MADOCA-PPPで広がるスマホ測量 – LRTK活用で山間部もセンチメートル精度に

In recent years, as the demand for surveying and location information has increased, the importance of high positioning accuracy has grown even more. There are many situations that require centimeter-level accuracy (cm level accuracy (half-inch accuracy)), such as infrastructure work that needs to reconcile drawings with the site, disaster surveys that require precise terrain data, and forestry and agriculture that require precise parcel management. However, in remote areas outside communication coverage, such as mountainous regions, there has been a challenge in that conventional high-precision positioning methods are difficult to use. For example, techniques like Real-Time Kinematic positioning (RTK) assume a connection to a mobile communications network or base stations, so they are impractical deep in the mountains where radio signals cannot reach.

A service that is dramatically changing this situation is Japan’s high-precision positioning augmentation service, "MADOCA-PPP." This article explains what MADOCA-PPP is, gives a technical overview, and describes how it overcomes the limitations of standalone positioning. It also introduces how the new positioning solution "LRTK," which combines a smartphone and a GNSS receiver, together with MADOCA-PPP, enables centimeter-level surveying even in mountainous areas. Finally, through concrete use cases in infrastructure maintenance, forest road development, and disaster surveys in mountain regions, we explore the effects of its introduction and the benefits it brings to the field.

MADOCA-PPPとは何か – 日本発の高精度測位補強サービス

MADOCA-PPP is a high-precision positioning augmentation service that uses Japan’s Quasi-Zenith Satellite System, "Michibiki." "MADOCA" stands for “Multi-GNSS Advanced Demonstration tool for Orbit and Clock Analysis,” and as the name implies, it is based on technology that analyzes data from multiple Global Navigation Satellite Systems (GNSS) to precisely correct orbit and clock errors. "PPP" means Precise Point Positioning, a method that enables high-precision positioning with a single receiver. MADOCA-PPP uses data from GNSS observation networks deployed domestically and abroad to compute satellite orbit and clock errors and ionospheric effects, and it distributes those correction informations directly to users from the Quasi-Zenith Satellites. On the user side, a compatible GNSS receiver receives these corrections and incorporates them into its position calculations, enabling a standalone receiver to achieve decimeter-level accuracy (within several tens of centimeters).

In Japan, Michibiki also provides a centimeter-level augmentation service known as CLAS, which is well known. While CLAS primarily targets Japan and achieves real-time centimeter-level accuracy through detailed regional correction models, MADOCA-PPP was developed as a more general-purpose augmentation service available over a wider area (the Asia–Oceania region). For example, in areas around Japan offshore or in mountainous regions of neighboring countries where high-precision reference station networks were not established, MADOCA-PPP can provide augmentation as long as Michibiki signals reach the area. MADOCA-PPP began trial operation in 2022 and entered full operation in April 2024; it is a new service expected to be applied in various fields such as autonomous driving, precision agriculture, and disaster monitoring.

通信不要・広域カバー – MADOCA-PPPで単独測位の限界を超える

In places with limited communication infrastructure, such as mountainous areas or remote islands, conventional positioning methods faced major constraints. General GNSS standalone positioning (like unaugmented GPS), even in ideal environments, cannot avoid errors of several meters (about 5–10 m (16.4–32.8 ft)), making it unsuitable for high-precision surveying. High-precision positioning typically uses RTK or network RTK (for example, VRS), which rely on receiving corrections from reference stations; these require continuous communication, so they cannot operate at sites without cellular or radio links. Even in areas with mobile coverage, building a network that covers vast mountainous regions is unrealistic, and accuracy degrades as distance from base stations increases.

MADOCA-PPP is a solution that breaks through these standalone positioning limits. Its greatest advantage is that it can achieve high precision without relying on external communication. Because MADOCA-PPP correction information is broadcast directly from the Quasi-Zenith Satellites, users in mountain sites can receive high-precision augmentation without connecting to the internet or radio communication. This holds true for areas where communication infrastructure has been cut off by disasters and for deep forests that normally receive no signal. As long as the satellites are visible overhead, positioning accuracy can be improved in real time—bringing the advantage of “if the sky is open, you can measure anywhere.”

Furthermore, MADOCA-PPP is designed to provide a uniform accuracy improvement effect over a wide area. Within the service area, simply receiving the correction information can be expected to provide equivalent accuracy anywhere in the country, eliminating concerns about accuracy degradation due to distance from reference stations. For example, in wide-area surveys of mountainous regions or patrol inspections of long-distance infrastructure (such as power lines or roads), it is possible to obtain stable positional accuracy while moving. Because it can be used not only within Japan but throughout the Asia–Pacific region, it is also applicable to surveying projects in overseas mountain areas or positioning on the open sea. MADOCA-PPP reduces standalone positioning errors of several meters to below several tens of centimeters, and by eliminating the need for infrastructure development and communication costs to achieve this, it opens new possibilities in situations where improving accuracy had been difficult.

