GB/T 41452-2022Technical code of practice for three-dimensional model production based on vehicle-borne mobile mapping (English PDF)

3.1 Vehicle-borne mobile mapping system

On the vehicle-borne platform, a comprehensive mapping system consists of integrating control system, positioning and attitude mapping system and one or more other mapping sensors (laser scanner, digital camera, video camera, etc.). [SOURCE: CH/T 6004-2016, 3.4]

3.2 Vehicle-borne mobile mapping

A mapping method for obtaining data such as ground object point clouds and images with geospatial location information by using the vehicle-borne mobile mapping system (3.1).

3.3 Three-dimensional continuous surface model

A ground object continuous triangulated irregular network structural model that is measurable and with textured information, and that is made by data such as using point clouds and images, etc.

3.4 Three-dimensional entity model

A ground object entity three-dimensional model that is measurable and with textured information, and that is made by using data such as point clouds and images, etc.

5.1 Space-time datum

5.1.1 Plane coordinate system

The plane coordinate system should adopt CGCS2000. If other plane coordinate systems are used, they shall be linked with CGCS2000.

5.1.2 Elevation datum

The elevation datum should adopt the 1985 national elevation datum. If other elevation datums are used, they should be linked with the 1985 national elevation datum.

6.1 Data acquisition and analysis

model, orthophoto map, topographic map, administrative division map, traffic map, etc.;

d) other relevant data.

6.2 On-site reconnaissance

The on-site reconnaissance should comply with the following regulations:

a) on-the-spot understanding of the natural geography, humanities and traffic conditions of the operating area;

b) understand the authenticity and availability of existing data;

c) reasonably plan the driving route and the erection position of the reference station.

6.3 Preparation of instrument

Vehicle-borne mobile mapping equipment shall be used within the validity period of metrological verification or calibration; and shall be in normal working condition. Instruments and equipment shall comply with the provisions of 5.3 in CH/T 6004-2016.

7.1 Design principles and contents

The preparation of the technical design document shall comply with the provisions of CH/T 1004; and the main contents shall include project overview, survey area overview, existing data, reference documents and operation basis, overall task requirements and operation flow.

7.2 Project overview

It shall instruct the source of the project, the purpose of the task, the scope of the project, the workload and the duration.

7.3 Survey area overview

It shall instruct the natural and geographical conditions of the survey area related to the design plan or operation as required; and the content should include the topographical overview, landform features, climate conditions, and traffic conditions of the operation area. If necessary, the relevant surveying and mapping data of the survey area shall be collected.

7.4 Existing data

It shall instruct the quantity, form, quality condition and availability of the existing data.

7.5 Reference documents and operation basis

It shall instruct the referenced standards, specifications and other technical documents.

7.6 General requirements of task

It shall instruct the used space-time datum, the quality requirements for point clouds, images and three-dimensional models.

7.7 Operation flow

The operation flow shall include the following contents:

a) Inspection requirements for vehicle-borne mobile mapping equipment;

b) Collection route planning, including collection time and route;

c) Control mapping, including the distribution and mapping requirements for ground control points;

d) Data acquisition and preprocessing, including the acquisition and preprocessing requirements for positioning and attitude measuring data, image data and point cloud data;

e) production of results, including the production of three-dimensional continuous surface models and three-dimensional entity models;

f) Quality inspection of results, including the content and specific requirements of quality inspection.

8.1 General

When acquiring data, it shall meet the following requirements:

a) Comply with the traffic rules; drive according to the designed route; control the driving speed according to the actual needs and system limitations; and set the laser emission parameters and camera shooting parameters;

b) Monitor the operation of the equipment and the data recording; and record the abnormal situation in time;

c) The road sections that are severely blocked or cannot be entered by vehicles shall be recorded in time; […]

8.4 Control mapping

The specific layout is as follows.

a) If there are special (superior) requirements for accuracy, signs shall be laid along the line in advance and the mapping shall be carried out according to the requirements of the corresponding accuracy level. the spacing between the control points is 100m~1000m.

b) For non-superior requirements, when the GNSS signal is poor and cannot meet the operation accuracy requirements, other high-precision mapping methods (such as GNSS RTK mapping, total station mapping, level gauge mapping, etc.) should be used to lay out along the scanning trajectory in the survey area and measure the control points.

8.5 Data acquisition

The specific requirements for data acquisition are as follows:

a) Data acquisition from GNSS reference station shall comply with the provisions of 6.4 in CH/T 6004-2016;

b) Data acquisition from the positioning and attitude measuring data shall comply with the provisions of 6.5 in CH/T 6004-2016;

c) Image data acquisition shall comply with the provisions of 6.6 in CH/T 6004-2016;

d) The point cloud data collection shall comply with the provisions of 6.8 in CH/T 6004-2016.

