3D Handheld Scanning of Historic Buildings

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Cataloguing the Intricacies of Oxford University

 

 

 

Oriel College in the UK is blessed with alumni including two Nobel laureates, one of them being a founding member of the Oxford Movement (the Catholic revival in the Church of England). While the academic prowess of the college is not in any doubt, the structural integrity of an institution that was founded in 1326 is naturally less certain. Located in the heart of Oxford and made up of a myriad of buildings, with around 200 rooms across five storeys fulfilling a variety of uses, Oriel College presented unique scanning challenges.

The custodians of Oriel College needed to assess the physical ‘health’ of their ‘Island Site’, a hidden-away part of the college only usually accessible through two entrances, one of which is a tunnel with step access. The likelihood of encountering unforeseen issues with the buildings (particularly when a structure has been added to and developed over the years) was high. As such, accurate floor plans and elevation drawings needed to be created based on mobile mapping data, displaying exactly how the building was built. This included all quirks and irregularities that are of interest for future structural improvements or changes to the buildings. A challenging handheld mobile mapping project was performed to create these maps and CAD drawings of this part of the University of Oxford.

Time pressure

The mobile mapping project was challenging not only due to the age and intricacy of the structures, but also due to the fact that the mapping needed to take place in as little time as possible to avoid disruption to daily operations. Meanwhile, it was important to obtain sufficient data without compromising on the accuracy of the results.

With some historical sites, it is possible to choose a time to scan when the buildings are closed to the public or not in use. Oriel College, however, is a world-class teaching, learning and research institution that has visitors, staff, students and alumni present at all times of day, all year round. In fact, many of the rooms would be in use during the scan as it was exam time, or serving as student accommodation with the associated privacy constraints. With over 40 fellows, 300 undergraduates and 160 graduates occupying the college, the mapping needed to be as swift as possible to minimise disruption.

Unconventional layout

Due to the unusual shape of the building, with its unconventional layout and complex network of rooms, it would prove difficult and time-consuming to survey with traditional static scanning methods (as this would require multiple individual set-ups and increased post-processing work). Added to the fact that static surveying methods can be more intrusive and require the team to stay significantly longer on site, it was also recognised that physically collecting data by measuring the space with traditional tools such as laser distance measurers or tape measures would not be suitable for Oriel College.

SLAM technology

The chosen tool was the GeoSLAM ZEB-REVO, a handheld, lightweight, mobile indoor mapping tool that can record over 43,000 measurement points per second. The ZEB-REVO employs a very robust 3D simultaneous localisation and mapping (SLAM) algorithm, which is at its best in complex, enclosed, multi-level environments. This SLAM technology utilises data from a Lidar sensor and an IMU to identify unique three-dimensional (3D) structures within the survey environment, and creates a point cloud of these structures. This iterative process occurs constantly as the user walks through the environment and builds up a 3D model of the space. Since the ZEB-REVO unit contains an IMU, it does not require a GPS signal for positioning. As well as recording heritage buildings, the ZEB-REVO is used in other projects for generating footprints, estate agency requirements and scanning to building information modelling (BIM). Without the need for comprehensive training to use the device, the team was able to ‘pick up and go’ with the ZEB-REVO tool, saving additional preparation time for any members of staff previously unfamiliar with the technology. The team’s previous experience indicated that GeoSLAM ZEB-REVO would significantly cut time and costs, while still reaching an average accuracy level of 15mm, making it a very suitable technology for this project.

Results

Thanks to the scanner’s speed, the space could be surveyed in a very short amount of time, which was particularly important due to the limited time available in certain rooms. Using the ZEB-REVO around 200 rooms were scanned, amounting to 12,000m2 in total. Across five days, 12 individual rapid ZEB-REVO scans were completed, each taking around half an hour. Taking into account ten days to produce the CAD drawings, the entire project was completed in around half of the total time that would have been required using static equipment, reducing an estimated 44 days down to 24. The final drawings were revelatory, showing just how irregularly the college buildings were arranged. As an institution with such a long history, it was also fascinating to discover how the college has been adapted and added to over time by different caretakers and building managers. Representing the buildings in their truest form (3D) made it possible to highlight the faults, features and façades that required attention or future planning to preserve.

