geographic Information Systems) and CAD drawings. For example, you can accurately plot multiple acquired photos on a map to analyze distribution, or overlay photos on design coordinates to check construction status. When photo shooting positions are accurate, photogrammetry-based 3D reconstruction from multiple photos also benefits from improved model scale and alignment accuracy.

• Advantageous for fixed-point observation and temporal comparison: Using coordinate data from positioning photos, you can easily revisit exactly the same location photographed in the past. For periodic inspections aimed at observing long-term changes, photographing from consistent positions each time enables strict comparisons. If you plan to re-measure or re-photograph the same point in the future, positioning photo records serve as navigation hints.

• Effectiveness as evidentiary materials: Photos whose location information is recorded with centimeter-level precision are valuable as objective evidence. For example, in contexts requiring accuracy—such as proof of construction results, environmental surveys, or accident scene reports—high-precision geotagged photos provide strong backing. With reliable data, explanations to stakeholders and audit responses proceed more smoothly.

Use cases for positioning photos

So in what scenes are positioning photos specifically useful? Here are some examples.

• Inspection and maintenance of social infrastructure: When recording cracks or damaged spots on roads, bridges, tunnels, dams, and other structures, positioning photos are powerful. They can precisely indicate which part a photo corresponds to, avoiding confusion in later repair planning or report creation.

• Disaster site investigation and recording: In the event of earthquakes, heavy rains, or other disasters, positioning photos are effective for quickly recording and sharing damage conditions. Because coordinates can be acquired when photographing the damaged sites, photos taken by multiple personnel can be integrated on a map to create damage maps. Accurate geotagged photos are indispensable for emergency information sharing and relief planning.

• Construction record-keeping: Positioning photos are useful for documenting construction results on sites. For recording the locations of buried objects or evidence of installed structures, centimeter-level photos provide persuasive documentation during inspections. You can also verify whether construction locations match the design by comparing with design coordinates.

• Agriculture, forestry, and environmental surveys: Geotagged photos are useful in farm management, forest monitoring, and environmental surveys. For example, when recording pest outbreak sites in fields or animal traces in mountains, positioning photos allow precise identification of points later. Even across large fields, data organization is easier by matching photos to maps.

As shown above, positioning photos are useful in a wide range of field operations beyond civil engineering and construction.

• Site records for public agencies such as police and fire departments: At accident or fire scenes where time is limited, it is necessary to record conditions quickly. Using positioning photos enables you to leave accurate location records at the time of shooting, which assists later analysis and reporting. High-precision geotagged photos make it easier to reproduce scenes or analyze them on a map for police accident investigations or fire damage records.

Simple surveying with LRTK

LRTK is attractive not only for geotagging photos but also for enabling easy surveying with a smartphone. For example, you can use the phone’s camera and sensors to scan the surroundings and obtain three-dimensional point cloud data. By walking around a site while scanning, you can record terrain and structure shapes in a short time. From the acquired point cloud data, you can measure distances between two points on site or calculate volumes of embankments and excavations. Tasks that once required specialized contractors or expensive equipment can now be replaced by LRTK and a smartphone, making it a notable solution for simple surveying.

Furthermore, high-precision data obtained with LRTK can be combined with AR (augmented reality) technology to enable new applications. For example, you can provide AR guidance on site according to pre-registered positions on a drawing, or store the positions of buried pipelines as point cloud data and display them in AR during later excavation to perform digging safely. These are advanced applications, but the common foundation is the accurate positional information provided by LRTK.

Starting with highly accurate positional photo records and extending to surveying, point clouds, and AR, LRTK broadly supports the digitization of field operations. If cumbersome surveying and recording tasks can be completed on a smartphone at hand, operational efficiency will dramatically improve. Use high-precision positioning photos and simple surveying to experience the benefits of new solutions in your field.

Frequently asked questions

Q: What is the difference between a positioning photo and an ordinary smartphone geotagged photo? A: The main difference is that ordinary smartphone photo location data can have errors of several meters or more, whereas positioning photos use RTK technology to increase accuracy to a few centimeters. Also, standard smartphone photos do not record shooting direction, but positioning photos can save bearing information as well. In short, positioning photos provide more accurate and detailed location data.

Q: What level of positioning accuracy can be obtained? A: Depending on the environment, RTK-based positioning generally achieves very high accuracy of within a few centimeters horizontally (within a few centimeters (a few in)). Ordinary GPS can deviate by about 5-10 m (16.4-32.8 ft), but high-precision GNSS used for positioning photos enables much finer positional records. Note, however, that accuracy is affected by surrounding obstructions and sky visibility.

Q: Do I need specialized knowledge or qualifications to use LRTK? A: No. No special qualifications are required, and operation is simple. Attach the dedicated compact device to your smartphone and launch the app, then follow the on-screen instructions to shoot. It is designed so that people without formal surveying education can use it comfortably.

Q: What do I need to use positioning photos? A: Basically, you need the LRTK device itself and a compatible smartphone. Install the dedicated app on your phone and connect to the LRTK device to enable high-precision positioning. Correction services via the internet or satellite augmentation reception settings are handled automatically within the app, so users do not need to perform complex configurations.

Q: Can it be used in places without mobile signal coverage? A: Yes. LRTK supports the quasi-zenith satellite system (Michibiki)’s centimeter-level augmentation information (CLAS), so even outside network coverage you can receive correction signals from satellites and perform high-precision positioning. Of course, network RTK via internet is also available when within communication range.

Q: How can I view and share the photos I took? A: Positioning photos can be viewed on the smartphone together with a map and synced to a cloud service for viewing on a computer. By issuing a shareable link, recipients can view photos and location data in a web browser even if they do not have specialized software. You can share field-captured data on the spot with your company or partners, making reporting and communication smooth.

Q: Can photo data be used in other systems? A: Yes. Acquired positioning photo data is broadly usable. High-precision location information is included in the image file’s metadata, and compatible software can load and display it on a map. You can also export coordinate lists to import into GIS or CAD software. While LRTK’s cloud service can manage data, it is also easy to integrate the data with internal systems as needed.

Q: How about battery life and durability of the LRTK device? A: The LRTK Phone device has a built-in battery and can perform continuous positioning for several hours on a full charge. This is sufficient for typical field work. The device is also ruggedly designed for outdoor use, able to withstand some rain, vibration, and shock. You can confidently take it into the field and use it for extended periods.