Imperatives of faster updating of data and demands from new users
are egging the national mapping agencies to move towards new
technologies and processes.
By Prof Arup Dasgupta
In the September edition, we discussed the policy issues confronting the National Mapping Agencies (NMAs). Policy issues are usually intertwined with technology advances. Given that surveying and mapping has been around for centuries and the mandate to create authoritative data for a country rests on the NMA, it is but natural to rely on time-tested technologies. However, imperatives of faster updating of data arising from growing demands as well as demands from new users often catalyses the need to move to new technologies and processes. Beginning with the basic concept of baseline datasets changes are happening in the way data is acquired, stored and distributed.
All geospatial activities require baseline datasets which are usually provided by the NMAs. In Japan, it is called Fundamental Geospatial Data defined in a law dealing with NSDI issues established in 2007. In Norway, there are many baseline datasets at different levels of usage. Low level for datasets and databases, middle level for services, which uses or are based on the databases and datasets, and high level for simple public services such as portals, websites etc. which use the services. While all these layers of distribution are available for the users, it is ensured that the private companies retain their market for more advanced geospatial products.
The Ordnance Survey of the Great Britain also has a similar approach based on ‘fitness for purpose’. While a 30 second or 1km digital elevation model (DEM) grid such as the NOAA’s (National Oceanic and Atmospheric Administration) Globe 30 is fit for many purposes, a developed nation such as the Great Britain has many needs that require far greater detail and integrated geographic products of which height is only one component. The Dutch Kadaster is responsible for the key registers on topographic and cadastral data in the country. These registrations are part of a national system of Key registers, defined by national law.
Developing countries also have baseline datasets, courtesy of their colonial heritage. Sri Lanka has maps at 1:50,000 and 1:10,000 scales, geodetic control and cadastral data as authoritative data. Survey of Bangladesh prepares base maps covering the whole country. Thus baseline dataset that includes number of feature classes, are automatically inserted into the authoritative data. The National Mapping and Resource Information Authority in Philippines, abbreviated as NAMRIA, produces topographic base maps, nautical charts and other fundamental thematic maps such as land cover and land classification. These are all part of a good baseline dataset along with fundamental data being produced by other agencies like cadastral data, public infrastructure, environment and natural resources, etc, points out Efren P. Carandang, Deputy Administrator, National Mapping and Resource Information Authority, Republic of the Philippines. Republic of Korea has the basic geospatial dataset which acts as a reference to other dataset, as mandated in the Korean National Spatial Data Infrastructure Act, reveals Sanghoon Lee, Team Leader, International Cooperation and Standard Team, National Geographic Information Institute.
In Malaysia, JUPEM has a complete baseline dataset covering the core cadastral and topographical or built environment datasets which are recognized nationally as the fundamental datasets of their national data infrastructure (NSDI) and are the ones that are needed by other governmental agencies. Mexico also has a very detailed dataset at 1:50,000 scale.
VGI as a data source
One of the most disruptive technologies is the GPS-enabled smart phone. Common people can now locate their PoIs and share them through the Internet. While the accuracies are low, of the order of tens of metres, the value lies in the timeliness of the data. In disasters and other fast-changing situations such data is invaluable. Google India attempted to update its maps of India through a Mapathon where individuals were encouraged to locate PoI.
This was unfortunately undermined by Survey of India, which restricted the data dissemination pending vetting for ‘sensitive’ locations. While this was an extreme reaction but not unique to India. Some other countries however, are more forthcoming, albeit with caution. Dr Hiroshi Murakami, Director-General of Planning Department, Geospatial Information Authority of Japan (GSI), agrees that volunteered information is potentially useful for detecting changes. However, due attention has to be paid to the quality of the information provided by volunteers. For example, to revise mountain trails, which tend to change due to landslides, training on GPS is provided to volunteer mountaineers who provide the mountain trail data as they climb. The NMA assesses the data and uses it to update its database.