However, there are points to note when putting MADOCA-PPP into practical operation. One is the convergence time required for positioning accuracy to stabilize. Because the PPP method gradually models errors, when starting positioning for the first time or reinitializing after losing satellite signals for a long period, a convergence time of several minutes to several tens of minutes is required (a general guideline is that horizontal position converges to 30 cm or less (11.8 in or less) in about 20–30 minutes). Therefore, it is effective to turn on the receiver before beginning work so that accuracy can improve while moving or preparing. With an increase in the number of Michibiki satellites (a seven-satellite configuration), efforts are underway to shorten convergence time—for example by additionally broadcasting wide-area ionospheric error information—so it is expected that centimeter-level accuracy will be reached more quickly in the future.

スマホ×GNSS受信機で実現するMADOCA-PPP測位 – LRTK活用の利便性

The advent of MADOCA-PPP has greatly expanded opportunities for high-precision positioning. However, to easily enjoy these benefits in the field, you need not only the positioning service but also the devices and tools to use it. While general smartphones are equipped with GNSS receivers such as GPS and GLONASS, consumer smartphone GNSS tends to be limited in the frequency bands and signals it can receive, and cannot handle MADOCA-PPP correction signals (the L6 band) or multi-frequency high-precision positioning. Also, smartphone-only positioning accuracy, as noted above, remains on the order of several meters. Enter the high-precision GNSS receivers that can be paired with smartphones: the "LRTK" series.

LRTK is a solution consisting of an ultra-compact GNSS receiver device that can be used with a smartphone and a dedicated app, combining the convenience of a smartphone with survey-grade accuracy. For example, the LRTK Phone is a product that, by simply attaching a device with an integrated antenna and battery to a smartphone, enables centimeter-level positioning using Michibiki’s CLAS or MADOCA-PPP. Physically integrating with the smartphone removes the hassle of cable connections and provides excellent portability, so you can pull it out in the field and start measuring immediately. In addition, a dedicated smartphone app is provided for intuitive operation of positioning start/stop and data recording. The high-precision coordinates obtained during positioning can be plotted on a map in real time or linked with photos and notes for storage, dramatically streamlining field survey recordkeeping.

There are many advantages of smartphone surveying using LRTK that conventional surveying equipment cannot offer. The main points are summarized below.

• 手のひらサイズで高精度: LRTKデバイスはスマートフォンと同程度の大きさ・重量で、ポケットに収まるコンパクトさです。従来の据置型GNSS受信機や大型アンテナを運ぶ必要がなく、険しい山道や災害現場でも機動力を発揮します。登山道の踏査や斜面調査でも、重機材の持ち運びに煩わされることがありません。

• 一人で簡単測量: スマホとLRTKを専用ポール（もしくは一脚）に取り付ければ、一人でも安定した精度で測位が可能です。高さのオフセット（地面から機器までの高さ）はアプリ上で自動補正されるため、ポールの長さを厳密に気にせずとも正確な標高が取得できます。複雑な操作を必要としないので、熟練の測量士でなくとも扱いやすいという利点もあります。

• リアルタイムで結果が得られる: 測定ボタンをタップするだけで、その瞬間の緯度・経度・高さを含む座標データが即座に得られます。後からオフィスでデータを処理して座標計算する、といった手間はありません。測ったその場で結果を地図に反映したり、設計図と照合して確認したりできるため、判断のスピードが上がります。

• 悪条件下でも安定した測位: LRTKは複数周波数・マルチGNSS対応の高性能アンテナを備えており、山間部で木々に囲まれた場所や谷間でも衛星をできる限り捉えて測位します。従来の単一周波数GPSでは位置が不安定になりがちな環境でも、できるだけ安定したセンチメートル級の精度を維持できるよう設計されています。これにより、「森の中では精度が出ない」「谷筋では使えない」といった制約が大幅に緩和されます。

• スマホの拡張機能との連携: スマートフォン側のカメラやLiDARセンサーとも組み合わせることで、写真測量や簡易3Dスキャン、あるいはARによる現地への図面投影など、位置情報を活用した幅広い現場ソリューションが可能です。例えば、高精度な位置座標付きの写真をクラウドに共有すれば、オフィスの専門家に現場の状況を即座に伝えられます。また、スマホ画面上で設計データと自分の現在位置を重ね合わせ、現場で施工箇所を可視化するといったことも容易です。

In this way, the combination of MADOCA-PPP and LRTK is creating an environment where "anyone, anywhere, immediately" can perform precise positioning. So in which specific field situations does this smartphone surveying technology demonstrate its strengths? Next, we will look at use cases in mountainous areas and the effects brought by their introduction.

