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El mundo al instante

Turbulence not the culprit for Northern Lights’ effect on GNSS

NorthernLights GNSS OResearchers at the University of Bath, U.K., have gained new insights into the mechanisms of the Northern Lights, providing an opportunity to develop better satellite technology that can negate outages caused by the natural phenomenon.

Previous research has shown that the natural lights of the Northern Lights — also known as Aurora Borealis — interfere with GNSS signals. Plasma turbulence within the Northern Lights has been deemed responsible for causing GNSS inaccuracies. However, the latest research found that turbulence doesn’t exist, suggesting new, unknown mechanisms are actually responsible for outages on GNSS signals.

This is the first time it has been shown that turbulence does not take place within the Northern Lights. The findings will enable new technological solutions to overcome these outages.

The research team from the University of Bath’s Department of Electronic & Electrical Engineering, in collaboration with the European Incoherent Scatter Scientific Association (EISCAT), observed the Northern Lights in Tromsø, Norway, where they observed and analyzed the Northern Lights simultaneously using radar and a co-located GNSS receiver.

GNSS signals were used to identify how the Northern Lights interfere with GPS signals. Radar analysis provided a visual snapshot of the make-up of the phenomenon.

The researchers believe this heightened understanding of the Northern Lights will inform the creation of new types of GNSS technology that are robust against the disturbances of the Northern Lights, and help influence GNSS regulations used in industries such as civil aviation, land management, drone technology, mobile communications, transport and autonomous vehicles.

“With increasing dependency upon GNSS with the planned introduction of 5G networks and autonomous vehicles which rely heavily on GNSS, the need for accurate and reliable satellite navigation systems everywhere in the world has never been more critical,” said university lead researcher and lecturer Biagio Forte.

“The potential impact of inaccurate GNSS signals could be severe. Whilst outages in mobile phones may not be life threatening, unreliability in satellite navigations systems in autonomous vehicles or drones delivering payloads could result in serious harm to both humans and the environment,” Forte said. “This new understanding of the mechanisms which affect GNSS outages will lead to new technology that will enable safe and reliable satellite navigation.”

The Northern Lights occur at North and South magnetic Poles, and are the result of collisions between gaseous particles in the Earth’s atmosphere with charged particles released from the sun’s atmosphere.

The research was published in the Journal of Geophysical Research: Space Physics.


http://www.gim-international
Viernes 17 de Marzo del 2017

SI Imaging Services Announces Reseller Agreement with Land Info

si

SI Imaging Services (SIIS) has reached a major reseller agreement with Land Info Worldwide Mapping (Land Info). The contract, effective from 1 January 2017, makes Land Info an authorised reseller of KOMPSAT data.

With this agreement, Land Info will expand its offering of value-added feature extraction and classification to include the use of KOMPSAT imagery.  Commenting on the new agreement, Nick Hubing, president of Land Info, stated that imagery from the constellation of KOMPSAT-2, KOMPSAT-3, KOMPSAT-3A and KOMPSAT-5 is an important addition to their on-line search tool, so customers have access to the broadest range of archive imagery. SIIS support for worldwide sales streamlines Land Info’s ability to support transnational projects.

SIIS contributes to remote sensing and Earth observation societies by providing very high resolution optical and SAR images through over 80 partners worldwide. The KOMPSAT (Korean Multi-Purpose Satellite) programme is a part of the Korean government’s space development programme, which provides very high resolution satellite imagery to the global remote sensing community. KOMPSAT 3A, the most recent optical satellite among SIIS’ products, offers 40cm resolution imagery for a variety of purposes such as mapping, infrastructure monitoring and natural resources.  KOMPSAT-5, the first Korean SAR satellite, offers very high resolution SAR imagery (up to 85cm) for change detection regardless of weather conditions.


http://www.gim-international
Viernes 17 de Marzo del 2017

Geomatics and Surveying in Support of Land Administration

Implementing Tenure Security for All

Today’s geospatial technology means that land administration systems can increasingly be implemented for the benefit of all. It is now possible to conceive approaches to capturing the unrecorded geometry of boundaries for the billions of unrecognised land interests or spatial units. In addition, new approaches are becoming apparent for the maintenance of collected data. Examples from the field show that we’re well on the way to responding to the challenge. From a geomatics and geoscience perspective, many tools are already available to support development, but further steps are needed to operationalise them at scale. Read on for an article investigating a few of the emerging options.

