For Surveying & GIS: Automatically Record Photo Location and Orientation with LRTK

Table of Contents

• Introduction

• What Are Photo Location and Orientation Data?

• Conventional Photo Recording Methods and Their Challenges

• Automatic Photo Location and Orientation Recording with LRTK

• On-site Benefits

• Conclusion: Simplified Surveying Expanded by LRTK

• FAQ

Introduction

When taking photos, recording when and where a photo was taken is extremely important. Especially in the fields of surveying and GIS (Geographic Information Systems), it is required not only to take on-site photos but also to accurately preserve the photo’s location and the camera’s direction (orientation). For example, in construction progress records or infrastructure inspections, if you cannot later determine “what was photographed at which location” for each image, the photo data cannot be fully utilized. If photos lack linked location or orientation data, it becomes time-consuming to indicate shooting points on a map or to identify the objects visible in the direction the photo faces.

On large sites you may take dozens of photos in a day, and without tag information you may later have to guess for each photo “from where and in which direction was this taken?” To efficiently manage and make effective use of on-site photos, a system that automatically records location and orientation at the time of capture is indispensable.

Traditionally, recording photo locations and orientations relied heavily on manual work, imposing a burden on field staff. However, recent advances in smartphones and positioning technologies have produced solutions that can automate this process. One such method uses a smartphone device called LRTK, which enables centimeter-level positioning. This article explains the importance of recording photo location and orientation and the traditional challenges, then introduces how LRTK automatically adds high-precision location and orientation data to photos and the benefits this brings on site.

What Are Photo Location and Orientation Data?

First, what are the “location information” and “orientation information” that can be attached to photos? Location information refers to the latitude and longitude (and altitude) data of the point where the photo was taken; for digital cameras and smartphones, this can be saved in the photo file as a GPS geotag. Orientation information indicates which direction the camera was facing when the photo was taken. Specifically, it is common to record the clockwise angle (0–360°) with north as 0° (true north); this is called the “azimuth” or “shooting direction.” In photo metadata (Exif), there is an item called “GPS Img Direction,” and by recording this angle there you can preserve the photo’s orientation as data.

Photos with location data (so-called geotagged photos) are easy to take with smartphones today. If the smartphone’s GPS is turned on, the photo app will automatically tag the image with latitude and longitude. However, in many standard smartphones orientation information is not recorded. Some camera apps or dedicated devices can record shooting direction, but this is not yet widespread in general smartphone use. If the Exif does not include orientation, you can only guess later “which way was that photo facing?” Also, GPS in smartphones and general digital cameras commonly has positioning errors on the order of 5–10 m (16.4–32.8 ft), which can cause plotted photo locations on a map to be misaligned. In urban areas with tall buildings or mountainous regions, satellite signals can be obstructed and errors tend to increase, so obtaining accurate on-site positions remains challenging. For use in surveying and GIS, it is desirable for photos to carry more accurate location and appropriate orientation data.

Conventional Photo Recording Methods and Their Challenges

Without advanced surveying instruments, several methods have been used to record photo location and orientation on site. One is manual note-taking. Each time a photo is taken, the photographer marks the shooting point on a map or drawing, measures orientation with a compass, and records notes such as “photographed facing XX direction.” Sometimes markers are placed within the photo or adjustments are made so the direction is visually apparent (e.g., including a compass in the frame). However, these methods are prone to human recording errors and omissions, causing confusion when organizing photos later. The process itself is cumbersome, and repeating positioning and note-taking for every shot is inefficient.

Another method is post-processing on a PC. Photos are taken in the field and later, on a computer, positions are assigned on mapping software based on memory, and shooting angles are estimated and written into metadata. With dedicated GIS software or tools you can embed location data into photos or display arrows for orientation, but this still largely relies on the person’s memory and manual input. If the situation at the time is not remembered accurately, correct alignment is difficult, and record reliability decreases over time. Even if handy GPS or surveying instruments recorded coordinates in the field, you still need to match those to the photo files later. Managing photo data and positioning data separately in conventional workflows makes photo management laborious, and cases where “only location tags were added by GPS but orientation wasn’t recorded” are not uncommon. As a result, valuable site photos can end up a difficult-to-use “treasure left unused” because they are not linked to map data.

