Explaining the Difference Between 2D Road Ledger-Attached Maps and Road Ledger Maps in 5 Minutes

In road management practice, the terms "2-dimensional road ledger attached map" and "road ledger map" are sometimes used interchangeably. Both are drawings used to grasp road areas, widths, structures, occupancies, roadside conditions, and so on, but when their purposes and uses are organized, there are situations where they should be treated as the same and situations where it is better to consider them separately. In particular, it is important for those responsible for digitizing existing materials, those responsible for updating the road ledger, and those who want to link field inspections with drawing management to understand this difference.

Table of Contents

• What is the difference between the 2D road register attached map and the road register map

• Basic role of the road register map

• Basic role of the 2D road register attached map

• Why they are often confused in practice

• Five perspectives to clarify the differences

• The granularity of information to consider in road management

• Points where differences arise in update operations

• Points to note regarding digitization and GIS integration

• How to link with on-site verification

• Summary: Understanding the differences improves the accuracy of road management

What is the difference between the 2D road ledger attached map and the road ledger map?

In a single sentence, the difference between a 2D road ledger supplementary map and a road ledger map is that a road ledger map typically refers to the drawings that make up the road ledger as a whole, while a 2D road ledger supplementary map is usually treated as one of those drawings that shows planar positional relationships.

The term "road ledger maps" may be used broadly to refer to drawing materials used by road administrators to grasp and manage the condition of roads. These are drawings that organize information necessary for road management—such as the road area, route name, start and end points, width, length, road right-of-way, public–private boundaries, side ditches and gutters, sidewalks, bridges, slopes, retaining walls, intersections, and encroachments. In practice, they are handled in various forms, including paper drawings, image-based drawings, PDF drawings, CAD drawings, and drawings linked with map information.

On the other hand, the 2D road ledger attached map is easier to understand if regarded as a plan view attached to the road ledger. It is a drawing organized so that the road centerline, area lines, widths, road structures, boundaries, and map features can be checked on a plane. It does not handle 3D information and, because it manages positional relationships mainly as seen from above, it is a format that is highly compatible with traditional paper drawings, PDF drawings, and 2D CAD drawings.

In other words, "road ledger maps" can be used as a general term for drawings related to the road ledger, and among these, "2D road ledger attached drawings" refer to materials that organize road information as plan views; thinking of them this way makes practical organization easier. However, terminology is not necessarily completely standardized across municipalities, organizations, contract specifications, or past drawing management rules. Therefore, it is important not to judge by the name alone, but to confirm what is shown on the drawing and which tasks it is intended for.

The Basic Role of the Road Register Map

The main role of road ledger maps is to enable the current conditions of roads under management to be captured as drawings. Roads are public infrastructure used daily, and it is necessary to accurately manage their zones, structures, appurtenances, occupancy status, and improvement history. Road ledger maps are used as fundamental reference material for that management.

In road management, there are many situations where it is necessary to confirm where a given route runs from and to, how far the road area extends, what the width is in meters, where sidewalks and side gutters are located, and where structures such as bridges and retaining walls exist. Being able to verify this information on drawings makes it easier to carry out tasks such as responding to inquiries, issuing occupancy permits, planning construction, planning repairs, responding to disasters, maintenance management, and boundary verification.

Also, a road ledger map is not merely a drawing for viewing. It may serve as a management record under the Road Act and is used to ascertain the history of past changes to road areas, openings to traffic, improvement works, widening, closures, realignments, and the like. Therefore, consistency between current conditions and past records, the correspondence between drawings and reports, and the consistency of route numbers and reference numbers are important.

If road ledger maps have not been maintained or remain outdated, on-site road conditions may not match the drawings. For example, a sidewalk may have been installed on site but not reflected in the drawings, the lines delineating the road area may be outdated, the positions of side ditches or waterways may be misplaced, or the post-improvement shape of an intersection may not be shown. Such discrepancies can lead to rework during field verification and to differences in understanding among stakeholders.

Therefore, road ledger maps should be treated not as "drawings created in the past" but as "documents for continuously updating the basic information for road management."

Basic Roles of the 2D Road Ledger Attached Map

The role of a two-dimensional map attached to the road ledger is to clearly show the planar information accompanying the road ledger. Being two-dimensional, it is better suited to confirming planar positions, alignments, zones, widths, and the arrangement of features than to verifying heights or three-dimensional shapes.

In practical road management, situations are often first assessed in plan view. Confirming which route and which section contains the location in question, how the road boundary line adjoins private property boundaries, where sidewalks and side ditches are located within the road area, and how the road width changes at intersections and on curves can often be sufficiently understood from two-dimensional supplementary drawings.

