Remote sensing: the science of interpreting and identifying features from a distance.

By iLaria Marengo

Remote sensing is the fascinating science that studies and exploits the way the light coming from the sun (or from another source, e.g. radar) is first absorbed and then reflected back to the atmosphere by the objects on the Earth’s surface. Contrary to GIS, whose basic concepts are relatively simple and more “user friendly”, remote sensing is a sort of “niche” discipline because it involves more physics and maths, and requires skills in image interpretation. Nevertheless, remote sensing, coupled with GIS, is a powerful tool for understanding the spatial and temporal changes of the environment and deriving useful information to support environmental policies, decisions on management planning and strategies.

From the 5th to the 13th of November, the Ascension Island Government Conservation Centre (AIG CC) hosted a training course in remote sensing as part of the capacity building supported by the Darwin Initiative project entitled “Mapping Ascension Island’s Terrestrial Ecosystem”. The course was run by Dr Johanna Breyer, who works at Environment Systems in Aberystwyth, and has been contracted to support AIG CC in the delivery of the Darwin Initiative project. Environment Systems is a well-established consultancy company with years of experience in the field of remote sensing and GIS analyses. Johanna’s main task is the processing and interpretation of the high resolution World View 2 image (2 metre resolution) by applying a rule-based object analysis called image segmentation.

Data managers from the Falkland Islands and Saint Helena governments were invited to attend the course with the intention of becoming “intelligent consumers and users” of remote sensing tools. The aim of the course was to better understand the concepts behind remote sensing and apply them specifically to habitat classification. Central part of the course was to learn how the remote sensing analyst operates when carrying out the image segmentation and how the field surveyors proceed in determining and validating the classes of habitats on the ground and with the help of statistics. Time was spent in the office and on field trips to various locations in Ascension, with a very interesting off road traverse of Green Mountain from east to west.

satellite-map False colour image of Ascension (IR, red, green) to highlight the vegetated (red) and not vegetated (greyish) land. Clouds are visible in white.

signatureSpectral signature plot of water, bareground and vegetation. According to the signature the remote sensing analytical tools are able to identify and distinguish the objects on the surface.

There were many lessons learned from the hard job that Sam and Phil did in terms of habitat classification, for instance using systematic approach in deciding the sampling points and in assessing the habitat (use a standard density scale, consider the height of the species, carry out the assessment according to three altitude zones, etc). Similarly, Johanna provided the necessary basis to become aware of what a remote sensing analyst needs in order to set the rules for the image segmentation and extract the objects that will match the habitat classes. Interpreting a satellite image means being able to read and understand the spectral signatures that describe how the light is absorbed and reflected by the objects. In addition, ancillary information can help in identifying the objects, along with the knowledge of the local ecologist. At the end is a matter of aligning what a remote sensing analyst can extract from the satellite image and what the ecologist can see and map from the ground.

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Field works on a lava flow which hosts the sooty terns

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The spread of the invasive Mexican thorn bush on the slope of the Devil’s Riding School

Although the rule-based image segmentation is carried out using commercial software, QGIS, the open source software being used across the South Atlantic overseas territories, provides a series on interesting plugins, such as Semi Automatic Classification and Orfeo tool box, which can be used as starting tools for unsupervised/supervised classifications and for practising what was learnt at the course. Furthermore, free Landsat images offer the opportunity to perform spatial/temporal analyses in QGIS and detect land cover changes which affect the territories.

An important outcome of the course was talking and drafting best and standard practice for habitat classification with the use of remote sensing and ecological knowledge that can be applied across the South Atlantic UKOTs. In fact, the goal is to transfer what has been achieved in Ascension to projects that will be run in Saint Helena and the Falklands in the future.

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Turks and Caicos 2ND UKOTs GIS-Workshop: Learning, Sharing, Coming Together and Building Collaborations Across Territories.

By iLaria Marengo

Turks and Caicos Islands (TCI) hosted, from the 2nd to the 6th of February, the second UKOTs GIS workshop which saw the participation of representatives from the Caribbean (Anguilla, BVI, Bermuda and Cayman), Europe (Gibraltar), the South Atlantic (the project manager of the IMS-GIS data centre for Falkland Islands, Ascension, Saint Helena, Tristan da Cunha and South Georgia), Joint Nature Conservation Committee (JNCC), Environment Systems, and National Oceanography Centre (NOC). The event was fully supported and organised by the JNCC and by TCI Department of Environment and Maritime Affairs (DEMA).

The workshop entitled “understanding our islands: how to get the best out of our GIS and data” was focussed on achieving the following goals:

  • Providing members of TCI governmental departments with a training course in QGIS to allow them to become familiar with the open source program and demonstrate that it is a valid option to the proprietary and more expensive ArcGIS;
  • Identifying data priorities for TCI and finding solutions on how to address them in terms of GIS applications and data management;
  • Developing GIS and data management strategies to obtain long term benefits, such as standardisation of data, networking and data sharing, but also immediate gains, e.g. GIS and Remote Sensing based spatial analyses to support decisions on the islands’ policy priorities;
  • Looking at the main components of data management, which are people, data and systems and examine the way of tackling each one. The presentations on effective case studies delivered by each of the OTs offered “food for thought” and a starting point for discussion;
  • Drawing action plans to implement a sound data strategy in each territory and take forward the best practice of using GIS and Remote Sensing techniques as decision support tools.

The first two days of the workshop were entirely dedicated to the training in QGIS and had the participation of four TCI governmental departments: DEMA, Disaster Management, Planning and Surveying/Mapping. The training, led by Dr Katie Medcalf (Environment Systems) with the help of Dr iLaria Marengo (IMS-GIS data centre project manager), explored how to import the data, how to run basic vector analysis, how to create a map, and highlighted the best practice for structuring tabular data. In addition, practical examples of how Remote Sensing can be advantageous for evaluating environmental and ecosystem services were provided, as well as how spatial databases store and analyse geographic data more efficiently. Participants learned how GBIF can play a role for data sharing and how to upload/download data from it.