(By Christiaan Lemmen, Rohan Bennett and Paul Saers, The Netherlands)

Land information tells us about the ownership, use, value and development of land – whether statutory, informal or customary. It provides an overview of people-to-land relationships. It shows us how people relate to the space around them. The information can be used to realise responses to major societal challenges, e.g. the UN 2030 Agenda for Sustainable Development. Geoinformation and Earth observation provide the inputs. These include satellite and drone imaging and mapping, global navigation satellite system (GNSS) positioning, cartography, spatial data infrastructures and many surveying sub-disciplines. This article takes a look at how each of these tools is helping to operationalise land administration at scale – and also what challenges need to be overcome to realise the potential.  

Using Imagery

In the last few years, there has been considerable buzz surrounding ‘fit-for-purpose land administration’. The approach argues for cost-effective, time-efficient, transparent, scalable and participatory systems. The philosophy is driven by the idea that, in many situations, it is sufficient to identify visual boundaries based on imagery. This means making use of photographs, images or topographic maps in the boundary adjudication and mapping activities. Alternatively, apps on mobile devices can be combined with imagery to identify plots, thus avoiding misinterpretation of visual boundaries on the image. Images can be collected from satellites, traditional aircraft or unmanned aerial vehicles (UAVs). In cases of high land values or intensive land use, the field surveys can be conventional land surveys using high-precision total stations or GNSS.

Standardising Models

Alongside the push for the increased use of imagery, global standards such as the Land Administration Domain Model (LADM) focus on standardised modelling of information at the conceptual level. The model does not include processes for initial data acquisition, data maintenance and data publication. This is because those processes were considered to be country-specific when the first edition of LADM was prepared; a generic and global approach was likely to be difficult to model. This view now needs reconsideration, however. The fit-for-purpose land administration approach arguably allows for identification of more generic process-related modules in data acquisition and data handling. Standardisation can also make it easier to monitor the progress of global indicators relating to land tenure security.

Focusing on Processes

So what are some of these processes that might be supported? Examples include initial data acquisition, georeferencing (based on elevation models), identification of boundaries, surveying (based on imagery, conventional surveys, UAVs, digital pens for imagery and handwriting, feature extraction/data cleaning, radar), area management, linking rights, restrictions and responsibilities (RRRs) to spatial units, linking (groups of) persons to (shares in) RRRs, public inspection, publication of land data, formalisation, map renovation and quality improvement and digital archiving. Computerising large sets of legacy data (maps and archives) requires analogue-to-digital conversion, georeferencing and linking to digital data from other sources. Data may be used for taxation, tenure security purposes, slum upgrading, city management and so on. This also includes land use and zoning plans implemented by land consolidation and land readjustment processes. Statistical information such as fragmentation index and price index may need to be derived from the land administration. Imagery may be available on paper or on mobile devices in the field, or both.

Creating a Tenure Atlas

Another challenge in many countries is that several authorities may play a role in the process of recognising, recording, registering and managing the land tenure, and they may each maintain their own land information sets. Therefore, at national level, coordination is needed; a Land Tenure Atlas could be developed to provide an overview of the spatial distribution of legitimate tenure types throughout a country – be they customary, informal, private, public or otherwise. The Atlas may further include a layer for national and administrative boundaries and potentially a layer for planned and ongoing projects in land administration. The Atlas should be able to be aggregated to global level, enabling linkage to proposals for international data exchange representing the different RRRs in use within countries.

Utilising Devices

Surveyors and geoprofessionals focus on geometric accuracy, and this focus should result in quality labels identifying the relative and absolute accuracy of geometric data. This is relevant for later adjustment and integration of data from different sources collected with different instruments and tools in different approaches. But land administration is not only about geometric data. Talking about quality in land administration means not only talking about geometric accuracy, but also about ‘linking’ between polygons (spatial units) and people (right-holders). It would be nice if functionalities could be combined in one single device, i.e. linking functionalities for image-based data acquisition to handheld GPS, biometric data (fingerprint identification and facial recognition) and voice/video recording in support of object identification. Such devices would also be useful for inspections, for fieldwork related to building and construction permits, for cadastral maintenance, etc. Land data collected on many devices could deliver results in formats based on operational standards.

