Metric survey is a vital issue for all of those who work in fields such as architecture, civil engineering, geodesy and building science. It is the process of collection, analysis and representation of spatial data and measurements of objects, lands or whole structures. The main goal is to supply detailed information about the physical characteristic of an element allowing to create projects, carry out remodeling or conservative action in a precise and responsible way. This kind of work is crucial in different sectors: from the production of cadastral data to the control of structural deformation or to the creation of new buildings and infrastructures.
In the field of construction, for example, metric survey is vital to ensure that the different phases of planning and construction are properly carried out avoiding errors in the creation of plans as well as to ensure that spaces are safe for those who will use them. In the field of architecture it is crucial to collect data about the current condition of the existing buildings and to plan the restoration of historical monuments in a scientific and rigorous way. Similarly, in archeology or in the scientific research field, metric survey offers an essential data base to study exhibits and ancient structures, preserving memory and allowing analysis and comparison over time.
In this article we will focus in detail on what metric survey is, what the most common techniques are and the main application fields.
What metric survey is
Metric survey refers to all operations that aim at measuring and representing the physical reality of an object or area in a precise and scalable way. It is a practice based on geometric and mathematical principles, the accuracy of which depends very much on the quality and precision of the instruments used. The objective is to obtain a faithful reproduction of the form, size, position and physical characteristics of what is analyzed so that the collected data can be used for many purposes: planning, restoration/renovation, conservation, study, monitoring, analysis of stability and so on.
Historical context of metric survey
The metric survey among Egyptians and Babylonians
The earliest forms of metric survey date back to ancient civilizations, such as the Egyptians and the Babylonians, who used rudimentary measuring methods to draw boundaries and build monuments. One must only consider the Egyptian pyramids or Roman aqueducts to understand the high degree of technical expertise already reached in distant times.
Metric survey in the Renaissance
Over time metric survey has developed keeping pace with technological progress. In the renaissance, thanks to figures like Leon Battista Alberti and Leonardo da Vinci, metric survey improved as did graphic representation. Perspective, the use of optical instruments and new geometric and trigonometric notions contribute to make metric survey significantly more accurate.
Metric survey in the 19th Century until now
During the 19th and the 20th Century thanks to the invention of new instruments like theodolites and the EODM (Electro Optical Distance Measurement) metric survey became increasingly more precise. Later, the development of electronics and informatics revolutionized this sector: Today we can use scanning lasers, high-precision GPS and advanced software for data processing and 3D modeling that allow transforming data into extremely detailed digital models.
Techniques of metric survey
Over time the techniques of land and metric survey have become numerous and more accurate offering today different solutions according to the type of projects and the precision level needed. Let’s analyze some of the most used methods using images and diagrams to have a better understanding of the functioning principles.
1. Direct survey
This is the most traditional method in which measurements are carried out manually with basic instruments such as measuring tape, level, triangle, goniometer and measuring wheel. This basic technique is currently used for small metric surveys where there is no need for high precision or when more sophisticated tools are not available.
o Advantages: easy to use, reduced costs, immediate.
o Disadvantages: low precision, higher probability of making mistakes.
2. Land survey with theodolite or total station
Theodolite and total station (that combines theodolite and EODM) are traditional instruments to carry out angle and linear measurements in a very accurate way. They allow collecting data about a land or a structure calculating the position in local or global coordinates. Total station sends out a laser beam that, bouncing on a prism, returns to the device. This allows calculating the distance between the device and the prism according to the time it takes the laser beam to return to the device.
o Advantages: good accuracy, versatility, many possible applications.
o Disadvantages: measuring in complex spaces takes a lot of time, high level of technical knowhow and skills is required.
3. Metric survey with GPS and GNSS
The use of GPS (Global Positioning System) and more generally of the GNSS (Global Navigation Satellite System) has become the most used system for survey. Thanks to this technology it is possible to precisely geo-localize the points of interest combining the collected data with the official cartographic coordinates. The precision of professional GPS systems, also called RKT (Real Time Kinematic) can be very high and have an accuracy of a few centimeters or even millimeters according to the condition regarding the reception of the signal.
o Advantages: very quick, coverage of vast areas, direct integration with digital maps
o Disadvantages: reliance on good weather and no environmental obstacles (like high buildings, thick vegetation etc.) as well as a stable satellite signal
4. Terrestrial laser scanning
Terrestrial laser scanning is a latest generation tool that uses a laser beam to acquire thousands or millions of point clouds very quickly, allowing to reproduce an object or a landscape very accurately. It is very often used in architecture, civil engineering, monument restoration and infrastructure monitoring. The result is a very high resolution 3D model, from which it is possible to create measurements, sections, plants and any other graphic representation.
o Advantages: very high precision, fast acquisition, complete 3D reproduction
o Disadvantages: High cost of the device, complex data processing, need of specialized software
5. Digital photogrammetry and UAV (Drones)
Digital photogrammetry is a technique that allows extracting measurements and 3D models from photos. If, in the past, it was necessary to use special metric cameras, today it is possible to use normal high resolution cameras provided that certain acquiring and calibrating parameters are respected. The use of UAV (drones) with cameras makes this method even more versatile allowing the acquisition of data of vast areas or structures particularly complex to reach by land.
o Advantages: versatile tool, not too expensive, possibility to acquire high quality images from different angles.
o Disadvantages: the need to properly plan flight paths, software to process very complex images and good weather
Each of these techniques can be combined or used in different stages of a project according to specific user needs. For example, on a very big construction site, land survey with total station and terrestrial laser scanning can often be used in combination in order to reach sites that are not easily accessible, and drones to create an aerial mapping as well as very detailed models.
