Topographic Survey

The topographic survey consists of the mapping of the surface of a land, through measurements made by a surveyor, for the elaboration of a topographic plan that marks the variations of the relief and other geographical accidents. It is a fundamental element and is present in the different phases of a construction: in the project, in the execution and in the inspection of the work.

Levantamento Topográfico

What is a topographic survey?

The topographic survey consists of the representation - planimetric or altimetric - in chart or plan of the notable points, as well as the geographical accidents and other details of relief, based on precision measurements (which include optical and GPS equipment) carried out next to a terrain.

There are 3 types of topographic surveys that can be used to measure the elements and characteristics of a terrain: the planimetric, the altimetric and the planialtimetric . The first refers to measurements on a plane, while the second raises measurements vertically. The union of these two results in a planialtimetric survey, a method that allows a more complete mapping:

Planimetric survey

The topographic planimetric survey, also called Planimetry, is characterized by measuring the horizontal projections that define an area .

This type of survey is mainly used to determine the boundaries of a terrain.

Altimetric survey

The elevation survey consists of defining the heights of a terrain . This method can also be called altimetry, and records the degree of slope of a land, such as valleys, hills, slopes, slopes, etc.

Contour lines are plan representations of points on a terrain that have the same height. When connecting them through lines, the level curves are obtained. Thus, the main function of an altimetry is to represent the relief of an area, fundamental information for the representation of the characteristics of a terrain.

The altimetric topographic survey or leveling, consists of a topographic plan with level curves, which represent the variations of the relief, and elements found in it. Contour lines do not take into account houses, walls or other unnatural constructions.

Planialtimetric survey

The planialtimetric survey consists of the union between the planimetric and altimetric surveys . This method allows recording both the measurement of the horizontal projections and the differences in height of the terrain relief. That is, it generates a more complete mapping.

This survey is necessary in cases where a detailed mapping of the conditions of a land is required.

Georeferenced Survey

It is a topographic survey that is accompanied by geographical coordinates.

What does a topographic survey contain?

According to each surveyor, the information may be more or less detailed as well as the type of format delivered (essentially digital but it can even be 3D). Some of the information to be provided will be:

  • Land boundaries (walls, fences, landmarks, etc.);
  • Levels and contour lines showing the terrain's morphology;
  • Location of buildings and neighboring buildings (when they are nearby);
  • Location of infrastructures (water, sanitation, rain, electricity, telephones, gas, etc.) and respective threshold dimensions;
  • Access location (roads, paths, etc.);
  • Location of main tree species (especially if there are protected species, such as the cork oak);
  • Geographic coordinates, if the topographic survey has been contracted with this requirement.

What is a topographic survey for?

The topographic survey aims to map the surface of a land, and compile a set of data that will later be used for the preparation of plans and profiles, graphical representations of the characteristics of the land.

It is an essential element in the elaboration and execution of any construction project , it is essential for the registration of the land in the registry office, to request municipal licensing, for the execution of earthworks or removal of lands, control and execution of the work, inspection works, etc.

In the case of building a house, surveying is usually the first step for the architect to develop an architectural project . Hence, any buyer of a plot of land must request it even before purchasing it. Not only because its realization represents an additional cost, but because in this way it is possible to detect possible non-conformities between the areas registered in the Land Registry or the Land Register and the reality revealed by the topographic survey.

This survey is essential for registering the property in a notary's office, for the municipal licensing of civil construction works and later for the execution of works, such as earthworks or land removal. In brief. Topographic Survey is used to:

  1. Determine the limits and areas of urban and rustic land;
  2. Carry out the altimetric survey in order to provide the designer and the person responsible for the work with data about the elevations and depressions of the terrain;
  3. Facilitate land registration and registration for legal purposes;
  4. Develop road or channel profiles and rivers;
  5. Obtain transversal cuts to volumes, such as terrain elevations and others;
  6. Measure volumes;
  7. Determine the volume of landfills.

Who can perform a topographic survey?

A professional qualified to produce a topographic survey is called a surveyor . It is he who will define the type of topographic survey and make the necessary measurements for its elaboration, using specialized measuring equipment.

In Portugal, topographical technicians must be authorized and certified , in accordance with the law, by the General Directorate of the Territory (DGT) . If you wish, you can consult the updated list of land registry technicians qualified to carry out the activity in the territory of mainland Portugal, containing the contacts and areas of the country where each technician provides services.

You can also use collective entities, public or private ( updated list ), with authorization (permit) for this purpose, which in turn will use the aforementioned land registry technicians.

How much does a surveying cost?

The value of a topographic survey varies with each entity or surveyor, area to be mapped, geometry of the terrain, estimated time, as well as the region of the country.

It is advisable to ask for more than a quote in order to choose the best price / quality ratio. But it is normal to find technicians who charge values in the order of 200 € for a land of 450m2, and between 300 € and 400 € for larger land, up to 1000 m2, but there are those who provide lower budgets.

But the type of surveyor survey can also influence. Here are some reference values (taken from Habitissimo , for a land with an area of 450 m2:

  • Altimetric survey and Planimetric survey - The cost is around 150 €;
  • Plani-altimetrico survey - The cost is about 200 €;
  • Georeferenced Survey - The cost is about 250 €;
Updated on: 
19. February 2021
 
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