Ideal for Infrastructure Inspections! An App That Can Capture High-Precision Geotagged Photos

Table of contents

• Challenges of photos and location information in infrastructure inspections

• What are high-precision "geotagged photos"?

• Main benefits offered by geotagged photos

• Achieving high-precision coordinates with smartphones and tablets

• Use cases and effects for infrastructure inspections

• Accelerating on-site DX with LRTK simple surveying

• FAQ

Challenges of photos and location information in infrastructure inspections

As social infrastructure ages, the importance of regular inspections and maintenance of structures such as bridges and tunnels is increasing. Inspection needs are expected to grow further, for example with close visual inspections of bridges and tunnels becoming statutory tasks. To carry out infrastructure inspections efficiently with limited personnel, the use of digital technologies on site has become indispensable. One approach that has attracted particular attention is to attach coordinate information to the photos taken during inspections. Traditionally, when recording and managing photos taken at inspection sites, it was common to handwrite the shooting locations on paper drawings or assign numbers to photos and correlate them with separate logs. However, this method has several problems.

• Information tends to become person-dependent: Recording and interpreting inspection data often relies on the experience and intuition of individual personnel, making sharing and handing over information within the department or to succeeding staff difficult.

• It becomes hard to determine photo locations: When photos are reviewed after some time, it is often difficult to tell which part of the structure the image shows. Relying solely on report descriptions or the memory of the person in charge can lead to not knowing “where this photo was taken,” resulting in duplicated work.

• Recording work is cumbersome and prone to mistakes: Operations that require manually noting the shooting location for each photo are very cumbersome and create opportunities for human error. Mistyped numbers or forgotten notes can lead to mismatches between photos and locations. In infrastructure inspections that handle many photos, such mistakes can greatly affect report accuracy.

• Comparing inspection histories is not easy: If photos and notes are managed in paper ledgers or separate files, it is difficult to cross-check past inspection results with new ones to track deterioration. If photo locations remain ambiguous, it can also be hard to re-examine exactly the same spot in the next inspection.

The use of “geotagged photos” is expected to be the key to solving these problems.

What are high-precision "geotagged photos"?

As the name implies, “geotagged photos” are records in which photos have coordinate information (latitude, longitude, elevation, etc.) added to them. Each photo is automatically tagged with numerical coordinate data indicating “where it was taken.” Unlike vague location records in traditional paper ledgers or photo albums, geotagged photos leave objective, precise location information, dramatically improving the reliability of inspection records.

There have been methods to record latitude and longitude in photos using GPS-capable cameras or smartphones. However, ordinary GPS typically has positioning errors on the order of several meters to more than ten meters; for smartphone-built-in GPS, the accuracy is roughly a radius of 5-10 m (16.4-32.8 ft). Therefore, the precision is insufficient to pinpoint fine damage locations within a structure, and issues such as “the location described in the report differs from the actual location” or “the photo alone cannot accurately identify the damaged part” have been pointed out. In contrast, with high-precision geotagged photos, coordinates with errors of a few centimeters (a few inches) can be recorded at the moment of shooting, greatly expanding the accuracy and applicability of the records. For example, writing “crack at the base of pier A2 of XX bridge” in a report still leaves ambiguity, but if numeric coordinates are appended, anyone can unambiguously identify the same point. If each photo contains accurate position information as a tag, it becomes immediately clear “which location the photo shows” when reviewing photos later.

Main benefits offered by geotagged photos

Introducing geotagged photos brings the following benefits to infrastructure inspection operations.

• Objective, consistent location identification: By attaching numerical, accurate coordinates to photos, ambiguity about “which location” in a report is resolved. There is no need to rely on textual descriptions or human memory, and anyone can identify the same point, reducing mismatches and communication errors between field and office.

• Improved traceability of inspection history: If damage points and measurement points are recorded with coordinates as tags, you can re-inspect the exact same location in subsequent inspections and quantitatively compare deterioration over time. Visualizing temporal changes on maps or drawings makes it easy to analyze damage distribution and trends, enabling advanced utilization.

• Streamlined recording and error reduction: If location information is recorded automatically when a photo is taken, workers no longer need to take notes or later write locations on photos. This prevents handwriting errors and input mistakes, improving efficiency and recording accuracy for both field and office. As a result, report creation and ledger organization time is reduced.