Integrating with OGC

The Open Geospatial Consortium (OGC) recognises that worldwide, effective and efficient land administration is an ongoing concern, inhibiting economic growth and property tenure. Existing approaches are at significant risk of data loss and failure due to disasters and lack of interoperability. The charter members of an established OGC Land Administration Domain Working Group are seeking to identify enabling standards and best practices to guide countries in a programmatic way towards establishing more cost-effective, efficient and interoperable land administration capabilities. Attention will be paid to upgrading currently manual processes to semi-automated ones, and to suggesting new approaches for data acquisition that are more automated and flexible. These challenges are faced today in ‘developing’ and ‘developed’ countries alike.

Developing Cooperation

Enabling standards are also being developed with other domain working groups within OGC, such as LandInfra. Partnerships and liaisons with other associations and standards developing organisations (SDOs) will be developed to address interoperability issues that span the land administration community of practice, geographic information systems and the broader IT environment. Examples include linkages with ISO TC 211 regarding the LADM as well as those SDOs responsible for IT standards related to topics such as security, the internet and mobile services. Further, the DWG will be open to participation by any interested organisations and individuals.

Industrialising Approaches

The geospatial industry provides tools, products and services in support of a number of important processes required in fit-for-purpose land administration. Image-based acquisition of cadastral boundaries needs access to huge image libraries – including historic imagery – to support large-scale implementations. Detection and selection of cloud-free imagery is needed to create cloud-free compositions, possibly from different sensors. By using orthophotos to produce spatial frameworks, the imagery is typically linked to the national geodetic reference frame through GNSS in space/on the aircraft and on the ground. Furthermore, automated feature extraction and feature classification appear to be very promising developments for the generation of coordinates of visual objects from imagery, and Lidar and radar technologies can also be used for this purpose. ‘Pre-defined’ boundaries resulting from feature extraction may be plotted on paper or visualised in interfaces, and can then be declared identical to cadastral boundaries in the field.

Modernising Demarcation

In general, fixing boundaries should be avoided in the preliminary stages. It has been shown that demarcation with monuments or beacons often takes 80 to 90% of the surveyor’s time. If demarcation is an absolute requirement, let people place the beacons themselves. Otherwise, it is a good idea to explore modern demarcation methods – smart markers could provide a good alternative. Modern markers like the traceable 3D radio frequency identification (RFID) markers can be detected and identified from a distance of several metres using a simple smartphone. The RFID in the marker can store administrative and positional data. It eliminates all known drawbacks of traditional markers. They could be used as main markers or georeferenced markers, supplemented by locally surveyed points demarcated with low-cost materials. RFID boundary marker strips cost less than EUR1 to produce – although that does not necessarily make it affordable in some countries, of course.   

Utilising UAVs

UAV or ‘drone’ technology is rapidly developing, although autogyro platforms may represent another possible solution for aerial image capturing. Such platforms can operate at low to medium heights, thus largely eliminating the risk of images being obscured by cloud. In some cases, walking can be an alternative to low-altitude flying, e.g. using a portable 3D laser scanning device, the surveyor can map a strip extending 200 metres to each side of the trajectory on foot.

Handling the logistics

Processes such as initial data acquisition may concern millions of spatial units (parcels) for which people-to-land relationships have to be determined. The organisation of this process requires geospatial support in logistics and case/task management based on geoinformation. This starts with gaining an overview of the density of information. This is about estimating the amount of spatial units in a project area for planning purposes. Provision of materials and tools to data collectors can involve paper-based or digital approaches. A paper-based approach entails using plotted images in the field. This means that the collected field-boundary evidence can be left with the local people, providing a scan is available for the land administration authority. However, even paper-based approaches require a comprehensive range of geospatial technologies. Logistics activities include the processes of creating awareness of and announcing participatory approaches, agreeing on citizens’ roles in the land administration process, and publishing status information online/offline, as well as performing checks on completeness before leaving a location. Collecting copies of people’s ID, photos, signatures, fingerprints and video/voice recording requires field devices and battery power/electricity.

Handling maintenance

Data maintenance can be ‘programme driven’ (systematic) or ‘sporadic’. ‘Programme driven’ means a complete and systematic new acquisition after some time. ‘Sporadic’ means case by case in a ‘transaction-driven’ way and relates to transactions in the land market (buying/selling, mortgaging, etc.). Quality upgrading can be part of the maintenance process. This may be required after digitisation of legacy data or in the case of urbanisation or urban planning. It is crucial that data collected using survey approaches based on different accuracies can be integrated together. This may require adjustment of new observations to existing coordinates in the field or within GIS. Quality upgrading may also entail integration of 3D cadastral data (this includes integration with standards such as IndoorGML, InfraGML, LandXML, CityGML, BIM/IFC) and marine cadastre.

