Introduction
The evolution of surveying techniques has reshaped how professionals measure, document, and visualize the built and natural environments. Surveying is essential because a planned building is never exactly the same as the built structure. Differences in construction processes, material behaviors, and site conditions often create discrepancies. Accurate surveying identifies, documents, and corrects these differences when necessary.
From the early days of hand-drawn drafting to the precision offered by modern technologies like LiDAR, each method has influenced its era’s approach to accuracy, efficiency, and representation. This article explores three key surveying methods—drafting drawings, traditional surveying, and LiDAR—to examine their respective strengths, weaknesses, and applications in fields such as architecture, construction, and archaeology.
Drafting Drawings: A Manual Approach
Drafting drawings were traditionally created through a meticulous, manual process, requiring technical skill and precision. Surveyors used basic tools like measuring tapes, compasses, and levels to gather measurements in the field. Once the data was collected, draftsmen translated it into scaled drawings using instruments like rulers, protractors, and T-squares. These hand-drawn plans, elevations, and sections represented the built environment. Later, with the rise of CAD software the drafting moved into the digital era, leaving the surveying behind.
It’s worth mentioning that this method is rarely used today, only for really small projects, because its very time- and labour-consuming, wich makes it also very expensive. The level of accuracy is often compromised by human errors. The margin of error depends on the professional, but is generally not smaller than 5 cm on the horizontal plane, and generally little or no information about inclined surfaces. As a result, the vertical precision is very low.
Laser measurers have to be mentioned here as the more modern version of this approach, which simplifies workflow and human resource need, but has the same disadvantages.
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Traditional Surveying: Total Stations and GNSS Receivers
Setup and Functionality:
Total Stations require precise setup over a point that we either have known coordinates for or coordinates that we will assign using a tripod, prism, and leveling tools. With the help of the surveying prism, we measure a relative distance. Distance alone is not enough to calculate the coordinates of points. A total station requires a baseline measurement that establishes the zero-degree azimuth for the project.
GNSS Receivers rely on satellite positioning to collect data. By using only satellite position, it can give us an accuracy of 3–5 meters, so we need to use a third element to achieve greater accuracy. The control segment, which can be a base station (usually another static GNSS receiver), calculates all the errors and anomalies and sends them to the user’s receiver with RTK corrections. Another control segment can be a local CORS network to which you can connect through NTRIP.
In both cases, setup is fast: typically 5 minutes for the total station and 1–2 minutes for the GNSS receiver.
Data Collection and Accuracy:
Total Stations excel in open environments but struggle when the line of sight to the prism is obstructed by trees or buildings, requiring additional setups and traversing. Accuracy depends on precise setup and maintaining a stable instrument position. If set up correctly, it can provide millimeter-level accuracy, often within 1–2 millimeters under ideal conditions. Total stations require uninterrupted line of sight, are sensitive to setup errors, and depend on relative measurements, making errors cumulative if a point is incorrectly measured. Setup is slower than GNSS, but it compensates in accuracy.
GNSS Receivers work well in open areas but face issues under dense canopies or near tall structures where satellite signals may be blocked. Advanced models incorporate imaging for data collection in obstructed areas and offer centimeter-level accuracy (about 2–5 cm) when using RTK corrections. Their accuracy decreases in environments with limited satellite visibility, making them less effective in forested or urban environments with signal obstructions. GNSS receivers generally provide faster data collection due to easier setup and flexibility, allowing free movement without line-of-sight constraints.
Both instruments work for open areas but struggle with indoor spaces, where neither is fast or accurate.
GNSS receivers and total stations are essential tools for placing measurements within a defined coordinate system, ensuring spatial accuracy and alignment with existing geospatial frameworks. GNSS receivers provide precise geographic coordinates based on satellite signals, allowing for accurate positioning in global coordinate systems such as WGS84 or other regional datums. Total stations, on the other hand, achieve high-precision measurements within local coordinate systems by referencing known benchmarks or control points. Together, these tools enable surveyors to integrate their measurements seamlessly into broader projects, ensuring that all data aligns with architectural plans, cadastral boundaries, or infrastructure networks. Without these instruments, achieving accurate georeferencing and spatial consistency in professional surveying would be nearly impossible.
LiDAR Surveying: Revolutionizing Precision and Speed
LiDAR (Light Detection and Ranging) uses laser pulses to measure distances with high precision. It creates a dense 3D point cloud that captures all details in the scanner’s range, such as topography, structures, and vegetation. These are processed into 3D models or digital elevation models (DEMs), making LiDAR essential for architectural surveys, topographic surveys, infrastructure planning, and archaeological exploration.
LiDAR surpasses manual and traditional methods with exceptional accuracy, speed, and versatility. It provides millimeter-level accuracy, collecting millions of data points in seconds, reducing time for large-scale surveys. It does not rely on satellites, working well in areas with obstructed skies, such as forests, urban environments, and even indoor spaces witch makes it invaluable for architectural documentation, building inspections, and construction monitoring. Additionally, LiDAR creates highly detailed 3D models with rich data, capturing intricate features of both built and natural environments. This combination of precision, speed, and adaptability makes LiDAR the most advanced surveying method available today.
LiDAR in Action: Advanced Applications and Specific Considerations
LiDAR’s ability to capture vast amounts of data quickly makes it ideal for large-scale projects and environments where traditional surveying methods fall short. For example, in dense forest environments, LiDAR can map the ground surface beneath the trees, providing valuable data for forestry and environmental monitoring.
Additionally, specialized versions of LiDAR, like bathymetric LiDAR, allow for underwater surveys, using green-wavelength lasers to penetrate water, enabling surveys of shallow coastal areas, rivers, and lakes.
However, challenges remain. LiDAR’s ability to capture data on highly reflective surfaces, such as glass, or very dark objects may be limited, which could cause data gaps or distortions. While excellent for topographic mapping, its effectiveness decreases in dense canopies or turbid waters. But compared to the other two survey methods, LiDAR achieves millimeter accuracy on vertical or inclined surfaces also. It can slo capture much more detail, than any other survey method.
Mixed Techniques
Combining LiDAR with GNSS receivers or total stations is a powerful approach for positioning a point cloud within an existing coordinate system. While LiDAR excels at capturing detailed 3D data of the environment, it operates relative to its own scanning location and requires additional georeferencing for integration with broader spatial frameworks. By pairing LiDAR with a GNSS receiver, precise geographical coordinates can be obtained, allowing the point cloud to be anchored to global coordinate systems. Similarly, using a total station ensures millimeter-level accuracy when aligning the point cloud to local grids or predefined reference points. This combination maximizes both accuracy and spatial consistency, making it the ideal solution for projects that demand precise integration of scanned data into existing architectural plans, infrastructure networks, or geospatial models.
Conclusion: Embracing the Future of Surveying
LiDAR stands out as the superior solution for modern surveying needs. Its ability to capture vast amounts of highly detailed and accurate 3D data in a fraction of the time, combined with its versatility to survey complex interiors and challenging environments, makes it an unparalleled choice. Furthermore, when integrated with GNSS or total stations, LiDAR can seamlessly position its rich point cloud data within existing coordinate systems, offering both precision and compatibility. As projects grow increasingly complex and demand higher levels of detail and efficiency, LiDAR emerges as the ultimate surveying technology, redefining the standards for accuracy, speed, and data richness in the field.
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