Next steps

Using non-intrusive and accurate technology like the ZEB-REVO provides detailed accounts of a facility’s structural limitations. The next step in this project is the generation of complex BIM-ready 3D models from this 3D scan data. Such models can be used as a ‘digital twin’ of the building, allowing for building modifications and adaptations to be worked into the 3D model – either before or after the actual works have taken place. The use of geomatics technology has enabled the preservation of this historical institution from a heritage perspective, as well as ensuring that Oriel College can continue to provide education of the highest possible order for many years to come.

Further reading

For more information on GeoSLAM’s ZEB-REVO, visit www.geoslam.com.

The author

Peter Maxwell is an expert in the provision of topographical surveys, measured building surveys and underground utility land surveys and works as an IT manager at Midland Survey Ltd in the UK.

China, a un paso del teletransporte cuántico en el espacio

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De momento habrá que esperar hasta que el teletransporte de personas, al estilo Star Trek, descongestione las autovías. Esta opción es hoy en día pura fantasía, pero, desde el año 1993, el teletransporte de información es una realidad en el laboratorio y hay empresas que buscan utilizarlo para crear redes de comunicación. Su gran ventaja es que los mensajes intercambiados resultan indescifrables, gracias a que se usa un recurso conocido como criptografía cuántica. Una forma limitada de esta criptografía cuántica se usa hoy en día en comunicaciones terrestres, vía láser o fibra óptica, a una distancia de hasta 100 kilómetros.

El pasado 16 de agosto de 2016 China lanzó el primer satélite cuántico al espacio, en la misión QUESS («Quantum Experiments at Space Scale»), para comprobar si esta tecnología podría usarse para hacer una red de comunicaciones cuánticas en el espacio. Este jueves, un artículo publicado en Science por los científicos chinos ha puesto la primera piedra de esta tarea. Los investigadores han logrado conseguir el entrelazamiento de fotones, una propiedad de la Mecánica Cuántica a la que Einstein bautizó irónicamente como «fantasmagórica reacción a distancia», entre dos estaciones terrestres separadas por una distancia de 1.200 kilómetros, vía satélite. Después de este hito, lograr el teletransporte de información entre dichas estaciones es tan solo un paso sencillo.

«Es un avance muy importante. Han logrado extender el rango de la potencial criptografía cuántica de los cien kilómetros hasta los 1.200 kilómetros», ha explicado a ABC Juan José García Ripoll, investigador del Instituto de Física Fundamental (IFF-CSIC).

China, que fue considerada por Nature como el país «pionero de la tecnología cuántica en el espacio», cuenta con varias redes cuánticas indescifrables para unir ciudades e instituciones. El problema es que dichas redes como mucho pueden tener una longitud de 100 kilómetros, por lo que están conectadas entre sí por canales convencionales, de modo que su seguridad podría quedar vulnerada en las rutas de enlace. La forma de evitarlo es usar una conexión cuántica vía satélite. De ahí la importancia de este último avance.

Prioridad para la NASA y Europa

El entrelazamiento y el teletransporte son unos fenómenos que ocurren a la escala de lo más pequeño y que permiten que fotones separados se comporten como los reflejos de un espejo, aunque estén separados por distancias enormes. Como los fotones se pueden enviar para mandar información, como ocurre con la fibra óptica convencional, este fenómeno también se puede usar para intercambiar datos. Y además hacerlo de un modo a prueba de «hackers» y oídos indiscretos.

De hecho, la NASA y otros organismos ya llevan varios años trabajando en sistemas de comunicación similares, en los que los fotones (partículas cuánticas) que han sido previamente entrelazados, funcionan como unidades transmisoras de información (bits) a largas distancias, aunque no haya ningún sistema que físicamente los una. En parte para potenciar esta tecnología, en 2018 la Unión Europea lanzará un proyecto «flagship» financiado con 1.000 millones para financiar estas investigaciones.

El teletransporte

¿Cómo funciona el teletransporte de información? La receta para lograrlo consiste en entrelazar fotones. El entrelazamiento es una característica de la Mecánica Cuántica por la cual dos partículas «coordinan» o correlacionan sus estados cuánticos de forma que el valor de cualquier propiedad, como la polarización de un fotón, es el mismo para ambas partículas (por eso se puede decir que una es el reflejo de otra). Por muy lejos que estén dos fotones entrelazados, al medir el estado cuántico de uno en un sitio, automáticamente se obtiene el mismo resultado en un sitio distinto.

Pero hay algo más. En realidad el estado de ambos fotones nunca está definido, porque se encuentra en una superposición aleatoria de muchas posibilidades.

