CC BY
59
УДК 528.91
Gottfried KONECNY
University of Hannover, Germany
ISSUES OF GEOINFORMATION
Key words: Geoinformation, Mapping, GIS
Summary
The paper summarizes the status and the issues of geoinformation (geodesy, photogrammetry, remote sensing, geoinformation systems, geoinformatics, cartography)
1. Background
1.1 What is geoinformation?
The ISO Bulletin, July 2001 states that at least 80% of public and private decision-making is based on some spatial or geographic aspects.
Geoinformation consists of digital spatial data in form of
- Maps (point - line - area data)
- Images (aerial photos, satellite images)
- Elevations (digital elevation models)
- Attributes (alphanumeric data related to points, lines, areas and defined objects based on geometrical data).
The information must be geocoded and accessible by metadata describing its contents.
To acquire geoinformation thus constitutes a multidisciplinary effort in which the traditional engineering disciplines of geodesy, photogrammetry and cartography for the creation of geocoded base data need to be merged with thematic content by the tools of remote sensing and field data collection involving a great variety of scientists from natural and socio-economic disciplines.
So that this becomes possible the relatively new tools of computer graphics and digital data base management need to be applied for the efficient display, manipulation, analysis and display of these integrated data.
1.2 Why geoinformation?
The UNCED Rio de Janeiro Conference of 1992 has for the first time coined the term of “sustainable development” in which the state of development of the world needs to be viewed in synergy, needs to be monitored, planned and administered in their natural and socio-economic environment in view of the present global trends. These are marked by a global population growth from 6 billion around the year 2000 until a predicted 8,5 billion in 2050 with a need of additional food production and the required needs for water and energy.
The population growth occurs particularly in urban centers of the developing countries which have an urgent need for the supply of infrastructure and the prevention of slum conditions. Paired with this population growth is the environmental degradation with a need to monitor the state of forests, the air and water pollution, crop yields, the drought areas, the waste lands and wet lands, the soil erosion and sedimentation, desertification, biodiversity and the danger of
floods and earthquakes, and the prospect of global warming. The developed areas of the globe suffer from an overaging of the population.
Other dangers to growth are caused by human factors, such as unsettled conflicts, diseases and last not least by corruption practices around the globe.
The geoinformation disciplines are not in a position to solve the world’s global problems, but they are able to make them transparent. The collected geoinformation data permit to offer tools to the global and local decision makers to change the global social climate of interference between nations in the 19th century and of the strive for independence in the 20th century to a need to recognize interdependence in the 21st century.
1.3 Traditional Approaches
The traditional approaches in mapping the world were handicapped by technology. While geodetic scientists established in the 18th and 19th century that a positional model for the earth was a rotational ellipsoid, the referencing of such a surface could only be done by local astronomic observations combined with triangulation. The height reference following gravity had to be independent from position. It was established by local tidal observations followed by spirit levelling. Obviously this resulted in different position and height datums for each country.
Topographic mapping by terrestrial means (plane table, stadia) because of the volume of the work became only possible in Europe. In other continents photogrammetry offered a solution in the 20th century. As a result a near global coverage at the scale 1 : 250 000 could be achieved. Local coverage at the scale range 1 : 50 000 to 1 : 24 000 was only possible for certain countries, such as the Russian Federation, all European countries, China, the continental USA, and India, while other countries are only partially covered at these scales. The coverage is particularly poor in Africa and Latin America.
Another aspect is the update rate of these maps. In 1990, according to the UN Secretariat the world average data of the map coverage 1 : 50 000 was only slightly less than 50 years. Based on these non-homogeneous maps thematic information was collected, but only few countries, such as Mexico and New Zealand issued country wide thematic maps at the 1 : 50 000 scale.
The available map archive was more recently brought first into raster digital form by scanning and then into vector form for GIS analysis.