Besides the practical exercises, time was also spent discussing the current data management in TCI. Problems were identified and possible alternatives and solutions were found and translated into an action plan which should work as a starting point for the next months. The positive aspect of the first two days was the enthusiasm and the determination showed by TCI participants. Their genuine interest and desire to learn how QGIS works and how it can be advantageous to their project was a motivation for those delivering the training. TCI is currently facing two main problems: communication and data sharing among departments and consequently the lack of organisation and a data management system. The most evident and appreciated result at the end of the first two days was to see everybody discussing and finding solutions together round the table.

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The excitement and interest in GIS and data strategy increased even further when the other UKOTs joined the workshop on the 4th of February. The discussion on how to make the most out of spatial data became wider and the presentations of projects and activities carried out in the Caribbean, Gibraltar and the South Atlantic were extremely inspiring.

Stephen Warr from Gibraltar wowed the audience once again with his demonstration of the advanced use of GIS and 3D modelling for environmental and planning purposes. Many people desired to have the drone and the plane with fitted camera that Jeremy Olynik from the Cayman showed in his presentation. Both are very useful technologies for getting high resolution data of areas that are not easily accessible. It was particularly interesting to learn about outreach activities from Rozina Norris-Gumbs which involve taking GIS to the schools and hosting a GIS day every year in BVI. Andre’ from Anguilla presented a superb use of remote sensing and GIS techniques to assess ecosystem services for his island. His motto “seeing is believing” was clear: to the politicians’ eyes maps realised from validated and sound data are more effective and compelling than reports. Mandy Shailer explained to us the way in Bermuda spatial data from aerial photography offer evidence and support for conservation and planning studies. iLaria Marengo, who represented the whole SA UKOTs, described the advantages of having a metadata catalogue online and how the data strategy for the entire region tackles issues such as data accessibility and data licence agreement.

Presentations from Tara Pelembe and Steve Wilkinson (JNCC), Katie Medcalf (Environment Systems) and Alan Evans (NOC) were very important as they described how their organisations can assist the territories in bidding for grants, addressing data management issues, providing technical consultancy on spatial analyses, buying basic equipment, and accessing bathymetry data and AUV instruments for further data collection.

The final key messages were that: a data system that supports the data organisation, management and sharing is fundamental; data need to be validated and quality checked before their use; metadata allow longevity and discoverability of the associated data; people should be trained and become familiar to GIS and Remote Sensing techniques as their application as analytical tools improves considerably the way of presenting geographic information and helps to make better decisions.

Although the workshop was very intense and stretched the full day, everybody had the opportunity to enjoy for one evening a local fish fry event close to a white sandy beach and turquoise sea. On Saturday the field trip to the pine trees restoration areas and to the nursery was guided by Naqqui, a real encyclopaedia of TCI plants and history, with the logistic support of Roddy, Luke and Kathrine. Finally, Sunday was time to relax on the wonderful beaches of TCI: sunbathing, swimming, bargaining the price of conch shells and then discovering afterwards that there were plenty on the beach!

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Integrating remote sensing imagery analysis with GIS: new perspectives for the Territories – South Atlantic region.

By iLaria Marengo

 In the South Atlantic region the use of remotely sensed images in environmental analyses should be considered more often. A couple of research projects are going to begin soon: one aims at using Landsat imageries to identify giant kelp in the sea surrounding the Falkland Islands. The project will be carried out with the support and expertise provided by the Welsh consultancy group Environment Systems. Freely available Landsat imageries and e-cognition (proprietary software) will be employed for the analyses and as a part of the project training will be provided to SAERI staff in order to acquire more confidence and skill in remotely sensed image processing and analysis.

The second project, led by the marine team in Saint Helena, includes the use of side scan sonar (starfish device) techniques to gather imageries, using acoustics, of the seabed in inshore waters around the island. The images, once analysed, should provide sound baseline information to derive, along with other data layers, n habitat map for inshore waters. An intense two day course was provided in the UK by CEFAS (Centre for Environment, Fisheries and Aquaculture Science), which delivers internationally renowned science (they have many years of multibeam and side scan sonar data collection, processing and analysis experience) and collaborative relationships with UK government, EU, NGOs, research centres and industry. Support from CEFAS will continue during the project and the process of mapping marine habitats is going to be carried out as well in Ascension and in the Falkland Islands, where a new fisheries department (Ascension) has been recently created and a new project on inshore fisheries (Falkland Islands), which is led by Dr Debs Davidson (SAERI), has just started.

The use of remotely sensed images has got two important advantages: spatially it is possible to cover large areas that with a manual survey would take long time. Temporally it is possible to have measurements of the same area at different and planned periods. Hence it is possible to detect which dynamics interest/affect a geographical area by looking at the spatial, spectral, radiometric and temporal properties of the sensor.

The integration of Remote Sensing to GIS would be advantageous for researchers working for the local communities of the South Atlantic region, however it throws up a few challenges. For example, the cost of very high resolution data (resolution <= 5 metres) and the partial coverage of free high resolution (between 5 and 30 metres) satellite images, such as Landsat, for the small and remote islands of this area of the Atlantic Ocean; the management of the amount and size of data collected; the complexity of the pre-processing phase of the overall image analysis process, which requires the use of proprietary software and high level of expertise.

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This last point is going to be addressed progressively. The goal is to build local expertise and skills in the use of Remote Sensing techniques, however initial support from external experts, such as Environment Systems and CEFAS, is essential to deliver the projects and to gain how to practically analyse remotely sensed data.

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