Por eso, si alguien intercepta uno de los fotones solo obtendrá un resultado aleatorio. A menos que tenga una «clave» para leer el estado de dichos fotones de forma correcta. Esta clave se puede enviar de forma convencional, y por sí sola no tiene la información suficiente como para que alguien externo que la intercepte entienda el mensaje.

Una limitación de esta tecnología es la distancia. A medida que los fotones viajan por una fibra óptica, se van perdiendo y en ocasiones también van «olvidando» su estado cuántico (esto se conoce como decoherencia). Cuanta mayor sea la longitud recorrida, más probable será que esto ocurra y que, por lo tanto, ser pierda el mensaje por el camino.

Pero al usar un satélite conectado con Tierra, se sustituye esta fibra óptica por una franja de varios kilómetros de atmósfera, en la que es más difícil que los fotones pierdan información al chocar con las partículas del gas.

Un futuro de comunicaciones invulnerables

En esta ocasión, los investigadores chinos lograron generar pares de fotones entrelazados a bordo del satélite Micius, y enviar cada uno de ellos a sendas estaciones receptoras en Tierra, separadas por una distancia de 1.200 kilómetros. Gracias al entrelazamiento, los resultados de la medida del estado cuántico de los fotones fue el mismo en las dos estaciones.

En realidad, esto no siempre funcionó, y se cometieron muchos errores. Por eso, para que esta tecnología realmente puede ser útil en el futuro, aún será necesario mejorar la precisión del envío, mejorando los sistemas receptores y la emisión de los fotones.

Una vez conseguido un entrelazamiento más fiable entre fotones enviados del espacio a la Tierra, y viceversa, una red terrestre (por ejemplo la de un banco o una institución estratégica del estado) podrá utilizar los fotones entrelazados generados por el satélite, para distribuir información cuántica usando teletransporte cuántico a grandes distancias. Cuando eso ocurra, las comunicaciones podrán ser totalmente seguras, a prueba de «hackers» y supercomputadores capaces de descifrar claves.

Handheld Land Administration Mapping Methods in Kenya

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Institution of Surveyors of Kenya Demonstrates Alternative Approaches 

 

 

 

 

Fit-for-purpose approaches to land administration have been tested in Kenya, with a focus on the provision of land titles with inclusiveness for all in an approach that is affordable, fast and ‘good enough’. Earlier this year a group of Kenyan surveyors performed a field test in Makueni County, collecting land data using handheld devices. This first test was a learning experience; a more comprehensive test must be conducted to prove the scalability of the approach.

(By Stephen Ambani and Judith Kalinga, Kenya, and Christiaan Lemmen, The Netherlands)

The fit-for-purpose approach recommends the use of ‘visual boundaries’ to identify the delineation of land rights. There are many naturally visible boundaries in rural areas in Kenya, and the local people have made some other boundaries visible using sisal plants. During the field test performed by a group of Kenyan surveyors to trial a fit-for-purpose approach, all boundaries were easy to identify in the field and on satellite imagery. After being identified in the field, the visual boundaries were then drawn in an analogue manner using a pen or ‘digitally drawn’ using handheld GPS devices on top of imagery.

All land rights

Making an overview of all existing people-land relationships includes formal ownership and informal land use, as well as possession and occupancy of lands. The overview of the existing situation should also reflect overlapping claims, disputes and conflicts, since it is crucial for the authorities to get an overview of spatial units or boundaries under dispute. This ‘dispute map’ is the starting point in supporting the dispute resolution procedures. Dispute mapping is already done in other countries, just as imagery is used for cadastral mapping. The test in Kenya was an initiative by the surveying community to find out how to organise support and nationwide introduction of a fit-for-purpose approach.

Participation

Community involvement is the basis for success. Cadastral survey requires the participation of neighbours, family members, etc. Therefore, the village elders and other villagers are informed in advance to ensure awareness and involvement of all parties (see Figure 1). Everyone can monitor the on-site process in the field. During the field test, the collected data was transmitted from the mobile device directly to a cloud-based GIS environment, enabling everyone to follow the process remotely and creating ‘remote participation’. 

How does it work?

Fieldwork is about creating an overview of all existing people-land relationships, including formal ownership and informal land use and also overlapping claims. Villagers and farmers are invited to walk the perimeters of their land parcels and point to the vertex points of the boundaries themselves using a GPS antenna. An experienced surveyor or grass-roots surveyor records the observations with the Collector app from Esri. Satellite imagery of the area is displayed on the screen of the mobile device (see Figures 2a-2c). Data collection is done in an integrated way: the perimeter is stored as a closed polygon together with the claimed type of right combined with a photo of the owner or claimant and a photo of the owner’s or claimant’s ID (Figure 3). A preliminary identifier is used as linking key. Accuracy is not so much about the geometry, but is rather focused on linking spatial and administrative data or, in other words, linking people to polygons. Since citizens are required to provide proof of their identity, the government has to be represented in the field. This is of general importance for the success of this methodology.