8.6 Field data check

After the mapping is completed, the vehicle-borne mobile mapping data is checked to ensure the integrity and correspondence of the positioning and attitude measuring data, image data and point cloud data, as follows.

a) Data validity check. Simple and fast processing of data to check whether the data is valid.

b) Integrity check. Check whether the acquired data is complete, and perform supplementary mapping for areas with severe dynamic occlusion.

c) Preliminary accuracy check. The data accuracy is preliminarily checked by the track quality; and the areas with poor accuracy are marked. If changing the driving path can improve the accuracy, the path shall be changed and re-acquired.

8.7 Data preprocessing

The specific requirements for data preprocessing are as follows:

a) The preprocessing of positioning and attitude measuring data shall comply with the provisions of 7.1 in CH/T 6004-2016;

b) The preprocessing of image data shall comply with the provisions of 7.2 in CH/T 6004-2016;

c) The preprocessing of point cloud data shall comply with the provisions of 7.5 in CH/T 6004-2016.

9.1 Production of three-dimensional continuous surface model

9.1.1 Modeling content

The modeling content of the three-dimensional continuous surface model includes the ground objects such as road, ancillary facilities that are acquired by the vehicle-borne mobile mapping system.

9.1.2 Model making

The making of three-dimensional continuous surface models shall meet the following requirements:

a) The model is composed of TIN and texture, reflecting the features of the structure and texture of the ground objects;

b) The model performs TIN structure modeling based on point cloud data, and conducts the texture mapping based on image data.

9.1.3 Modeling methods

The topological relationship between point clouds is established, and the vehicle-borne synchronization image is used as the texture for automatic mesh construction and mapping, and appropriate editing is performed. The following requirements shall be met.

a) Level-I three-dimensional continuous surface model:

1) Accurately reflect the structural characteristics of roads and auxiliary facilities;

2) The texture details are clear, accurately reflect the characteristics of ground objects; and clearly reflect the difference and separation of different textures;

3) Structural editing is performed on the three-dimensional continuous surface model with the existing phenomena such as suspension, loopholes, adhesions, and stipple, and the model shall accurately reflect the structural characteristics of the ground objects.

b) Level-II three-dimensional continuous surface model:

2) The base contour shall be extracted from the point cloud data; and the model height should be automatically matched or manually interpreted based on the point cloud data;

3) The texture should have clear details, accurately reflect the features of the ground object; and the difference and separation of different textures should be clearly reflected.

9.2 Production of three-dimensional entity model

b) Level-II road model:

1) It shall basically reflect the structural features of the road model; and three-dimensional geometric modeling shall be carried out for structural features exceeding 1m;

2) The base contour shall be extracted from the point cloud data; and the model height should be automatically matched or manually interpreted based on the point cloud data;

3) The texture shall reflect the road material and traffic markings.

9.2.2 Model of auxiliary facilities

9.2.2.1 Modeling content

The ancillary facility model contains the following:

a) Road traffic type, including kilometer piles, warning piles, anti-collision buckets, parking facilities, traffic sign facilities, bus stop booths, taxi waiting point board, sign board, cameras, signal lights, guardrails, cement separation belts, metal separation belts, toll booths, etc.;

b) Public facilities type, including water, electricity, gas, heat and other inspection manhole covers, street lights and related facilities;

c) City appearance and environment type, including trash cans, advertising plaques, propaganda boards, etc.;

d) Other types.

9.2.2.2 Model making

Ancillary facility model making complies with the following provisions:

a) The geographic location of the ancillary facility model shall be determined based on the acquired point cloud data;

b) The texture information of the auxiliary facility model should be determined based on the acquired image data;

c) The bottom of the auxiliary facility model shall be consistent with the road model.

9.2.2.3 Modeling methods

The structure lines are extracted based on the point cloud data; and the modeling is carried out by means of automation or human-computer interaction. Modeling can also be done symbolically. The modeling of ancillary facility model shall comply with the following provisions:

a) Model of primary ancillary facilities:

1) It shall accurately reflect the geometric structure and detailed characteristics of the ground objects;

2) Surface models such as cement separation belts and metal separation belts should be lofted and modeled based on extraction structural lines of point cloud data;

3) Models such as traffic signs, road nameplates, signs, advertising plaques, and propaganda boards should be modeled based on extraction structure line of point cloud data; and textures should be made by using the acquired image data;

4) Point models such as kilometer piles, warning piles, anti-collision buckets, parking facilities, traffic sign facilities, cameras, and signal lights should be represented by different preset symbols according to their types.

b) Model of secondary ancillary facilities:

1) For the same type of ancillary facilities, a general model should be established based on image data, which can reflect the shape and characteristics of ground objects;

2) The details of the model should be appropriately selected according to the actual situation, and texture should be used.

9.2.3 Production of other models

9.2.3.1 Modeling content

Other models mainly include models other than roads and auxiliary facilities that can be acquired from roads, including the following:

a) Buildings (structures) on the ground;

b) Vegetation;

c) Others.

12.1 Requirements for submission of results

The submission of results shall meet the following requirements:

a) The technical documents are complete and intact; the content is true; and the expression is accurate;

b) Operation records, technical data and achievement data are complete.

12.2 Contents of submission of results

The contents of submission of results shall include: […]