Geomatics coherently covers all knowledge and technologies required for the production and processing of digital data which is used to describe territory, resources or any other object or phenomenon with a geographical position.
The word “geomatics” comes from “geo”, which means earth, and “informatics”, which means the automated processing of information.
Geomatics is a diverse and exciting field that uses science and technology to measure the Earth. Geomatics helps to produce maps and plans as well as measurements and information regarding the location of various elements on land such as roads, houses, rivers, etc. It also provides the means to follow persons, vehicles and events on our planet such as natural disasters, epidemics, floods, forest fires, climate change, etc. online and in real-time.
Geomatics is very technological, using Global Navigation Satellite System (GNSS) positioning, geo-spatial databases, the internet, satellite images, 3D terrain models, airborne lasers, measuring instruments on the ground, etc.
Geomatics is also used to demarcate land, establish the boundaries between countries, position roads or major infrastructure and protect the property of citizens. This allows laws and surveying to work together. Whenever you want to know where you are, where you are going, where you can build or where you have to take action on the ground, you will need geomatics. Whether on the global scale or in millimeters, it provides information which is essential to society. Geomatics is the foundation of sustainable development.
Photogrammetry is the science of making measurements from photographs. For this purpose, photography and image processing require special techniques and appropriate hardware and software. The concepts presented in this section apply to any type of shooting (air or land) even if the many of the terms used mostly refer to air.
An image constitutes a flat and distorted capture of the environment. With this alone, it is not possible to obtain the three spatial dimensions. For reconstruction of a 3D model, you need (at least) two images which have been taken from two different points of view and then intersected. This principle is similar to the function of the visual system that allows us to perceive the relief of our surroundings with our two eyes: stereopsis. Two images taken under conditions similar to those of human vision (whose views are parallel but offset in space) form a stereoscopic pair that gives the feeling of depth through stereoscopy.
So that the object is seen on several photographs, one photograph must cross over the other. This is referred to as overlapping. Forward overlap is the overlap between successive photos and side overlap is the overlap between the strips of photos. The concept of overlapping is essential to photogrammetry. It ensures a complete, solid model (without gaps). With drones, the recommended overlap is 80% / 60%. That means 80% forward and 60% side. This allows for 12 different angles for each object and minimizes elevation errors.
The idea is then to restore the geometry of an object from these pictures which are taken from different viewpoints. In order to assemble and connect the pictures to each other, aerial triangulation (AT) is used to create a relationship between the “image” coordinate system and the “object” coordinate system. A manual approach to this step is done with the internal orientation, first relative and then absolute (fulcrum) in the “object” coordinate system where each pair of images is treated separately. Nowadays, thanks to new technology and digitization, all the images are processed together in a block, enabling error compensation (bundle block adjustment). The assembly is based on the execution of a correlation function, i.e. a function that will have special properties when the images are locally similar. A search algorithm of corresponding points (epipolar geometry, reducing to lines) allows the search area to be reduced. This way, correlation or connection points (tie points) may be obtained that allow the construction of the model.
In addition, the input images are geotagged, that is to say, they have approximate coordinates using GPS / IMU data integrated on the drone. This saves time and helps during assembly.
At the end of the process, we obtain 3D models, point clouds or orthophotos.
With the development of digital cameras, photogrammetry has become a fast and accurate technique for collecting geographic data.
With terrestrial photogrammetry, photos are taken from the ground. Anything that is not observable from the sky (facades, interiors, arches…) should be processed by terrestrial tools and methods. Stereoscopy is achieved through a change in position by the photographer or by the combined use of two cameras. It allows to make a survey, study deformations or analyze anomalies. It can also be used in the determination of dimensions and volumes. Currently, terrestrial photogrammetry applications are diverse: reconstruction of facades, heritage conservation (statues, ornaments etc.) as well as small structures etc. It is an excellent addition to specific aerial missions.
With aerial photogrammetry, photos are taken from the air (by drone, aircraft, satellite, etc.) in a round trip flight of the whole mission area. It is used for large areas or when access is difficult or hazardous to an operator. Aerial photogrammetry applications are numerous and diverse: calculating volume measurements, linear calculations, cartography, monitoring structures, exploring hazardous or inaccessible areas, factories, roofing, quarries, agricultural land, etc.
Geographic Information System (GIS)
GIS is an information system capable of creating, transforming, analyzing and storing geographic information. In particular, this enables the creation of maps and plans. There are two types of viewable graphic data in GIS software: raster data and vector data. Raster data consists of images with a matrix of cells (or pixels). This data may be interesting to use, particularly as vectorization support. Indeed, it is possible to create vector data from raster images. In turn, vector data consists of geographic elements located by XY coordinates. There are three types of vector data: points, lines and polygons. Points are used for the representation of punctual symbols such as a municipality on a map, a tree on a parcel, etc.; lines are used to represent roads, rivers, railway tracks, streams, etc.; polygons are used to represent all surface objects such as states and counties on a map or parcels on a municipal map, etc. Vector data deals individually with geographic objects. This data is used principally for creating statistical maps. It makes it possible to customize geographic areas and assign quantitative attributes.
In a GIS, each object is assigned a record containing alphanumeric information, i.e. for storing information describing the objects (name, address, description, history, news…). The contents of these records depend on your specific needs.
There are many fields of application for GIS such as urban planning (land registry, comprehensive development area maps, roads, sewer systems), transport (urban transport planning, route optimization), hydrology, forest (cartography for planning, logging management and forestry) and geology (mineral exploration). There are also various advantages of GIS: storing information clearly and definitively, managing a wide range of object information, understanding phenomena, predicting risks (simulations), rapidly establishing cartography, locating and reacting quickly to events which affect the territory, calculating costs and profits, providing itineraries and creating appropriate plans.
Above all, Hélicéo seeks to provide high precision for drawing and producing different types of maps used to identify territory. These maps can be urban (street maps), topographic (relief of an area), cadastral (breakdown of a territory into land properties), forestry or land use.
Bathymetry employs different techniques for 3D modeling and measuring depths and relief of seabeds, lagoons and streams to determine their underwater topography. The fields of application for bathymetry are diverse: measuring volumes of sand under water and gravel for pits, or determining siltation levels in lakes or lagoons, surveying river beds by creating longitudinal or cross-sectional profiles, or simply, reconnaissance and exploration of river crossings on discovery sites.
Building Information Modeling (BIM)
Building Information Models can be described as “digital files which contain all technical and regulatory data of a structure”. A revolutionary way to describe buildings. A BIM contains all the objects which are components of a building (walls, slabs, windows, doors, openings, stairs, columns, beams, utilities, surroundings, etc.) and their characteristics. All objects of the model are geolocated in space. Technologically speaking, it is a set of standards, tools, methodologies and collaborative platforms. Many relationships between objects can thus be described: wall junction, opening in a wall, etc.
Every professional involved with the building enters data relevant to their task into a unique file that may then be shared (e.g. for surveyors, 3D survey data which has been processed with digital tools) . This “digital model” is built along with the project, allowing for constant visualization of progress and changes. Thus all those involved in a project have a real-time estimate of budgets and deadline. It also avoids the need to enter the same information multiple times, therefore reducing extra costs and errors. This allows you access to 6 dimensions: the three spatial dimensions, the temporal and financial dimensions and the life cycle management dimension. This concept expands to include everything related to the surroundings of the building with the integration of digital terrain models, land records, nearby buildings, topology, etc.