山間部の現場で広がるユースケース – インフラ保守・林業・災害調査など

High-precision positioning using smartphones and LRTK is beginning to be widely used in mountain-site applications that were previously difficult to survey. Here are several representative use cases.

• インフラ設備の保守点検: For infrastructure running through mountainous areas—roads, bridges, power line towers, etc.—accurate location information is required for periodic inspection and repair. Traditionally, to grasp the locations of facilities in remote mountain areas, one had to rely on paper maps and GPS with meter-level errors, or bring in large surveying equipment. By adopting smartphone surveying compatible with MADOCA-PPP, maintenance personnel can record accurate coordinates of each facility on site and pinpoint deteriorated locations. For example, in pipeline inspections along mountain slopes, knowing anomaly coordinates to centimeter-level accuracy allows for precise planning of later repairs. Measurement results can be reflected on digital maps on the spot, reducing the workload of preparing reports.

• 林業における境界確認・作業計画: In remote woodlands, forestry cooperatives and workers have struggled with boundary confirmation and planning of logging roads. Surveys often relied on measuring tapes and compasses to place boundary stakes or select trees for thinning, risking disputes due to positional errors. With smartphones enabling high-precision positioning, it is possible to record exact latitude and longitude for points within forests. This allows clear sharing of boundary lines between one’s own forest and neighboring lands on maps, and meticulous planning of planting and thinning areas. In new forest road planning, one can walk route candidates on site while the smartphone draws a track, then import that directly into CAD drawings—reducing the need for surveyors to perform extensive follow-up measurements.

• 災害現場での被災状況調査: Mountainous areas are prone to natural disasters such as landslides, slope failures, and river flooding from heavy rain. Rapidly grasping post-disaster conditions requires accurate field data collection. Smartphone surveying enables technicians responding to emergencies to conduct efficient surveys with small teams, even when visiting hazardous sites. For example, after a cliff collapse, measuring multiple endpoint locations of the collapse area allows estimation of the volume of displaced soil and identification of hazardous zones. Where several-meter errors could affect secondary disaster prevention plans, recording conditions at centimeter-level accuracy drastically improves the precision of area designation. Because positioning works even outside communication coverage, there is no worry that accurate data cannot be obtained until returning to headquarters, improving the reliability of initial response. Coordinates-attached photos and survey data obtained on site can be shared with relevant agencies the same day and become valuable materials for recovery planning.

In these use cases, the introduction of smartphone surveying has produced the following effects.

• 作業効率の飛躍的向上: Because one person can complete surveys quickly, the manpower and time required for field work have been greatly reduced. Eliminating the need to transport personnel and heavy equipment along mountain trails contributes significantly to efficiency.

• 測量コストの削減: Survey tasks that previously required outsourcing to specialists or purchasing expensive equipment can now be accomplished by introducing a smartphone and an LRTK device, reducing cost burdens. The lack of communication fees also contributes to long-term operational cost reduction.

• データ精度と信頼性の向上: Obtaining centimeter-level data improves the accuracy of planning and decision-making. Rework and design changes due to errors are reduced, and the reliability of reports from the field increases.

• 安全性の改善: Shorter work times and smaller teams reduce risks in hazardous sites. Reducing the time workers need to remain at dangerous locations contributes to their safety.

まとめ – スマホ測量が切り拓く新たな可能性とLRTK導入のすすめ

Centimeter-level surveying that was once difficult, including in mountainous areas, is becoming a reality across many fields. The combination of Japan-origin satellite augmentation technology MADOCA-PPP and smartphone-based LRTK solutions has made usage possible not only for surveying professionals but also for infrastructure technicians, disaster response staff, and forestry workers. The advantage of being able to achieve high-precision positioning without depending on communication environments has the potential to significantly change how field operations are conducted in the coming DX (digital transformation) era.

Of course, introducing new technology requires field operational verification and human resource development, but the ease of smartphone surveying lowers these barriers. Intuitive apps and portable devices are overturning the conventional notion that surveying can only be handled by specialists. In fact, some local governments and companies have already begun incorporating LRTK-based surveying workflows, achieving both improved efficiency and data accuracy.

Now that high-precision positioning technology is available on everyday smartphones, the range of fields benefiting—from infrastructure maintenance in mountain areas to disaster response—will continue to expand. If in your work you feel that "surveying takes too long" or "securing accurate location information is a challenge," consider introducing smartphone surveying with MADOCA-PPP and LRTK. By proactively adopting the latest technologies, you can dramatically improve fieldwork efficiency and accuracy and create new value.