Mobile Mapping System for Cadastral Surveying

Cadastral surveying is quite an important task for all the countries and the governments. The cadastre records the detail location, coordinates, ownership, and a lot a valuable information, which means the location should be very precise. Based on the surveying technology, we are able to acquire the high-precision coordinates in a very reliable and efficient way. MMS (Mobile Mapping System) is one of the latest surveying technology to measure the object by millions of points per second with centimeter accuracy. This article introduces the application of MMS which been used in cadastral surveying, as well as the benefit and detail procedures.

Background: Mobile Mapping Systems for Cadastral Surveying

Cadastral surveying is land management’s most basic function, it can be applied across all the surfaces, gather all sorts of data needed for land management. With the help of both hardware and software, it can deliver location, mapping, distance in different types of formats.
At the moment, the most conventional method of Cadastral surveying is using the Total Stations and RTK GPS, it is time-consuming and inefficient in terms of human productivity. The end results of the traditional method are in 2D, whereas the new age is 3D. 3D data opens up to more possibilities and applications, providing a better platform for land management. LiDar is the latest method for 3D data collection, it achieves better data accuracy and higher proficiency, showcasing 3D data collection at its best.

Figure 1 Traditional cadastral surveying

What is LiDar?

LiDar stands for Light Detection and Ranging. It is an integration of GPS, IMU (Inertial Measurement Unit) and laser scanner, into one system. It achieves a more accurate 3D data with the IMU and GPS input. The main idea behind LiDar technology is, the scanner head emit lasers out, it gets reflected back into the scanner head. Once the system receives the reflected lasers, the location, distance ,and angular measurements are calculated in the span of milliseconds.

Figure 2 MMS components

MMS is one of the methods that use LiDar technology. With the integration of spherical camera into the system, it can provide geo-coded images with the mass point cloud.
Installed on various types of vehicles, it scans and takes pictures while the car moves around the specific area, providing millions of points with distance, location and angular measurements to each individual point. And the point cloud can be applied for 3D modeling, Topographic landscape, Map street view and many other GIS applications.

1. Comparison of conventional surveying method and MMS method

We did a comparison work on both conventional surveying method and MMS method in a small town in Guangxi province, China. Using the conventional way of RTK GPS and MMS, concluding the results as follows;

a) By GPS RTK Receiver
It takes 20 days to finish the whole surveying works in the field, and more than
10 days for drawing and generate the result, totally is 30 days.
The workflow of RTK GPS is very generic and well understood by many, so it will not be illustrated in this article.

b) By Mobile mapping system
Below figure 3 illustrates the workflow of MMS method.

Figure 3 MMS workflow

a) Route Planning

Route planning is essential as a first step, as different areas have different landscapes. A proper planning beforehand will decide what type of vehicle to be used, the sequence of the route to be taken, so the data will be collected in the most efficient way.
Figure 4 shows the route planning, with red circles indicating areas not accessible by car, therefore have to use a motorbike for the scans.

Figure 4 Route planning

b) Field Work

On the field, simplified software is used to manage the work, all sorts of information like the pictures, point cloud data and position will be stored automatically as well as the tracks shown on the handheld device. On the interface, you can check back on the area you have covered refer to the background Map, to ensure the work is in accordance with the plan.

Figure 5 Field data collecting

c) Post Processing
After the completion of fieldwork, the collected data will be processed with compatible software, integrate all the data like location coordinates, distances into numeric formats, virtual displays of real-life visuals.With a specific software for cadastral drawing, the point cloud data can be used for generating cadastral data automatically.

Figure 6 Point cloud and cadastre

In short, MMS method is much faster than RTK receivers in capturing the data on the field, it only takes 1 ~2 days to finish the field work and 5 more days to process the point cloud data. The output results are in 3D compared to the 2D by RTK, a shorter time taken, a more in-depth result. in short, MMS is the next to get method of Cadastral Surveying.

Figure 7 Efficiency comparison between RTK and MMS

2. Conclusion

a) Cadastral surveying requires centimeter accuracy and MMS perfectly meet the needs.
b) The efficiency of MMS relieves the manpower workload, achieving better productivity per headcount.
c) MMS not only serves the purpose of Cadastral Survey, it can also be used for GIS and many other purposes.

BIOGRAPHICAL NOTES

Stefan Wei
Marketing Director in Hi-Target for more than 2 years, he was The Leader of Hi-Target After Sale Department for more than 4 years, and now is the head of product managers team. He has rich experiences in land survey, GIS data collecting and 3D laser solution promotion, support and marketing.

Product Manager in Hi-Target on Laser Scanner products specialized in land survey solution and marketing.
Seven Zhao