Geometry In Motion [GIM]

Albatroz Engineering adapted its 3D modeling tools to diverse applications. While the primary application is inspection of over-head power lines by helicopter (PLMI) or on the ground (GMI), it is possible to design custom built solutions for many different needs.

The fundamental working principles are common to all applications:

1. A LiDAR sensor acquires the geometry of the scenario by sweeping surrounding objects with a laser beam that measures distance from the emitter to the object. The beam sweeps a planar circular section centred on the sensor.The measurements taken are represented in a polar reference centred on the LiDAR sensor.
2. A vide camera to acquire images of texture and context of the scenario.
3. A vehicle or motorised platform whose motion drives the sensor from one position to the other. In this way, the sequence of planar sweeps in two dimensions fills a three dimension volume.
4. An auxiliary sensor to measure the displacement of the vehicle or the platform: it could be a GPS receiver for outdoor reconstruction or a sfhat encoder, an odometer or another LiDAR

One of the most interesting applications of Geometry In Motion GIM] is the production of virtual models of heritage sites. And there are many more applications:

Frequently Asked Questions [FAQ]

1. How does GIM compare to other 3D modeling technologies?
2. What's the purpose of the image?
3. How fast can GIM travel while modeling?
4. What's the resolution of the 3D models? And the density of points per square meter?
5. Can GIM be used indoors too?

1. How does GIM compare to other 3D modeling technologies?

The most common solutions for three dimension (3D) reconstruction and modeling of outdoor environments uses high quality-high cost equipments designed for survey, architecture, reverse engineering and other high precision applications. The key equation to this activity is the following

LiDAR + GPS = 3D Model

One of the characteristics of these solutions is the long and thorough calibration of localisation and orientation of equipments that must preced data acquisition, which may also take long. As a consequence, the number of acquisition points is reduced to a minimum.

By mounting the sensor system in a vehicle or in a mobile platform, there is a significant reduction on the model accuracy. On the other hand, one gains in flexibility, speed of aquisition and access to new viewpoints. Moreover, the equipment and the operation procedures are less demanding since modeling algorithms acommodate larger measurement errors.

Albatroz Engineering identified the opportunity for competitive 3D modeling applications for outdoor scenarios or installations from mobile platforms.

2. What's the purpose of the image?

Image is not part of the key equation shown above but it is very useful to improve the likelihood of 3D models and to help inexperienced users to recognise the original environments when looking at 3D models. That's why Albatroz Engineering prefers the equation:

LiDAR + Image + Motion + GPS = GIM = Textured 3D Model

3. How fast can GIM travel while modeling?

Acquisition speed depends on the application. The Roman Galleries of Lisbon were modeled at a speed of a few centimeters per second while railway models were created at160kmph (44,4m/s or 106mph).

4. What's the resolution of the 3D models? And the density of points per square meter?

Again, it depends on the application. Albatroz Engineering dispões de equipamentos e sensores de diferentes especificações e faz o software de medição e modelação para todos eles. Por esse motivo, está capacitada para criar uma solução à medida de cada problema.

5. Can GIM be used indoors too?

Yes.

While the system was designed for outdoors and big size scenarios, some modeling devices can be mounted on a aluminum mono-rail and used in confined environments. Such is the case of the Roman Galleries of Lisbon that are about 2,2m wide and 2,5m high. In some sections, height above ground is less than 1m.

Land survey and maintenance of clear ways

It is necessary to monitor the sideways along roads, railways and riversides to detect early any land slides, rock movement, measure the growth of vegetation, etc..

An example of such an application was performed in collaboration with the University of Huelva for ADIF - the Administration for the Railway Infrastructure in Spain, as described in the publication

Prototipo para la Monitorización de la Infraestructura Ferroviaria utilizando Sensores Lidar, Imagen de Video y GPS: Primeros Resultados

(to learn more ) and shown on the right.

High-speed railway inspection in Spain

Computation of irregular volumes

In quarries, landfills and other large sites it is often necessary to determine the volume of the outstanding mass, or, equivalently, the volume that was removed.

On the right there is an illustration of this method to measure the volume of limestone removed form a quarry..

Airborne three-dimension models

The 3D models generated from aircraft are an extension of the 3D models generated from a ground vehicle. Since aircraft move in three dimenstions, the basic model "equation" turns in to:

LiDAR + (GPS+ Inertial Navigation System) = 3D Model

The Inertial Navigation System [INS] yields estimates of orientation (angles) and accelerations along the three motion axes. A video camera can be useful in some applications, in particular if the application requires the integration with airborne photography or airborne survey.

The first example shows quick land survey done in Brasil. Images show how the digital terrain model based on LiDAR data sumperimposes with a GIS model.

Three dimensional model of a section of land with a transmission line and nearby vegetation

The second example was computed automatically from data acquired flying over a forest of eucalyptus, cork oak and pines at speed ranging from 15kt to 40kt (28km/h to 74km/h or 19mph to 49mph).

Scales are shown in meters. The altitude ranges were multiplied by five (x 5) to improve perception of altitude variation above mean sea level. On the animanted model (WMV (575KB) or AVI (668Kb)), altitude is represented in equal proportions to the other dimensions (1:1:1).

Ground altitude and vegetation profile of pines, cork oak and eucalyptus along the Tagus Valley, Portugal

Old memories

The models shown below were the first ones created by Albatroz Engineering in the early days of the company. Together with the LISPOLIS model (the site of the first office in Lisbon), they are the memory of the early solutions, superseded today in quality and features and no loger represent the state of the art of Geometry in Motion [GIM]. They are shown as a memory to old solutions

Juntamente com o modelo do LISPOLIS (o local do primeiro escritório em Lisboa), são a memória das primeiras soluções, hoje superadas em qualidade e funcionalidades e já não representam o estado da arte da reconstrução tridimensional. Apresentam-se aqui em memória das soluções antigas.

The two bridge models below date from May 2006 and were computed automatically from data acquired by car crossing the bridges at typical road velocities (80km/h, 50 mph).

Marechal Carmona Bridge - Vila Franca de Xira, Portugal

3D animated model: GIF [493kb], AVI [470kb]

Vasco da Gama Bridge - Lisboa, Portugal

3D animated model: GIF [439kb], AVI [392kb]

LISPOLIS 3D model

With Albatroz Engineering solutions, it is possible to obtain detailed 3D models in a short notice with a very interesting quality to cost ratio. In case you have a scenario you need to model in 3D, please contact us.