Norway also relies on public reporting of errors or missing elements in a map through a website, to manage some datasets which need frequent updating. Quality assurance is done and if the error is genuine, the authoritative databases are corrected, says Anne Cathrine Frøstrup, Director General of Kartverket, Norway. In the Netherlands, VGI is used for specific data. For example, as Kees de Zeeuw, Director Kadaster International, points out, the monitoring of the international border poles in the Netherlands is done with the aid of mobile services and the public.
Peter ter Haar, Director of Products and Innovation, Ordnance Survey, thinks volunteered or crowd sourced data has its place, but at present it is not authoritative or consistent enough. There are question marks over its reliability and accuracy, and with many crowd sourced datasets they are incomplete.
Sri Lanka is planning to update its 1:10,000 scale maps with VGI. All the Survey department staff, including non-technical staff and students, will be asked to add missing or new data for a small area where they live. Validation would be done by a surveyor at the mapping branch in the same area using satellite images. This could be expanded to the young school student’s in future in a digital environment, maintains P. Sangakkara, Additional Surveyor General (Central), Sri Lanka. The Philippine Geoportal provides a platform for sharing and integration of such datasets into authoritative government datasets for any specific or general purpose. The outputs of such integration remain separate from the core authoritative datasets and the responsibility for such outputs rests with the contributing entity. However, Bangladesh and Malaysia do not use VGI because of lack of authenticity. They may use it in the future under an appropriate policy.
South Korea is considering VGI for real-time updating of specific areas, and establishing a prototype VGI-based GeoPortal for disaster management as a mission of UN-GGIM-AP WG2. The country would in particular like to adopt the concept of community mapping by trained community members with NMAs’ support for tackling quality concerns.
In the case of INEGI in Mexico, there are efforts such as Participatory Mapping project, through which the organization aims to capture updated information with the active participation of the public, the state units and the academy. Comments received from the public are sent to the units responsible of maintaining this information, who will then validate the updates and reflect them monthly on the central database.
Common geodetic framework
Tracking and control of launch vehicles and satellites do need a global geodetic network. However, why do we need such a global network for what is essentially national or regional tasks? According to Dr Murakami, using a globally common geodetic framework is the most accurate and efficient way of developing the country’s geodetic framework. Traditionally, a framework was developed by doing local astronomical observations and ground survey by setting up monuments on the ground, or extending the framework of the neighbouring countries.
However, this methodology has inherent problems of error accumulation geographically and limited temporal resolution as it takes a long time to complete the survey. The introduction of VLBI and GNSS and other space geodetic technologies and the wide-spread commercial applications of satellite positioning, has energized the geodetic framework. It requires close international cooperation on the observations. In addition, the earth is changing its shape continuously. Therefore, globally consistent continuous geodetic observation is the only way to create accurate and stable geodetic framework even for local and regional areas.
Frøstrup adds that location services-based on GNSS have totally changed the way of positioning things, making it a necessity to have a geodetic reference frame that covers the entire planet. “Ultimately, we need one global geodetic reference frame maintained on the global level, but densified to improve the local accuracy on regional or national level,” she says. Peter ter Haar adds that satellite positioning is obviously a global system and therefore requires a globally consistent geodetic framework within which to operate. A global geodetic system is also very important for scientific activities involving Earth monitoring.
Creating common geodetic framework
Japan works closely with the international organizations on very-long-baseline interferometry (VLBI) and GNSS observations, and provides data to them. The results of such international observations are processed, analysed and combined to develop a global geodetic framework, which is adopted for the national geodetic framework by connecting all national control points to coordinates of the origin realized by the international cooperation together with the ellipsoid to translate the 3D coordinates into latitude and longitude, says Dr Murakami.
In terms of update, the initial framework is retained as the standard framework for a 30 or 40 years, until the displacement caused by ground surface movement due to the plate movement and earthquakes becomes significant. In case of large local displacements due to earthquakes, only coordinates of control points in the affected areas are revised in each case.
