Accurate and cost-effective preliminary design study with satellite imagery and elevation models

Systra, specialists in engineering for urban and rail transportation, delivers more accurate and cost-effective preliminary study for railway design using terrain elevation models and satellite imagery alongside conventional civil engineering tools.

Civil engineering: transportation infrastructure

Civil engineering in the transportation infrastructure sector combines the specialist expertise and technologies needed for the planning, construction, operation and rehabilitation of rail and road networks.

Prior to the construction phase, civil engineers must determine the best route, calculate the cubic volumes of earth to be excavated and/or filled in, locate structures and evaluate costs.

Engineers begin the preliminary design study by collecting geographic information. This must be rapidly available, up to date, consistent across vast areas and precise to allow evaluation of costs and planning of site operations.

Systra requirements for a rail project in Algeria

In December 2005, SNTF (Algeria’s national rail transport operator) issued a request for proposals for the development of a 800 km rail link, including planning, construction and maintenance throughout the operational phase.

SYSTRA, an international consulting group in engineering for urban and rail transportation, asked Astrium Services to provide an innovative solution to complement their existing information sources and methods to support their bid.

Discussions between Astrium Services and SYSTRA revealed a specific requirement. Along the initial 800 km route, only a 20 km wide footprint of satellite imagery and DEM data is actually useful.

The main requirement was to support the preliminary design study by providing precise and up-to-date geographic information across the entire area of interest.

Astrium Services' Solution

GEO Elevation and SPOTMaps

To support studies of the route of the new rail link, Astrium Services delivered a satellite dataset comprising of a Digital Elevation Model (DEM) and a high resolution mosaic of SPOT 5 orthoimages in natural colour.

This dataset covered the linear area of interest only, with an agreed minimal footprint width of 20 km along the 800 km route. The full dataset was delivered within 2 weeks.

Today, both products are available off-the-shelf for more than 40 million km² worldwide and can be delivered within 2 working days.

Results

The figure above shows the operational area: 27 viaducts (9km), 9 single-tube tunnels (11km), 5 twin-tube tunnels (2x38km), 83 million of earth moving works

Determination of earth excavation/fill volumes

Based on the SPOT DEM, the route of the rail link was converted into a longitudinal section, with viaducts and tunnels positioned in a 3D environment.
Earth excavation/fill volumes were determined on the basis of perpendicular cross-sections along the length of the longitudinal section.

These calculations were previously made using 1:10000 scale maps with a 20% margin of error. With Elevation30 DEMs, the margin of error is reduced to less than 10%.

Using Astrium Services' Digital Elevation Model plus SPOTMaps and without sending surveying teams on the ground Systra was able to deliver more accurate preliminary study results.

Faster and more accurate sizing

The DEM and Orthoimage set was fed into SYSTRA’s software system and also into a 3D presentation tool that lets users move around rapidly, identify locations and view existing developments/structures.
The combination of the two methods made it possible to optimize:

The route in accordance with land relief and gradients
The route in accordance with required train speeds
Incorporation of drainage networks
Visualization of property
Incorporation of other networks (roads, electricity grid, etc.)
Design of points/switching units
Location of stations

The preliminary design phase with determination of excavation/fill volumes and calculation of costs was completed without needing to send teams to the site or request authorizations from local authorities.

Benefits Satellite imagery as a source of geographic information combined with traditional tools and methods, allowed Systra to complete the preliminary design phase in a shorter timeframe and with reduced costs but also to submit a more competitive proposal.

Key benefits

The study was completed without the need to send surveying teams to the site or request authorizations from local authorities.
More accurate and quicker determination of earth excavation/fill volumes and structures identification.
The calculation for earth excavation/fill volumes were previously made using 1:10000 scale maps with a 20% margin of error. With the DEM, the margin of error was reduced to less than 10%. SYSTRA’s proposal was then based on more accurately adjusted figures and was ultimately more realistic.
75 million euros saved
Moving 1m³ of earth costs more than 5 euros. SYSTRA’s project involved 150 million m³ of earth at a cost of 750 million euros. A margin of error of less than 10% achieved by utilizing the DEM equates to a saving of more than 75 million euros.
Strenghtened communication with 3D visualisation
The 3D display system enabled Systra to show in advance what would ultimately be delivered

The preliminary design study was then conducted using a virtual reality system alongside conventional civil engineering tools.

About SYSTRA

The SYSTRA group, with offices throughout the world is a world leader in rail and urban transport engineering.

SYSTRA is working with local authorities and decision-makers to assist them in bringing their transport plans to reality. The group continuously develops its range of services and expertise to fully meet the needs of its clients for all aspects of sustainable mobility. This includes high-speed lines, conventional freight and passenger lines, urban rail, metros, automated guided systems, train-trams, tramways, Bus Rapid Transit and soft transport.

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