Two-dimensional road ledger attached maps are easy to handle as paper drawings and are also characterized by being easy to store as PDFs or image data. Many past road ledger materials are often kept on paper, and it is common practice to scan them into PDFs and, when necessary, make them searchable by index or route number. Also, if they are converted to 2D CAD, it becomes easier to check distances and areas, edit lines, update drawings, and overlay them with other plan views.

On the other hand, 2D road ledger maps have limitations. Information in the vertical direction, undulations of the road surface, slopes of embankments, the space under bridges, the height of retaining walls, differences in pavement level, drainage gradients, and so on may not be sufficiently represented by two-dimensional drawings alone. Therefore, while 2D road ledger maps are extremely important as a basis for road management, when seeking to grasp the three-dimensional conditions on site it is desirable to use them in combination with photographs, survey results, cross-sectional drawings, point cloud data, and field inspection records.

Two-dimensional road ledger attachment maps serve as the starting-point materials for road management. They function as basic drawings for grasping the target location before visiting the site, organizing the contents of inquiries, and identifying discrepancies between existing ledgers and current conditions.

Reasons They Are Often Confused in Practice

The reason why two-dimensional road ledger attached maps and road ledger maps are easily confused is that both are drawings related to the road ledger, and in practice the same materials are sometimes referred to by either term. In materials that have been managed as paper drawings historically, the drawing title may say "road ledger map" even though the content is actually a planar attached map. Conversely, something labeled as a "road ledger attached map" may, in practice, be treated as a "road ledger map".

Also, since the road ledger is often used with the record and drawings as an integrated set, the distinction between terms tends to become ambiguous. The record contains attribute information such as the route name, length, width, road classification, date of designation, and date of commencement of use, while the attached drawings show their location and shape. Depending on the person in charge, some may refer to all of these collectively as the road ledger map, while others may call only the drawing portion the road ledger attached drawing.

Furthermore, as digitization advances, naming inconsistencies are likely to occur. When scanned PDFs of paper road ledger maps, management drawings with embedded images, 2D CAD-converted attached drawings, and map-viewable road ledger layers are managed together in the same folder or system, it becomes difficult to distinguish them based only on file names or on-screen labels.

Even in commissioned work, the wording of the specification can lead to different interpretations. When a specification states "update the road ledger map," unless you confirm whether it actually refers to corrections to the two-dimensional attached road ledger map, whether it includes checks for consistency with the survey records, whether it includes corrections to the road boundary lines, or whether it includes digitization into electronic data, discrepancies in the scope of deliverables can arise.

To prevent such confusion, it is important not to judge by the name alone. It is necessary to specifically confirm the drawing's role, the information it contains, the items to be updated, the delivery format, and the relationship with on-site verification, and to ensure a shared understanding among stakeholders.

Five perspectives for organizing the differences

To judge the difference between 2D road ledger attached maps and road ledger maps in practice, it is easier to understand if you organize the issue from several perspectives. The first thing to look at is the scope. Road ledger maps often refer to all drawings related to the road ledger, whereas 2D road ledger attached maps focus on attachments as plan views. Even when the term "road ledger map" is widely used, if the actual work target is only updating plan views, the work can be considered closer to maintaining 2D road ledger attached maps.

Next is the nature of the information described. Road ledger maps are treated as documents that compile the drawing information necessary for road management, and may include routes, zones, widths, structures, land features, boundaries, and so on. Two-dimensional road ledger maps focus on organizing information that can be confirmed on a plane. Details such as elevation, cross sections, three-dimensional shapes, and underground buried objects may need to be supplemented by separate drawings or other materials.

The third is the use case. Road ledger maps are widely used as basic reference materials for road management, including administrative procedures, maintenance, construction planning, boundary verification, and responding to inquiries. Two-dimensional road ledger maps are especially effective as plan views for confirmation tasks such as verifying the location of the target section, confirming areas, checking roadway width, conducting preliminary checks before field surveys, and identifying sections to be updated.

The fourth is the data format. Road ledger maps exist in various formats such as paper, PDF, images, CAD, and map information data. Two-dimensional road ledger attached maps are likewise managed in diverse formats, but because they are two-dimensional it is important whether they can be edited and viewed as plan drawings. When digitizing, it is necessary to distinguish whether simply converting to PDF is sufficient, whether to assign coordinates so they can be overlaid on a map, or whether to make them editable as CAD data so that lines and text can be edited.