Automatic Photo Location and Orientation Recording with LRTK

A groundbreaking solution that addresses these challenges is photo recording using LRTK (a smartphone RTK positioning system). (LRTK was developed by a startup originating from Tokyo Institute of Technology and is designed to meet the needs of Japanese fieldwork.) LRTK is a system consisting of a compact high-precision GNSS receiver that attaches to a smartphone and a dedicated app, turning a smartphone into a surveying instrument capable of centimeter-level positioning (cm level accuracy (half-inch accuracy)). When you shoot with LRTK, at the moment the shutter is released high-precision location information is obtained for each photo and the camera’s azimuth is automatically recorded. The captured images are saved on the smartphone, and their Exif metadata include longitude, latitude, height, and the camera’s orientation (azimuth). In other words, simply taking photos on site results in all the data for “when, where, and in which direction” being recorded.

The LRTK-enabled automatic geotagging & orientation recording offers the following features and advantages:

• Centimeter-level position accuracy (cm level accuracy (half-inch accuracy)): LRTK uses RTK-GNSS technology to improve photo location tags that were previously off by several meters (several ft) to errors at the level of a few centimeters (a few in). Even across large sites, you can accurately plot where each photo was taken on a map without misunderstanding positional relationships later. For example, in aerial photogrammetry using drones, if each photo already has high-precision coordinates, you can greatly reduce the on-site effort previously required for establishing control points (GCP installation).

• Automatic acquisition of azimuth: By linking with the smartphone’s electronic compass and gyro sensors, LRTK instantly obtains the shooting direction at capture. Troublesome compass measurements and handwritten notes become unnecessary. The recorded azimuth remains in the Exif data, so for each photo it is clear “how many degrees clockwise from north” the camera was facing.

• Stable orientation records based on true north: General magnetic compasses reference magnetic north, which can deviate from true north (geographic north) depending on the region. LRTK uses references and correction information from high-precision GNSS to obtain reliable orientation information on a true north basis. This ensures recorded angles align with the map’s north standard and prevents discrepancies in later analysis.

• Easy and reliable for one person: You simply attach the LRTK device to your smartphone and shoot, so specialized survey teams or complex procedures are unnecessary. Anyone can operate it like a smartphone camera while positioning and recording are processed automatically in the background. Field work speed is not reduced, and one person can carry out recording tasks efficiently.

On-site Benefits

Obtaining photos with location and orientation using LRTK brings significant benefits for field records and later data use. Below are main use cases and advantages.

• Construction records & progress management: In civil engineering and construction, it is routine to take periodic photos from before construction to completion. With LRTK, photos retain precise coordinates for each shooting location, so even on large sites you can manage shooting points without losing track. You can pinpoint the photo’s shooting location on a map later, making information sharing among stakeholders clear. Including shooting orientation also instantly shows “which direction the photo faces,” reducing the risk of confusing photos taken from the east with those taken from the west. Accurate tag information greatly improves the reliability of photos as evidence.

• Infrastructure inspection & fixed-point observation: For inspections of bridges, tunnels, roads, etc., repeated photos of the same location are often taken to track changes over time. With LRTK, the coordinates and camera azimuth recorded at the initial shoot mean that on subsequent visits it is easy to retake photos from the same position and angle. Using the app’s AR features, the phone can display a guide to align the camera with the direction of past photos, so even if the person in charge changes, the same composition can be reproduced precisely. For example, you can retake photos of a pier crack from exactly the same viewpoint as a photo taken years earlier and compare them—enabling high-precision fixed-point observation without extra effort. This allows correct assessment of deterioration and dramatically improves the reliability of inspection records.

• Asset management & report creation: LRTK is also powerful for managing photos of items whose positions matter, such as utility poles, signs, and boundary markers. The location data embedded in photo files can be imported to GIS software for mapping or automatically organized in an internal database. If you upload photo data to LRTK Cloud (cloud service), each photo’s shooting point is automatically plotted on a map, enabling geographic management of photo lists. Information such as photo latitude, longitude, and shooting date/time are linked and stored in the cloud, so you can view and share on-site photos with maps via a browser from an office PC, greatly streamlining report creation and ledger management. Because you can intuitively search for desired photos on a map, you no longer need to hunt through filenames asking, “Where is that equipment’s photo?”.