Disputes

It is crucial to get an overview of parcels or boundaries under dispute and at the same time an overview of all the areas which are not under dispute. ‘Dispute holders’ need to ‘agree’ on the area and location of the dispute. During the adjudication process in the field, disputes may lead to the creation of overlaps between polygons. In that case, those overlaps are mapped and the corresponding authorities know the exact location of which type of land-related conflict.

Data handling

After field data collection, the data must be checked for completeness and prepared for public inspection. Some editing was needed in order to present the spatial data – this concerned mainly the calculation of average locations of boundaries based on the input from the neighbour on each side of the boundary.

Public inspection

Usual procedures, such as public inspections, are conducted at village meetings – often in the local town hall – accompanied by trusted third parties. At a village meeting (which in the field test was held in the local church), community members gather to view all the collected data on a map and discuss and reconcile the results. In the field test, the presented data was loudly confirmed by the community.

Configuration

The design environment in this case is based on Esri’s Collector app, which enables very efficient data collection. The app is used in combination with a GPS device for sub-metre accuracy, via a Bluetooth connection. Devices from Trimble and other suppliers can be used. Lightweight devices in the field are very efficient to use in mountainous Kenya, and the tools and technologies to develop the application are available. The GPS device requires a correction signal for correction of atmospheric distortions of the GPS signals. Sub-metre accuracy is sufficient. High accuracy is not needed – no beacons need to be placed. It is important to gain an overview of the plots with a highly reliable link to the type of right and the owner. If necessary, placing beacons and highly accurate surveys can be done later during the maintenance phase. This can also be done by the people themselves.

Field test

The field test conducted in Makueni County in 2017 demonstrated that the field data collection and data handling can be carried out quickly, affordably and reliably. This test was carried out by the Institution of Surveyors of Kenya, the National Ministry of Lands, Housing and Urban Development and the Ministry of Lands, Mining and Physical Planning in Makueni County, in close collaboration with software and hardware providers.

Institutional commitment

There is attention to this approach at the highest level. Prof Jacob Kaimenyi, the Minister of Lands, Housing and Urban Development of the Republic of Kenya, welcomed a delegation from the Institution of Surveyors of Kenya (ISK) and Kadaster International to his office at Ardhi House in Nairobi. The delegation informed the minister about the goals and potential impact of the test and introduced the fit-for-purpose approach to land administration. The chair of ISK explained the benefits of the approach, and this topic now has the minister’s attention.

Prof Kivutha Kibwana, a representative of the Governor of Makueni County, and the Minister of Lands, Mining and Physical Planning of Makueni County welcomed the delegation to the Governorate of the County. The test was done in this county and had permanent attention of the minister herself. The word of welcome was followed by intensive discussions on the approach: on participation, on quality and costs, on time effectiveness, on the need for monumentation, on accuracy versus coverage, etc. The minister underlined the importance of alternative approaches. However, this innovative approach may have some impact on existing regulations, and there is also the issue of how to store and manage the integrated data. Should the data be divided into a cadastral subset and a registry subset, with different object IDs? These are important issues to discuss as the basis for future development. A further issue is whether the data can be kept fully digitally after the fieldwork, or whether paper-based storage is needed. Or perhaps a paper copy of the satellite image should be left to the local community as the ‘people’s data’. Notably, in Kenya it is already commonplace for the boundaries to be drawn by hand on top of imagery, including in the test area (see Figure 4).

Concluding remarks

The field test conducted in Makueni County in 2017 demonstrated that the field data collection and data handling can be carried out in an integrated, participative, fast, affordable and reliable manner. Figure 5 shows the results. Two surveyors collected data about 40 parcels in the space of six hours in a mountainous environment and the results were well received. However, the legal and institutional set-up requires attention in order to be able to implement the approach, and most of the participants agreed that the approach needs further attention in order to bring land titles for all.

It is estimated that, at this point in time, approximately 20% of the land parcels in Kenya have been surveyed (in one way or another) and are registered. The current cost to adjudicate, demarcate, survey, map and register a two-hectare parcel in Kenya is at least a few hundred dollars per parcel. In terms of the total cost, there are an estimated 15 million of parcels still to be included in the registry. It is clear that this amount of money is simply not available.