1.4 New Technology
The recent advances in technology brought about a new potential to solve the mapping and map updating problem on a global scale. These advances are:
1.4.1 The GPS/DGPS technology:
The signals received from the 24 orbiting GPS (and also the GLONASS satellites) permit to determine a global position with 5 m accuracy by inexpensive code receivers or to better than 1 cm accuracy by more expensive phase receivers on a mass centered ellipsoid (WGS 84) by a network of observations. Since crustal movements of the earth surface exceed the cm-range this has prompted continents to establish their own earth centered reference ellipsoids (e.g. EUREF) with respect
to an international terrestrial reference frame ITRF tied to an epoch. For all practical purposes this has permitted a global georeferencing for data from different countries.
1.4.2 GIS
The tool for handling the georeferenced base map data and for merging them with the collected thematic information content for analysis has become the “Geographic Information System (GIS)”.
1.4.3 The Internet
The internet technology now permits the exchange of data between different suppliers, provided they meet standardized exchange options and formats, specified by the International Standards Organization (ISO TC211). For searches of relevant data and their quality metadata are utilized.
1.4.4 Satellite Images
To overcome the long production times to restitute aerial photographic images satellite images can now be used for fast mapping and map updating tasks, ranging from sensor systems at 15 m or 30 m ground pixel level, suitable for the 1 : 250 000 scale to sensor systems with 0,6 m to 1 m ground pixels, suitable up to the scale 1 : 5 000. These images can be supplemented by information from thematic sensors (imaging radar, image spectrometers).
1.4.5 Mobile Communication
Ground data collection is not only aided by the simple use of GPS code receivers, but also by modern mobile communication tools, which can utilize map and image portions in portable PC’s or PDA’s and which can transmit measured or coded data from the ground to data bases.
These phenomenal advances in technology and technology integration have brought about a new area in geoinformation technology.
2. Issues
While the availability of news is impressively visible at conferences and exhibits such as these, there are nevertheless a great number of issues, which need to be resolved:
2.1 Hardware
In the last 10 years the computer capacity has increased 100 times in speed, 1000 times in affordable storage and 5000 times in networking options. This has not only enabled faster computing, but it has permitted distributed computing with the inclusion of mobile and wireless options.
The platforms available now are server clusters, servers, desktop PC’s, laptops, tablet PC’s, PDA’s and cell phones. This has opened up a great number of new applications as real time GIS, as tracking analyst, as business analyst, as work management systems, and as emergency response systems.
2.2 Software
With the increase in computing power there is not any more the restriction to utilize computing time and storage capacity restrictions. The concept of a geocoded database for the display and the overlay of data layers with full topology and the advantage of using the topology for neighbourhood queries has become a reality. Obviously the tendency is toward web based solutions, where geodata may be accessed through geoportals.
2.3 Data Acquisition
Traditionally the data acquisition for new and updated information rested on a decision to acquire data either by ground surveys, from aerial photography or from satellite images. Now it is possible to combine such approaches, analyzing the costs and the time requirements for each work portion required. A few examples are listed:
1. In Dubai originally a photo scale of 1 : 5 500 for a municipal GIS was chosen, leading to a ground pixel size of 10 cm. This was done to be able to identify utility manholes. On the other hand, a photo scale of 1 : 13 000 is sufficient to update topographic features and buildings at a cost of 25% of the 1 : 5 500 scale using 20 cm ground pixels. But the manholes may more cheaply be ground surveyed by DGPS.
2. In Tirana there is the task to map and to update a 47 km2 urban area in a time period of only 6 months. The basic map 1 : 1 000 used for the Regulatory Plan was 13 years old. To update it with 1 : 5 500 or 1 : 13 000 aerial photography would have taken two years. On the other hand a 0,6 m pixel size of high resolution satellite images is sufficient to update buildings with ± 2 m accuracy at less than half the cost.