Concluding remarks

Implementation of all the processes presented here is currently undertaken in different places based on customisation from available databases and GIS technology. This is a time-consuming activity which demands GIS and ICT development expertise. Standardisation is required for those processes and needed in order to bring scalable approaches – ones which can be easily implemented based on the defined purposes of each land administration project.

Further reading

  • Enemark, Stig, McLaren, Robin, Lemmen, Christiaan, 2015: Fit-For-Purpose Land Administration – Guiding Principles. UN-HABITAT/GLTN, Nairobi, Kenya
  • GIM International, 2016. Special Issue on Fit-For-Purpose Land Administration for Sustainable Development. Geomares Publishing, Lemmer, The Netherlands
  • OGC, 2016, Domain Working Group (DWG) Charter Land Administration. Open Geospatial Consortium. http://www.opengeospatial.org/projects/groups/landadmin


Biographies of the authors

Christiaan Lemmen

Christiaan Lemmen holds a PhD from Delft University, The Netherlands. He is a geodetic advisor at Kadaster International and visiting researcher at University of Twente/ITC, The Netherlands. He is director of the FIG Bureau OICRF. He is co-editor of ISO 19152 LADM.

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Rohan Bennett

Rohan Bennett gained his doctorate from the University of Melbourne, Australia. He is an associate professor working in land administration at the University of Twente/ITC, The Netherlands, where he is also director of the School for Land Administration Studies at ITC.

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Paul Saers

Paul Saers has an MSc in geodesy and geoinformatics. He is a geodetic advisor at Kadaster International in The Netherlands. He is specialised in the management of computerised land administration systems, BPR, ERP and QMS.

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http://www.gim-international
Viernes 17 de Marzo del 2017

Así será la Misión de Exploración 1 de la nave Orión

En una entrada pasada ofrecí una breve introducción al programa SLS-Orión. Hablé acerca de la nave Orión y de su módulo de servicio, y acerca del cohete que se está desarrollando para su lanzamiento, el SLS. Como también apunté en esa entrada, la primera misión de prueba de un sistema SLS-Orión, llamada EM-1 (Exploration Mision 1), está prevista para finales del 2018. Esta misión no será tripulada; pero, de ser exitosa, la siguiente misión, la EM-2, sí se planea que lo sea.

En este punto es necesario decir que, a petición de la nueva administración, en la actualidad se está llevando a cabo un estudio sobre la posibilidad de dotar de tripulación a la EM-1 con objeto de acelerar el programa espacial tripulado. Se espera que este estudio esté completo para principios de la primavera, por lo que en esta entrada voy a hablar acerca de cómo se plantea la misión EM-1 en la actualidad.

En realidad, el sistema Orión está formado por el módulo de mando, o CM (Command Module o Crew Module), el módulo de servicio, o SM (Service Module), y la torre de escape, o LAS (Launch Abort System), la cual entraría en servicio para separar al módulo de mando del cohete en caso de explosión del lanzador. Dado que el LAS se separa del conjunto una vez se ha producido con éxito el lanzamiento, utilizaré el término Orión para referirme al conjunto formado por la unión entre el CM y el SM, los cuales permanecen unidos hasta pocos momentos antes de que el CM efectúe la reentrada en la atmósfera a su regreso a la Tierra.

Sistema Orión. Fuente: NASA.

La EM-1 tiene por objetivo volar a la Luna e insertarse en una órbita alrededor de nuestro satélite cuyo punto más alejado de su superficie será de unos 70.000 km. A esta órbita la llamamos Órbita Retrógrada Distante, o DRO, del inglés Distant Retrograde Orbit. Es retrógrada porque en ella la nave volará en sentido contrario al de rotación de la Luna, y es distante porque, como se ha dicho, el apolunio de dicha órbita se situará a unos 70.000 km de distancia. Para conseguir insertarse en esta órbita y después regresar a la Tierra, a lo largo de EM-1 se habrán de dar numerosas maniobras propulsivas.

