Page 331 - 360.revista de Alta Velocidad - Nº 5

Control and Maintenance of Railways through Satellites.
Is it possible?

2. CosmoSkyMed: constellation formed by 4 satellites, located in synchronous orbits to the
sun. Its resolution in the x-y plane varies between 1 and 5 m and its accuracy in the z-axis
is around cm (Italian Space Agency, 2016).
3. RadarSat-2: Its spatial resolution on the earth's surface varies between 1 and 5 m depending
on the image size captured, while the accuracy that can be achieved in the measurement
of subsidence is 5.6 mm (Canadian Space Agency , 2015).

3.3 Feasibility of using satellites in railway maintenance

In order to study the usability of satellites in maintenance, a comparison has been made of the
measurement ranges of each of the satellite capacities with the measurement ranges used in
railway maintenance.
- High resolution images:
High-resolution images can be used to observe the variation of distances. For this it is necessary
to take into account the highest resolution available in the market today, 25 cm in the horizontal
plane, reachable only by the Worldview-3 satellite. This factor immediately discards the
possibility of measuring path quality parameters located in millimetric ranges. In addition, it
discards the defects of cracks present in sleepers or sleepers, nor the surface defects existing
in the rails. Another element that could not be controlled by the use of satellite images are the
fastenings between rails and sleepers, since their small size discards this possibility. However,
we could control the ballast shoulder, distance between the lane and the beginning of the bank
slope, which can vary between 90 and 110 cm.

On the other hand, high resolution images allow us to observe changes in colour between each
satellite pass. This variation of colour can give us very useful information for the control of
different elements:

• Emergence of vegetation in undesirable areas.

• Detection of areas of surface moisture where it would not be expected, which may
reflect poor drainage or obstruction of gutters.

• Control of the existence of fauna or burrows that can deteriorate or weaken the
embankments of the infrastructure.

• Contamination of the ballast, characterized by a whitish colour produced by the elevation
of the fines of the ballast itself to the surface.

• Existence of obstacles in the access roads.
• Fence perimeter elements and fallen noise attenuation.
• Signalling vertical elements and fallen catenary posts.
• Slopes landslides and landslides.

• Existence of objects in the drainage elements such as ditches or pipes.

- Humidity:

The use of satellites such as SMOS or SMAP in the detection of surface soil moisture in rail
maintenance has been ruled out due to the spatial resolution of these systems, which exceeds
10 km, and prevents the measurement of problems in linear elements such as Drainage of
railway systems. However, it is important to highlight the numerous applications that these
satellites could have if they had their spatial resolution improved.

International Congress on High-speed Rail: Technologies and Long Term Impacts - Ciudad Real (Spain) - 25th anniversary Madrid-Sevilla corridor 329