• Easy digital data integration: Coordinate data obtained as numbers can be smoothly linked with electronic maps, CAD drawings, GIS (geographic information systems), bridge management systems, and so on. You can easily plot photo locations on a map or register them with positional data in asset databases, facilitating inter-departmental information sharing and integrated data management.

Achieving high-precision coordinates with smartphones and tablets

How can you obtain high-precision geotagged photos? The key is the use of satellite positioning technology RTK (real-time kinematic). RTK corrects satellite positioning errors from systems like GPS and GLONASS in real time and can determine positions with centimeter-level accuracy. Traditionally, using RTK in the field required specialized GNSS receivers and base station sets—expensive equipment. However, recent miniaturization of hardware and advances in communication infrastructure have made it possible to perform precise RTK positioning with smartphones and tablets.

Specifically, by connecting a small high-precision GNSS receiver to a smartphone or tablet and receiving correction information over a network (for example, via NTRIP services), the error of the built-in GPS, which used to be 5-10 m, can be reduced to a few centimeters (a few inches). For example, with a dedicated app for positioning, you can measure your current location to centimeter-level precision each time you take a photo and automatically attach that coordinate to the photo data. No complex operations are required—just press the positioning start button to obtain high-precision location information in real time. This enables on-site personnel to easily perform survey-level position recording without calling in a specialized surveying team.

Moreover, if you integrate the smartphone’s built-in electronic compass and orientation sensors, you can simultaneously record the direction and angle when the photo was taken. For example, information such as “this equipment was photographed from the northeast” is saved with the photo, clarifying “from which direction it was viewed” when reviewing images later. With such added information, the combination of a smartphone, dedicated devices, and apps makes it possible to collect precise data all-in-one. The acquired data can also be uploaded to the cloud immediately for sharing, greatly reducing the time for photo organization and manual ledger entry after returning to the office. In post-disaster damage surveys, in particular, quickly sharing photos and location information from the field to create damage maps can enable prompt response and deliver significant benefits.

Use cases and effects for infrastructure inspections

Utilizing high-precision geotagged photos and point cloud data can bring various efficiencies and enhancements to on-site infrastructure inspections. Below are representative use cases.

• Use in close visual inspections: In close visual inspections of bridges and tunnels, many photos are taken at each inspection point. If these photos include coordinate information, it becomes possible to accurately identify “which photo shows which part of the structure” on maps or drawings when preparing reports later. For example, if a crack in a pier is recorded with a geotagged photo, the exact same spot can be easily found in the next periodic inspection, making post-repair re-inspection efficient. Because teams can reliably share locations where anomalies were found, the basic accuracy of inspections improves.

• Use in quantitative inspections such as thickness measurement: Geotagged records are also effective for quantitative inspections using non-destructive testing devices like ultrasonic thickness gauges to measure steel corrosion. Previously, measurement locations were marked or roughly noted on drawings, but managing measurement results with high-precision coordinate tags allows you to accurately track “which value was measured at which location” over the long term. For example, when measuring thickness at multiple points on tanks or girders annually, registering each point’s coordinates enables accurate year-on-year comparison of corrosion progression. Being able to spatially identify where thickness reduction exceeds thresholds helps prioritize repairs and evaluate safety.

In addition to the above, accumulated geotagged inspection data allows overlaying multiple inspection results on maps for comprehensive evaluation. It becomes easy to correlate past crack occurrences with current electrical equipment inspection results, enabling analyses and the construction of a digital management ledger (digital twin) that provides an overall view of the structure. Centralized, time-series analysis of inspection data can lead to early detection of anomalies and predictive maintenance. In the future, aggregated integrated data may be analyzed by AI to automatically suggest degradation trends and repair priorities.

Accelerating on-site DX with LRTK simple surveying

To fully realize the value of high-precision geotagged photos, it is important to acquire location information with as high a degree of accuracy as possible. Fortunately, networked RTK-compatible compact GNSS receivers and positioning services are now abundant, and centimeter-level positioning that was once left to specialists can now be handled on site by anyone. A representative example is the solution “LRTK,” which turns smartphones into one-person surveying instruments. With LRTK, on-site infrastructure inspection staff can perform simple surveying themselves and immediately reflect precise position data in photo records.

