Hesham N. Al-Telaihi, Fuad S. Al-Aqeel and Waleed K. Al-Jassim
Kuwait Municipality Survey Department, P.O. Box 10 Safat, 13001 Kuwait
[email protected]kmun.gov.kw, [email protected] and [email protected]
Inst. of Photogrammetry and Geo-Information, Univ. of Hannover, Nienburger Str. 1, 30167 Hannover, Germany
Topographical line mapping organised by Kuwait Municipality Survey Department (KMSD) is based on air photos and a standardised list of 70 features. A wealth of topographic base map data is available at KMSD, predominantely stored in a CAD data model. PHOENICS GmbH has converted CAD data of a test area in Kuwait into a GIS environment, and has generated a set of advanced vector-based and raster-based geo-data products, including a Digital Terrain Model (DTM), a Digital Terrain and Building Model (DTBM), Digital Orthophotos (DOPs), an orthophotomap, and a landuse map. The DTBM in particular is a useful database in planning telecommunication antenna networks for highly developed inner-city areas. In the telecomm industry DTBMs are used in analyses of line-of-sight and visibility, radio signal propagation studies, and antenna network optimisation projects. In combination with other data layers, such as a digital orthophoto mosaic or a landuse map, DTBMs are used in visualisation studies and 3D-flythroughs. Such animations are frequently designed in architectural planning. Examples of possible applications of geo-data products are shown. Advanced geo-data products generated from KMSD air photos and line mapping data shall help to expand the range of geo-data applications and users in Kuwait.
In the evolution of Geographic Information Systems (GIS) a tendency arose that a base map is the backbone of a GIS, and should be established first. The base map frequently is a topographic map, which shows the visible features of the Earth’s surface, often including a Digital Terrain Model (DTM) to describe the distribution of its elevation (Konecny, 1997). Photogrammetric line mapping is the classical way to obtain the topographic base map. Additional official thematic maps often include a cadastral map and a map of utilities.
Kuwait Municipality Survey Department (KMSD) is the organization in charge of official mapping for civilian purposes in Kuwait. KMSD and its photogrammetric contractors have compiled line maps by stereo compilation from aerial photos since the 1970s. Early line maps were geometrically inaccurate as a result of discrepancies in the geodetic network they were based upon. In 1980, the setup of the New Geodetic Network of Kuwait (N.G.N.) and the so-called Kuwait Utilities and Data Management System (KUDAMS) project were started. KUDAMS was a large-scale utility management project derived from field survey and aerial photography, implemented on Intergraph equipment basically as a Computer Aided Design (CAD) system for access to public utility data (Al-Jassim, 1996 and 1997).
The KUDAMS project was near completion when it was brought to a complete halt by the Iraqui occupation of Kuwait on 1 August 1990, but KUDAMS topography and utility data were stored in duplicate at the Japanese premises of a contractor involved in the project. After the liberation of Kuwait (21 to 25 February 1991) the system was recovered and re-installed in 1991 / 1992 by a Municipal Committee under the Director of Surveys (Konecny, 2005).
Decisions of the committee included separation of efforts between the Ministry of Justice (MOJ) and Kuwait Municipality. KMSD was assigned the task to maintain the records of topography and the cadastral map. Within KMSD, the Survey Data Section is responsible for photogrammetric work, cadastral mapping, and continuation of any KUDAMS activities. Map information is stored in Microstation J software (by Bentley). As was introduced during the KUDAMS project, the Survey Data Section generates and updates three basic maps, closely following general GIS data and mapping concepts for setting up a National Spatial Data Infrastructure (NSDI):
- the cadastral map,
- the topographic base map, and
- the map of utilities.
The KMSD cadastral map contains international state boundaries and boundaries of the Kuwait Governorates. Within these administrational units the land is subdivided into neighbourhoods (Mantiqa), blocks (Qita’a) and land parcels (Qaseemah). Cadastral attributes are the parcel number, the parcel area (in square meters), and a remark making reference to the cadastral map. Attributes are stored in Microsoft Excel format spreadsheets for every parcel, but are not linked to the graphical data. Cadastral updates are introduced into the map (dgn-file) against the background of Digital Orthphotos (DOP). The respective spreadsheet is updated subsequently. The cadastral register and ownership information is kept at the MOJ.