However, when a devastating earthquake hit the eastern Japan in 2011, the ground surface movement was more than 5 meter, and complicated, requiring updating of the framework. The framework of north-eastern half of Japan was updated to ITRF2008 based on observation of VLBI, GNSS and geodetic levelling. The other half of Japan still adopts ITRF94, because the area experienced only small displacement and the amounts do not have much social influence.
Norway has for decades been operating a geodetic observatory at Svalbard. With its location at 9 degrees north, the observatory plays an important role in the determination of polar motion that is essential for the operation of satellite navigation systems. The Norwegian government decided in 2011 to upgrade the observatory into a so called “core site” which means that the observatory should be equipped with state-of-the art technology within all the geodetic disciplines. The observatory will become one of the key pillars of the global geodetic reference frame when it’s finished in 2020, reveals Frøstrup.
The Norwegian geodetic network is aligned to the global geodetic network but fixed to earth crust as it was in 1989. “By using a network of about 150 continuous operating GNSS sites, we are monitoring the difference between the national and the global reference frame. The difference is transmitted as a national service to professional GNSS users so that they becomes able to perform positioning in accordance to the national geospatial infrastructure,” she adds.
The primary geodetic coordinate reference system in Great Britain is realized by the Ordnance Survey’s nationwide network of permanent high precision GNSS receivers — OS Net. OS Net realises coordinates in the European ETRS89 (European Terrestrial Reference System 1989) which is a consistent, GNSS-compatible, geodetic system applicable across the whole of Europe and is used to enable compatibility of positioning and geo-data across the entire continent. ETRS89 is also directly related to the global ITRS (International Terrestrial Reference System). So, if required, ETRS89 coordinates in GB can be easily transformed to coordinates in the global ITRS.
Data in Sri Lanka is now in geodetic reference GN99, which is well documented and transformation is included in most GPS receivers. Hence data can be converted to WGS84 or vice versa. The Survey of Bangladesh has already integrated the coordinate system from local (Everest 1830) to global (WGS 1984). At present the reference framework used is ITRF-1992, which is going to be transferred to ITRF-2008 very soon and necessary GNSS observations are already done, reveals Surveyor General of Bangladesh Brig Gen Md Abdul Khair.
In line with its mandate to establish and maintain the national geodetic network and pursuant to UN General Assembly Resolution 69/266, NAMRIA formulated and has just started implementing a national geodetic network modernisation plan. Malaysia too is updating its geodetic framework to link it to the world geodetic framework, adds Datuk Sr Ahmad Fauzi bin Nordin, Director General of Survey & Mapping.
Open data standards
The Japanese government has developed its own open data standards on the government data available on the web, and GSI complies with the government standards. Norway follows the open data standards, and the ISO TC 211 standards and specific domestic standards. Ordnance Survey introduced persistent identifiers in their Boundary-Line product, and then in OS MasterMap in 2001. It also encouraged the Digital National Framework (DNF). However, a large group of users simply want to combine their data with ‘a map’, and OS supports this through OS OnDemand (an open standard INSPIRE View Service, which is in itself an Open Geospatial Consortium (OGC) Web Mapping Service) and OS OpenSpace (a simpler interaction with a web API, suitable for consuming in websites). Since 2010, OS data products are published in GML 3.2. In the past five years, OS has pioneered providing geospatial data in ‘linked data’ format. The Netherlands complies with legislation and international law while treating user demand as the focus.
Both Sri Lanka and Bangladesh are in the process of evolving open data standards based on ISO specifications. In Philippines, using a common set of base maps, geoportal data contributors and users, as well as those working independently outside of the geoportal system, are assured that whatever maps and datasets they produce are interoperable with one another.
The way ahead
The impact of new technologies and processes are being felt as NMAs adopt them, in some cases with caution. However, the pressure of demand and the evolution of new applications, particularly individual based applications is and will continue to foster change. Here again the success or failures of NMAs are being dictated by their ability to see the future and adapt and adopt.