Application of metric survey
Metric survey is used in several contexts because it can provide accurate and reliable data on the geometric characteristics of an environment or object. Here are some concrete examples.
Architecture and restoration
In the architectural field, metric survey is vital to carry out projects that correspond to the construction reality, avoiding mistakes regarding size or proportions. When it comes to remodeling existing buildings, it is crucial to have detailed surveys to understand the actual current condition: walls that are out of plumb, irregularities in the foundations or uneven walls. When it comes to remodeling historical or artistic monuments, metric survey plays an even more crucial role. For example, laser scanning is often used to carry out surveys of monuments, churches, very old buildings to collect data on their state of conservation, plan targeted and non-invasive restoration measures.
Civil engineering and infrastructures
In the field of civil engineering it is customary to carry out land and metric surveys before starting the construction of roads, bridges, dams or other large-scale works. The collected data provide the design team with the information they need to assess the shape of the ground, calculate ground movements, slopes, differences in height and set the correct measurements of a project. In addition, once the work has been completed, the metric survey serves to draw up the as-built documentation, which is essential for future assessments or maintenance operations.
Geodesy and cartography
Geodesy studies the shape and the dimensions of the earth and it is based on extremely precise measurements. GPS and other satellite technologies have allowed to determine with extreme accuracy the geographical coordinates of points distributed all over the planet. These data are the basis of modern cartography both in paper format and above all in digital format. Maps, Geographic Information System (GIS) and road navigation systems are based on complex geodetic networks defined by metrically rigorous surveying procedures.
Archeology and cultural heritage
In the archeological field metric survey allows mapping sites and exhibits accurately, making the study of spatial relations among different structures and their transformation over time easier. The 3D reproduction based on photogrammetry and laser scanning can create realistic images of ancient ruins allowing researchers to study stratigraphies and to make research results more widely known to the public at large.
Technical assessment and cadastral data
Metric survey is often requested to carry out technical assessments in case of disputes related to land borders, tax assessments, real estate assessments or judicial investigations. In these cases the precision of measurements and the clarity of drawings resulting from the assessment are legally relevant. Professionals such as surveyors, engineers, architects and other surveying technicians, have therefore to follow rigorous procedures and certificate the accuracy of the collected data. In the same way, updated land register data and updated real estate plans need metric survey to ensure that physical reality corresponds to official registers.
Monitoring and assessing deformations
Another particularly relevant application of metric survey is the monitoring and assessing of deformations in structures or natural areas in which caves can occur. Through periodic survey it is possible to determine whether and how a building, a bridge or a slope is moving. This plays a crucial role in avoiding risks and schedule targeted maintenance action.
Historical relevance of metric survey
The historical relevance of metric survey is proven by centuries of technological evolution and improvement. If in the past it was a discipline practiced by a few experts, today it has become accessible even to those who do not own expensive equipment, thanks to the spread of software and devices that are increasingly user-friendly. However, the basic principle remains the same: to know in an objective and precise way the space that surrounds us. It is precisely this need for objectification that has led peoples and civilizations to develop increasingly accurate measurement methods, laying the foundations for much of the scientific, artistic and technological achievements.
Metric survey is much more than a simple group of techniques to measure and represent physical reality: it is the basic prerequisite for any design intervention, conservation or study related to the transformation and knowledge of the buildings, infrastructures and natural environment. From modern buildings to historical monuments to be protected, from civil infrastructures to archaeological investigations, this discipline is the key to acquiring accurate information and turning it into a solid basis on which to plan and make decisions.
However, the importance of metric survey is not limited to the present: it also plays an essential role in safeguarding our cultural heritage and understanding history. Thanks to it, we can document the current state of monuments and sites of historical interest, prevent their deterioration and plan restoration operations respecting the artistic and cultural value of the assets. At the same time, it is an effective tool for monitoring the evolution of natural and man-made environments, enabling researchers to better understand spatial dynamics and predict possible risk phenomena.
For professionals - surveyors, engineers, architects, technicians - acquiring skills in the field of metric survey means investing in an essential skill, able to enrich their professional background and guarantee excellence in each project. For students or those who would like to approach this subject, it is an opportunity to get in touch with a constantly evolving discipline, where technological innovations - from laser scanners to GPS and UAV systems - open up increasingly interesting perspectives.
If you are looking for professional support, please contact technical offices or companies specialized in topographic surveying and 3D modeling services, to obtain reliable data and analysis for your project. Remember, an accurate metric survey is the basis on which to build any successful intervention. Investing at this stage means laying a solid foundation for the future.
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