The fifth point is the approach to updates. When updating road ledger maps, consistency with the records and related documents, not just the drawings, may be required. For updates to the two-dimensional road ledger supplementary maps, it is important to ensure that information on the plan view—such as road shape, boundary lines, structures, map features, annotations, map frame, and index—is correctly reflected. However, if only the supplementary maps are corrected and the records remain outdated, inconsistencies will remain in the road ledger as a whole. Therefore, in practice it is essential to update them while being mindful of the relationship between the two.

Information Granularity to Consider in Road Management

In road management, what matters more than the name of the drawing is determining what level of detail is needed. A person responsible for viewing two-dimensional road ledger attached maps must first clarify whether the information they want to confirm can be determined from the plan view or whether other materials are required.

For example, if you want to confirm how far a road area extends, a 2D road ledger map is very useful. If boundary lines and widths are indicated, they provide clues for understanding the relationship between the on-site road right-of-way and adjacent land. The locations of encroachments, the presence or absence of gutters or sidewalks, the position of the road centerline, and the configuration near intersections are also items that are easy to check on a 2D map.

On the other hand, pavement surface settlement, unevenness or steps, poor drainage, structural deterioration, and slope deformations cannot be fully understood from two-dimensional road ledger maps alone. These need to be assessed in combination with site photographs, inspection records, survey data, repair histories, and the like. Even if the drawings appear to show no problems, aging and deformations may have progressed on site.

Also, the information shown on road ledger maps and accompanying maps reflects the road conditions at the time they were created. If construction, repairs, occupation, boundary confirmation, private land development, road improvements, or similar activities have been carried out since then, the maps may not match current conditions. In particular, older drawings may show road alignments and surrounding features that differ from the present situation.

Therefore, when using two-dimensional maps attached to the road ledger, you should not treat the lines and text shown on the drawings as absolute; you need to verify the creation date, update history, surveying accuracy, source materials, and consistency with on-site conditions. To improve the accuracy of road management, it is important to use the plan view information as a foundation and, when necessary, supplement it with on-site inspections and additional surveys.

Points Where Differences Arise in Update Operations

In road ledger update work, if you do not understand the difference between the 2D road ledger attached map and the road ledger map, the scope of work tends to become ambiguous. In particular, when there are road improvement works, area changes, openings for use, decommissioning, realignment, sidewalk improvements, or side-gutter repairs, it is important to clarify which documents to update and to what extent.

Updates to 2D road ledger maps primarily focus on reflecting post-construction road shapes in the plan view. Road boundary lines, centerlines, road widths, structures, side gutters/ditches, sidewalks, slopes, retaining walls, intersection geometries, and annotations are corrected so that the drawings are consistent with the actual conditions when viewed as plans. Sometimes paper drawings are revised, while other times it is necessary to replace PDFs, edit CAD data, or integrate with map data.

When the phrase "updating the road ledger map" is used, it can include not only the supplementary diagrams but also ensuring consistency with records and related ledgers. You may need to verify information beyond the drawings, such as route length and width, changes to areas, the service commencement date, certification information, and management classification. Even if only the lines on the drawings are updated, if the figures in the records and ledger information remain outdated, contradictions will arise during subsequent verification work.

What to pay particular attention to in update work is the discrepancy between the as-built condition on site and the area to be represented on drawings. Even if as-built drawings record details within the construction area, they may differ from the representations required for road register maps. Construction drawings focus on information for carrying out the works, whereas road register maps focus on information for road management. Therefore, rather than simply pasting the as-built drawings, it is necessary to adjust them to align the line types, symbols, notes, map frame, scale, and index required for the register map.

Also, to prevent missed updates, it is important to clarify the flow of construction completion, on-site verification, ledger revisions, updating related documents, approval, and archiving. To ensure traceability even if personnel change, recording the update date, reason for the update, supporting documentation, and the scope of the revisions will make it easier to respond to future inquiries and to reconfirm.

Points to consider when digitizing and integrating with GIS

When digitizing 2D road ledger supplementary maps and road ledger maps, simply scanning paper and storing it may not be sufficient. It is necessary to consider how to create the data from the perspectives of being easy to search, easy to overlay, easy to update, and easy to link with field verification.

Converting paper drawings to PDF reduces storage space and makes viewing and sharing easier. However, simply converting to PDF does not necessarily allow you to accurately edit the lines and text within the drawings. If they are saved as images, it is difficult to handle road boundary lines and centerlines individually, and there are also limitations on searching and measuring. If you plan to continue updating and using 2D road ledger attached drawings, it is desirable to manage separate data for PDF archiving and for editing.

When integrating with map data, alignment is important. Older drawings may have been created as local plans, and overlaying them directly onto modern coordinate systems can produce shifts. You need to align using road centerlines, intersections, public control points, boundary points, and clearly identifiable features, but they may not match perfectly due to the original drawing’s accuracy and distortions.