3. In Georgia a cadastral system needs to be established for the whole country. Orthophotos are displayed in personal computers. They are linked via bluetooth to DGPS rovers doing the measurements of boundaries to cm accuracy at the time of the adjudication procedures in the field. The total adjudication and survey process can be performed at a cost between 2 and 3 $ per parcel.
2.4 Data Updates
Whether a new survey or a data update is to be used depends on the number of features to be updated for a given area. Areas with high building activity may deserve a complete new mapping, which may be cheaper than the update of existing data.
What is to be considered further, is that previous digital maps have been collected as graphical CAD data. Instead of an object oriented topological data structure the digital map consists of points and lines only, and their meaning has been expressed by feature codes with limited intelligence. Moreover the number of feature codes used has been too numerous, so that it is difficult to update them. It is therefore advisable to limit the number of feature codes and to attach attributes to the features by using label points.
It is of interest that the presently available digital stereo photogrammetric workstations only offer very limited digitizing capabilities in 3D. 2D digitizing
often leads to practical difficulties to generate topologically structured GIS data from 2D, 2 ^ D or 3D measurements. Automatic data conversion into shape files can be done for most features, however a number of costly manual conversions still remain for GIS use.
2.5 Organizational Issues
Very often the existing organizational structures prevent an efficient integration of the data. Topography collected by photogrammetry, when referenced to a new control network and its extension by aerial triangulation can, for example, easily achieve dm-precision for cities.
Cadastral data are generally not visible in the images. Therefore the boundary measurements must be made independently on the ground, or they must be referred to visible points such as walls or fences. Or a local adjudication procedure must take place. The update of boundaries is in any case a sporadic issue following a transaction.
The responsibility for the survey of and the update of utility lines and utility features is in general an issue for the utility providers, which may accept relaxed geometric accuracy standards. But they are more interested in their network distribution with many attribute details.
Few cities have a satisfactory integrated mapping and GIS-system combining topography, cadastre and utilities. And if it has once been established, like in the KUDAMS project of Kuwait, it easily deteriorates, since the different organizations do not place sufficient emphasis on maintaining an integrated system.
2.6 Data Cost
Another handicap is the desire of the data providers to share the cost of their data acquisition and maintenance with the users. This is especially the case for the availability of large scale topographic data in European countries, where vector data are provided by official administrations, but they are too expensive to buy by general users. Even though the availability of base data in the USA is assured by the federal government at low cost, this is only done at small scales (1 : 24 000). The cost issue often limits the use and the value added data development by value added companies and users.
2.7 Data Security
Depending on the laws of a country some data providers are hesitant to issue data to the public because of security or privacy reasons. In this respect cadastral data are restricted in Germany. In Dubai an Internet site provided cadastral information to any user until recently the web-site ceased to operate for security or privacy reasons. Nevertheless the web-site has now been diverted from general Internet use to a governmental Intranet operation. Even then provisions must be made by encryption, so that Internet pages can only be read and changed by the authorized user.
2.8 Data Quality Control
In the compilation of integrated data from various sources many institutions face the problem of limited data quality. One of the best means to check data quality is to superimpose the digitized raster or vector data onto orthoimages produced from aerial photographs or satellite images.
Here the quality of the orthoimagery depends on the availability of a sufficiently accurate digital elevation model based on ground elevations. It is clear that displacements of building tops due to height will occur. When building heights are also acquired, it becomes possible to generate so-called “True Orthophotos”, for which the orthoimage generation is made at different levels according to a digital surface model. Current procedures to do this are, however, too costly to be considered for routine production, even though in research many attempts are under way to generate high accuracy digital surface models by laser scanning.
2.9 Digital Aerial Cameras
The standard aerial photographic film camera has provided a very satisfactory image product, which could be scanned for digital mapping, then performing aerial triangulation using inflight GPS and IMU data, the generation of digital elevation and surface models by image correlation, the production of orthophotos and their mosaicking into a seamless image data base.