En primer lugar, Orión será lanzado al espacio por el cohete SLS desde el complejo de lanzamiento 39B en el Centro Espacial Kennedy de la NASA en Florida. Después del lanzamiento, Orión estará aún acoplado en órbita alrededor de la Tierra a una etapa propulsora llamada ICPS (Interim Cryogenic Propulsion Stage) cuya función es la de impulsar al conjunto a la Luna gracias a un encendido de su motor en una maniobra que se conoce como Inyección Trans-Lunar, o TLI, del inglés Trans-Lunar Injection

ICPS unido a Orión en órbita alrededor de la Tierra antes del TLI. Fuente: NASA.

Gracias al TLI se consigue el incremento de velocidad necesario para que Orión se aleje de la Tierra siguiendo una trayectoria que lo llevará a encontrarse con la Luna unos días más tarde. De camino al satélite, el ICPS se separa de Orión, dejando que los módulos de mando y servicio unidos hagan el resto del viaje en solitario.

Durante la travesía, los datos de la trayectoria son analizados constantemente en tierra gracias al seguimiento que se hará de la nave a través de la Red de Espacio Profundo, uno de cuyos tres complejos se encuentra en Robledo de Chavela, en la provincia de Madrid. De haber algún tipo de desviación en la trayectoria que resultara en no llegar al entorno lunar en las condiciones idóneas, el módulo de servicio será el encargado de corregir el curso a través de pequeños encendidos ejecutados por su sistema de propulsión. Cada una de estas maniobras de corrección recibe el nombre de OTC, o Outbound Trajectory Correction.  

Esquema de la misión EM-1. Fuente: Airbus.

Al aproximarse a la Luna, la atracción gravitatoria de este cuerpo hará que la trayectoria seguida por Orión se curve alrededor del satélite hasta sobrevolarlo a unos 100 km de altitud. Es aproximadamente en ese punto donde el SM ejecutará un encendido llamado OPF, o Outbound Powered Flyby. El propósito de la maniobra OPF es colocar a Orión en una trayectoria alrededor de la Luna que un tiempo después lo lleve a un punto en el que se darán las condiciones ideales para insertar a Orión en la órbita de destino, la referida DRO. Esta inserción se ejecuta mediante otra maniobra propulsiva que tiene lugar más adelante y que recibe el nombre de DRI, o Distant Retrograde orbit Insertion.

Una vez insertado en la DRO, el conjunto CM/SM estará volando a lo largo de esa órbita durante unos seis días. A pesar de que la DRO es una órbita bastante estable, no se descarta que se pueda necesitar alguna pequeña maniobra de corrección para su mantenimiento. Estas maniobras son referidas como OM, de Orbit Maintenance.

Después de estos seis días, la nave efectuará la primera maniobra con la que se iniciará el regreso a la Tierra: la DRD, o Distant Retrograde orbit Departure. Mediante la DRD, la nave saldrá de la órbita DRO, haciendo que la trayectoria seguida vuelva a aproximarse a las cercanías de la Luna, de nuevo hasta una distancia de unos 100 km sobre su superficie. Será alrededor de este punto en el que la nave ejecutará la maniobra RPF, o Return Powered Flyby, por la que se la impulsará definitivamente de vuelta a la Tierra.

Al igual que en el tramo de viaje hacia la Luna, a lo largo de la travesía a la Tierra también es posible que sea necesaria alguna corrección de la trayectoria para procurar que la nave entre en la atmósfera en el punto deseado y con el ángulo adecuado. En este caso, a cada una de estas maniobras de corrección se las llama RTC, o Return Trajectory Correction.

Una vez llegado el conjunto CM/SM a las inmediaciones de la Tierra, el SM se separará del CM para que éste efectúe la reentrada en la atmósfera. Esta reentrada se hará a una velocidad de unos 11 km/s, que es la que la nave tiene en su retorno de la Luna, y llevará a la nave a amerizar cerca de la costa de San Diego, en el Océano Pacífico.

Como vemos, la EM-1 es una misión ambiciosa en la que se probarán muchos elementos y sistemas por primera vez y en la que se realizarán numerosas maniobras de diferentes características. A lo largo de los próximos meses, hasta su lanzamiento, seguiremos visitando su evolución junto con la de varios de sus sistemas, así como hablaremos sobre temas relacionados con los hitos que se vayan consiguiendo en su puesta a punto. 


http://www.elmundo.es
Jueves 16 de Marzo del 2017

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