Also, when overlaying 2D road ledger maps onto a map, it is necessary to clarify what the lines on the drawings represent. If it remains ambiguous whether they are road boundary lines, road centerlines, sidewalk edges, gutter centerlines, or public–private boundaries, people viewing the linked data may misunderstand. In digitization, it is important not only to tidy up the drawings but also to make the meanings of the lines and attributes clear.

Furthermore, digitized road ledger maps have the issue that they are prone to becoming outdated unless update rules are established. In the era of paper drawings it may have been possible to operate with a low update frequency, but once the data are shared electronically within the agency and with stakeholders, there is a risk that outdated data will be used immediately. It is necessary to clearly define management of the latest versions, update histories, the distinction between view-only and editable versions, and the distinction between approved data and data in progress.

Digitization and GIS integration are major means of improving the efficiency of road management. However, if data are created without understanding the meaning of the original two-dimensional maps attached to the road ledger, they may look convenient but their reliability as management documents can decline. It is important to organize and maintain them taking into account the nature of the drawings, their accuracy, and their update history.

How to Connect with On-site Verification

To make practical use of 2D road ledger attachment maps and road ledger maps in actual work, operations that link the drawings with on-site verification are indispensable. In the field of road management, there are things that can be judged from the drawings alone and things that cannot be understood without seeing the site. By combining both, you can improve the accuracy and efficiency of management.

Before conducting on-site checks, organize the target locations using a two-dimensional road ledger map. Confirm route names, positions, intersections, start and end points, carriageway widths, road limits, and surrounding features, and identify in advance the points to be checked on site. Preparing this reduces omissions during field verification. In particular, it is effective to mark on the drawings in advance areas near boundaries, locations of gutters, sidewalk edges, areas around structures, and points where the road limits change.

On site, differences between the plans and actual conditions are checked. Verify whether the side drains shown on the plans exist on site, whether sidewalk widths match, whether intersection shapes have changed, whether there are any structures or plantings within areas presumed to be road right-of-way, and whether there are signs of repairs or improvements. If necessary, take photos and record them together with location information and notes, as this makes them easier to use later for updating plans or explaining to stakeholders.

After the site inspection, organize the items that should be reflected on the drawings. Determine whether the ledger should be updated immediately, whether additional investigation is required, whether cross-checking with past records is necessary, or whether the as-built drawings should be reviewed. It is also important to confirm not simply that the site observations are directly reflected on the drawings, but whether there is evidence to formally update the road ledger.

In such cases, the 2D road ledger-attached map is extremely useful as a base sheet for on-site verification. You can record the positions confirmed in the field on the drawings, making it easier to identify locations that need updating later. There is also a practice of printing them on paper and taking them into the field, but if digitized drawings can be viewed on field terminals, it becomes easier to link them with on-site photos and location information.

In road management, both the accuracy of drawings and the timeliness of field information are important. By linking 2D road ledger maps with on-site inspections, you can transform old drawings from being merely archived into management information that can be used in the field.

Summary: Understanding the differences improves the accuracy of road management

Two-dimensional road ledger-attached maps and road ledger maps are both essential documents for road management. Road ledger maps often refer broadly to drawings related to the road ledger, and it is easier to organize one's understanding by regarding the two-dimensional road ledger-attached map, among these, as a plan view that shows a road's location, boundaries, width, and structures.

In practice, names are not always clearly differentiated. Therefore, instead of judging by words alone, it is important to check what is shown on the drawings, which tasks it will be used for, the extent of the updates, and how it relates to the records and on-site verification.

Especially when advancing digitization and GIS integration, the way two-dimensional road ledger maps are handled has a major impact on the efficiency of road management. By not simply storing them as PDFs but also considering searchability, georeferencing and alignment, attribute management, update histories, and linkage with field inspections, the road ledger becomes a more usable management platform.

In future road management, it will be important to leverage existing two-dimensional road ledger maps while combining them with high-precision positional information, photos, point clouds, and survey results obtained on site. By verifying on site the locations of road areas and structures shown on the drawings and accurately recording sections that need updating, you can reduce rework in ledger updates and more easily prevent misunderstandings among stakeholders.

As a means to streamline such on-site checks, using smartphone-mounted high-precision GNSS positioning devices like LRTK makes it easier to link road ledger maps with on-site location information. If you want to move beyond treating two-dimensional road ledger maps as mere archived drawings and instead verify, record, and use them to support updates in the field, it is worth considering a road management system that incorporates high-precision positioning.