• Application to high-precision photogrammetry: LRTK is useful not only for tagging photos but also for full-scale photogrammetry. For example, when using drones or poles to take multiple photos and generating point clouds or 3D models with dedicated software, if each photo already contains high-precision shooting positions, positional alignment in post-processing becomes much easier. Traditionally, photogrammetry required placing multiple ground control points (targets) and performing corrections, but RTK-enabled photos can significantly reduce that burden. Even for simple ground-based photogrammetry using a smartphone, leveraging the position and orientation data obtained with LRTK makes it possible to obtain higher-precision point cloud data in a shorter time.

Conclusion: Simplified Surveying Expanded by LRTK

As described above, using LRTK makes recording photo location and orientation dramatically easier and expands the ways on-site photos can be utilized. The value in surveying and GIS lies not just in taking photos, but in linking those photos to maps and measurement data. LRTK is an all-in-one surveying tool anyone with a smartphone can use, supporting on-site measuring and recording tasks with features such as point cloud scanning and AR measurement in addition to photo recording.

Surveying work that once required specialists or expensive equipment can now be easily started by one person with LRTK. Why not begin by using location-tagged photos and eventually improve work efficiency with simplified surveying using LRTK? As a tool that promotes on-site DX (digital transformation), LRTK offers new possibilities for your operations. The use of such digital technology also aligns with industry-wide DX initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction policies.

FAQ

Q: How can the “orientation information” recorded in photos be used? A: The orientation information (shooting direction) included in a photo’s Exif is very useful when using photos in GIS software or map services. For example, placing photo icons on a map and showing arrows according to their orientation makes it intuitive to understand which direction each photo faces. Also, when revisiting the same site for re-photography, referencing the previous photo’s orientation to align the camera makes shooting from the same angle (fixed-point observation) easy.

Q: Smartphones can add location tags—what advantage does LRTK provide? A: Standard smartphone GPS has limited positional accuracy and can suffer meter-level errors under some conditions, causing subtle misalignment when placing photos on a map. LRTK uses RTK positioning to dramatically improve accuracy, recording photo positions with survey-grade precision of about ±2–3 cm (±0.8–1.2 in). This level of accuracy is a major advantage for applications that require consistency with survey maps or design drawings.

Q: Do I need specialized knowledge to use LRTK? A: No—LRTK can be used without special expertise. Its app is designed for intuitive operation, and starting positioning and capturing photos is guided on-screen. The device mounts to the phone with a one-touch attachment. The app displays the positioning status (how accurate it is) using color-coding, so first-time users can handle it without confusion.

Q: Can LRTK perform high-precision positioning in mountainous areas without radio or cellular coverage? A: Yes. LRTK supports high-precision positioning correction signals (CLAS) distributed by Japan’s satellite system “Michibiki,” allowing RTK corrections without Internet connectivity in areas without mobile coverage. This enables centimeter-level positioning even in mountainous or remote island environments where base-station networks are unavailable, so high-precision photo location recording is maintained.

Q: How is the LRTK device attached to a smartphone? Is it heavy? A: The LRTK terminal (GNSS receiver) attaches with a one-touch dedicated smartphone case or attachment. It has a built-in battery that supports several hours of continuous positioning on a single charge, so it’s reliable for long field work. Its size is compact with a thickness of about 1 cm (0.4 in), and the weight is only about 125–165 g, so attaching it to a smartphone is not burdensome. The built-in battery powers the device, and it connects wirelessly to the phone, eliminating the need for cables and making it easy to carry.

Q: What else can I do if I introduce LRTK? A: In addition to photo location and orientation recording, LRTK offers various surveying and measurement functions. For example, you can obtain point cloud data quickly with 3D scanning in conjunction with the smartphone camera, or perform stakeout navigation (guiding to target points with AR) based on acquired coordinates. Recorded data can be managed and shared in the cloud, so field records can be taken straight back to the office for use. LRTK functions as a total solution that enhances on-site productivity.