The same may now be accomplished by digital mapping cameras. These have the advantage of better radiometric resolution (11 bit instead of 6 to 8 bit). They furthermore permit to record color images and infrared false color images at the same time. The disadvantage of digital cameras is that they are operated as normal angle and not wide angle cameras. Therefore the use of scanned analog aerial wide angle images is still of advantage in photogrammetric production. A scanning system, such as the Leica ADS 40 has a wider scan angle as compared to the Z/I DMC or the Vexcel Ultracam. It has the advantage, when flown with 60o lateral overlap, that it can gather all vertical facades of the area flown, avoiding gaps. Thus the platform has advantages for the production of flythroughs, should those be desired.
2.10 Geoportals
The Internet technology has made it possible to rapidly exchange geodata, provided that a fast communications network exists. Major administrations usually are connected by glass fibre lines. Even for Ethernet and broad bend connections the performance to access geodata in various remote databases are satisfactory.
The advantage of geoportals is that data may be in different formats, and that they may be modified (rectified and fitted) by use of geoservices in the net, making the user less dependent from intimate know-how of GIS systems. In Germany geoportals are under development for the exchange of data between the Federal Government Agencies and the State Administrations. Other portals are being created between state administrations and the local communities. Even the European Community develops a geoportal for data exchange between European countries.
2.11 Routing
A specialized GIS application lies in navigation, the routing and surveillance of transportation vehicles. Here again an integrated use of GPS technology for the location of vehicles and of GIS technology for the existence of a transportation network takes place. Fleets of delivery vehicles (taxis, delivery trucks, emergency vehicles) may be monitored and directed on the shortest available route.
There is an urgent updating problem for changes in the transportation infrastructure (changes in network, congestion, restrictions) which the data provider must overcome.
2.12 E-Government
Governments or other services have an interest to provide a service to the citizen or user to undertake transactions through the Internet without undue delays, avoiding unnecessary personal calls in different administrations to meet one objective, such as to obtain a building permit. e-government is the aim of most European administrations. It involves use of the GIS functionality. In Canada and in Dubai a number of e-government operations have become reality.
3. Conclusions
Humanity through its long history has undergone a transition from nomadic life to agriculture, to manufacturing and to service orientation. Now information and communications technology offers a new challenge in development.
The provision of geoinformation is part of this scenario, which can and must be used to overcome current global shortcomings.
One of the oldest philosophical books, written in the 4th century in Southern India, the Kural, suggest to us the geoinformation community:
- “Do not look at past accomplishments, but look at what you can do for society today.”
Our geoinformation disciplines should work together to meet this challenge.
REFERENCES
- UN (1992): Report of the United Nations Conference on Environment and Development-
Rio Declaration, www.un.org/documents/ga/conf151/aconf15126-1annex1.htm (1.12.1004)
- UN Secretariat (1993): The Status of World Mapping 1990, World Cartography,
United Nations Cartographic Conference, Beijing, Paper prepared by A. Brandenberger
and S. Ghosh
- Seeber, G. (2000) Satellite Geodesy: Foundations, Methods and Applications, De Gruyter,
Berlin, ISBN 3-11-012753-9
- Linder, W. (2003) Digital Photogrammetry, Springer Verlag, Berlin, Heidelberg, New
York
ISBN 3-540-00810-1
- Groot, R. and McLaughlin, J. (2000) Geospatial Data Infrastructure, Oxford University Press, New York, ISBN 0-19-823381-7
- Bill, R. (1999): Grundlagen der Geo-Informationssysteme, Wichmann Verlag, Heidelberg
- ISBN 3-87907341-4
- Bartelme, N. (2000): Geoinformatik, Springer Verlag, Berlin, Heidelberg, New York, ISBN 3-54065988-9
- Konecny, G. (2003) Geoinformation: Remote Sensing, Photogrammetry and Geographic
Information Systems, Taylor and Francis, London, ISBN 0-415-23795-5
© GottfriedKonecny, 2005