For example, if you pre-measure multiple points around a structure using an LRTK-compatible GNSS device and app, you can save photo coordinates in the same coordinate system as the design drawings. This makes it easy to precisely show photo locations on drawings or BIM models and use them for planning repairs and verifying work quality. Combined with a smartphone’s built-in LiDAR scanner, it may even be possible to walk around a site and quickly 3D-scan large structures to obtain detailed point cloud models. If the acquired point cloud data are tagged with high-precision coordinates, they can be used for quantitative evaluation of deformation over time and post-construction as-built checks. Furthermore, because centimeter-grade accuracy is available, integration with AR (augmented reality) technologies advances. For example, viewing the site through a smartphone camera could highlight previously recorded damage locations, helping prevent on-site oversights. Also, tasks that previously required multiple people for surveying and recording can increasingly be completed by a single person, helping alleviate labor shortages and reduce costs.

LRTK thus holds great potential as a platform for on-site DX (digital transformation). With high-precision coordinate information as a foundation, data utilization in infrastructure maintenance and management will advance to a new level. It may seem difficult, but now anyone with a smartphone and a small device can handle centimeter-level positioning. Why not take this opportunity to start on-site DX by utilizing high-precision geotagged photos? By using high-precision location data, you can further enhance the safety and efficiency of infrastructure maintenance and management.

FAQ

Q: What is LRTK? A: LRTK is the name of a solution for performing high-precision positioning using smartphones. It leverages networked RTK (real-time kinematic) technology and combines a small GNSS receiver with a dedicated app so that anyone can easily achieve centimeter-level positioning. Compared to traditional large surveying instruments, it is much more user-friendly and aims to enable “simple surveying by one person” in various field situations, including infrastructure inspections.

Q: How much more accurate is it compared to smartphone GPS? A: Typical built-in smartphone GPS can have an error of about 5-10 m (16.4-32.8 ft) even on flat ground. By using an RTK-capable GNSS receiver and a dedicated app, the error can be dramatically reduced to a few centimeters (a few inches). In other words, it provides several hundred times better positional accuracy. For example, when recording damage on a bridge, smartphone GPS alone can only give a rough idea of which part of the bridge is affected, but RTK can identify the location down to the level of a single crack.

Q: What equipment and conditions are required for high-precision positioning? A: You need a smartphone or tablet, a dedicated high-precision GNSS receiver, and a communication environment to obtain correction information over the network. The GNSS receiver connects to the smartphone via Bluetooth or cable. Once you connect to a correction information service from the dedicated app, you can acquire high-precision geotagged photos just like taking normal camera shots. It is also important to be in an environment where GNSS satellites can be received stably outdoors (satellite signals can be weak behind tall buildings or inside tunnels).

Q: Can it be used in environments where satellites cannot be received, such as inside tunnels or indoors? A: RTK positioning is difficult in environments where satellite signals cannot reach at all, but there are useful functions for such situations. For example, some LRTK apps have a mode that uses the camera and inertial sensors to perform relative position tracking indoors (estimated error of about 1% of travel distance). This can complement position recording in short satellite-denied sections. However, cumulative error grows over long distances, so it is recommended to re-establish high-precision outdoor positioning as needed for correction.

Q: How can the acquired data be managed and shared? A: Geotagged photos and point clouds can be uploaded to the cloud on site and shared within the team. With internet access, you can send photos and location data from the field to the office in real time and use them immediately for reporting. Data can also be exported in CSV or PDF formats, making it easy to import into internal asset management systems or GIS software. Photos that used to be pasted into paper ledgers can be managed centrally as digital data.

Q: Can it be used without specialized knowledge? A: Yes. It is designed so that users without expertise in high-precision positioning can operate it. Dedicated apps have simple interfaces—starting/stopping positioning and taking photos can be done with a single tap. Complex settings are automated, and precise positioning can be completed with intuitive smartphone operations. While an initial basic training session is reassuring, in many cases a few hours of training are sufficient to learn. Once you start using it, you will likely find it hard to go back to the cumbersome traditional recording methods.

Q: How do I introduce high-precision geotagged photos? A: You need a dedicated high-precision GNSS receiver (for example, a smartphone-mounted LRTK Phone) and a smartphone app. The LRTK Phone is a small device that attaches to a smartphone; when connected via Bluetooth or cable, the smartphone becomes a high-precision GNSS positioning terminal. The smartphone app can be downloaded from the official website or app stores. After connecting the GNSS receiver to the smartphone and configuring RTK correction information in the app, you are ready to go. Once initial setup is complete, just start positioning in the app and take photos to obtain high-precision geotagged photos. For detailed installation procedures and purchasing information for required equipment, please check the official website or contact support.