Alternatives are needed – or should at least be a topic of debate amongst professionals. An alternative methodology is presented here to ignite this debate. It is proposed to organise this debate now, with an open mind and a focus on the future. A more comprehensive test will lend support into this debate, and ISK is optimistic about the potential.

Further reading

Enemark, S., McLaren, R., Lemmen, C., 2015. Fit-For-Purpose Land Administration – Guiding Principles. UN-HABITAT / GLTN, Nairobi, Kenya. Available at:

FIG and World Bank, 2014. Fit-For-Purpose Land Administration. FIG Publications No 60, FIG Office, Copenhagen.

Molendijk, M., Morales, J.M. and Lemmen, C.H.J. (2015) Light mobile collection tools for land administration : proof of concept from Colombia. In: GIM International, Volume 29, November 2015.

About the Authors

Stephen Ambani, c­hair of the Instituti­on of Surveyors of Ke­nya, is a licensed lan­d surveyor with 21 ye­ars’ experience. He i­s very passionate about ­resolving challenges that ­hinder citizens in acquiring land owne­rship documents.

Judith Kalinga is the Minister for Lands, Mining and Physical Planning of Makueni County in Kenya. A qualified lawyer, she seeks to use the law to solve land problems rather than compound them. Judith sees a fit-for-purpose approach as a structured way of achieving this objective.

Christiaan Lemmen is geodetic advisor at Kadaster International. He is visiting researcher at the Faculty of ITC, University of Twente, The Netherlands and chair of the Fit-For-Purpose Land Administration Working Group of FIG Commission 7 on Cadastre and Land Management.

 

¡Sorpresa! Júpiter es más antiguo que el Sol

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Un equipo de investigadores de la Universidad de Münster, en Alemania, ha descubierto que Júpiter es el más antiguo de los planetas del Sistema Solar. Pero no solo eso, sino que el análisis de ciertos isótopos presentes en meteoritos sugiere que el gigante gaseoso podría haberse formado incluso antes de que el propio Sol empezara a brillar. El extraordinario hallazgo acaba de publicarse en la revista Proceedings Of The National Academy Of Sciences.

Para conseguir un modelo fiable de la edad de Júpiter, los investigadores, liderados por el astrónomo Thomas S. Krujier, midieron las concentraciones de isótopos de molibdeno y tungsteno en meteoritos ferrosos.

Existen dos clases de meteoritos de hierro, y Krujier y su equipo sostienen que ambos tipos se formaron por separado en el interior de la nube de polvo y gas de la que surgió nuestro Sistema planetario.

Estas dos familias de meteoritos representan, según se explica en el artículo, «dos reservas genéticamente diferentes dentro de la nebulosa original, que existieron al mismo tiempo pero que no llegaron a mezclarse» durante los primeros millones de años de formación del Sistema Solar. Para los investigadores, la explicación más plausible para esta separación física es la formación de Júpiter entre ambas.

Júpiter pertenece a un tipo de planetas llamados gigantes gaseosos.Probablemente, su nacimiento implica, primero, la formación de un núcleo sólido, seguido por un largo periodo de acumulación de gruesas capas de gas a su alrededor.

Krujier y su equipo calcularon que el proceso empezó en una etapa muy temprana de la formación del Sistema Solar, que nació cuando parte de una gigantesca nube molecular se condensó bajo su propia fuerza gravitatoria, hace unos 4.600 millones de años.

20 veces la Tierra

Según el modelo de los investigadores, el núcleo interno de Júpiter creció hasta alcanzar 20 veces la masa de la Tierra en el transcurso del primer millón de años. En ese momento, el Sol era aún una protoestrella, y no tenía la densidad suficiente como para que en su interior comenzara el proceso de fusión del hidrógeno.

El crecimiento de Júpiter continuó aunque a un ritmo más lento, hasta alcanzar las 50 masas terrestres unos tres millones de años después.

«Por lo tanto -reza el artículo de Proceedings- Júpiter es el planeta más viejo del Sistema Solar y su núcleo sólido se formó incluso antes de que la nebulosa solar se disipara». Para los investigadores, haber sido capaces de fijar una fecha para la formación del planeta más grande de nuestro sistema permitirá llevar a cabo análisis más detallados de cómo su presencia afectó al nacimiento y desarrollo del resto de los planetas, incluido el que nosotros