Fig.1: Subset of a KMSD topographic base map.
While the cadastral map is confidential, the KMSD topographic base map (Fig. 1) is open to the private sector. The base map is generated from air photos following a catalogue of 70 different features (Hermsmeyer et al., 2005). It is stored in 3D dgn files at 1: 500 map scale and includes terrain and building elevation, as well as connective street centre lines, separated by nodes at street intersections. Topographic map information is disseminated to third parties in AutoCAD or Microstation file formats. The topographic base map represents features with points, lines, polygons and text of different colour, size and style.
The map of utilities contains information on fresh and brackish water pipes, sewer and storm water systems, high and low tension electricity cables, telephone cables, and street lights. Information for the utilities map is not collected by KMSD, but is provided by other organisations, including the Ministry of Power (MOP, formerly the Ministry of Electricity and Water). As KMSD has little influence on data deliveries from other organisations the map is presently incomplete.
Overall, a wealth of standardised, recent and geometrically accurate topographic data exists in Kuwait as a result of the KUDAMS project and regular succeeding updates of maps at KMSD.
Today the data is used in organising the Kuwait cadastre efficiently, but the country also has a long history of planning based on geo-data. The First Kuwait Master Plan of 1952 laid down essential principles that have been followed since. The second version of the Kuwait Master Plan was stopped by the Iraqui occupation (as was the KUDAMS project), but in 1992 a wholly new Third Kuwait Master Plan (3KMP) was prepared. This plan was completed around 1997, and GIS technology (based on Arc/Info and ArcView by ESRI) was embodied as an integral part. In planning it is critical to ensure that day-to-day decisions, made as part of the on-going land development process, are consistent with interrelated issues and actions as addressed by the overriding Master Plan, such as infrastructure capacity, adequate provision of public facilities and services, transportation, socio-economic development, etc. In implementing 3KMP, the GIS installation was seen as a pilot project for a Kuwait national GIS, designed for flexible operation and incremental expansion as needed. It was recognised that GIS data provide a most useful means to interrelate the two levels of planning (day-to-day decisions and the Master Plan), as well as the co-operation between different Ministries and organisations involved in land development and management (Al-Jassim, 1996 and 1997).
The KMSD topographic base map also provides a sound foundation for implementing private industry applications fast. For example, connectivity of street centre lines allows for implementing traffic and routing applications, such as used in car navigation. In a previous paper (Hermsmeyer et al., 2005) we have shown how PHOENICS GmbH has derived advanced geo-data products, including a Digital Terrain Model (DTM), a Digital Terrain and Building Model (DTBM), Digital Orthophotos (DOPs), an orthophotomap, and a landuse map, from KMSD air photos and and topographic base map data.
In this presentation we will show how KMSD topographic base map data can be processed to derive DTBMs (or 3D city models), and how DTBMs are used in telecommunication applications, environmental studies, and Computer Aided Architectural Designs (CAAD) to the benefit of highly developed inner city areas.
Objectives of this paper are
- to explain how KMSD topographic base map data is processed in order to generate a DTBM, and
- to show examples of how DTBMs are used in technical applications and planning, e.g. by the telecomm industry, in environmental studies on the propagation of air pollutants or noise, and in CAAD.
Material & Data
Test data from the KMSD topographic base map is used to demonstrate data processing for the generation of a 3D city model (DTBM) of Kuwait. DTBMs and projects from other cities, selected from the PHOENICS GmbH archive, are used to demonstrate model applications.
As test data, one sheet of the KMSD topographic base map, covering 1 km by 1 km of urban residential area in flat terrain, is selected from a recent line mapping project. The following data is used:
- digital scans of 14 mm resolution, of three colour aerial photographs (two stereo-models), taken consecutively in east-western direction at an image scale of 1: 6.000 with an overlap of 60%, using an aerial survey camera with a 302.98 mm focal length lens. Scans were stored in compressed TIFF format, including image pyramids, with a radiometric resolution of 24 bits (8 bits per colour channel),
- calibration data describing the camera and lens, including co-ordinate information of eight fiducial marks,
- orientation parameters of the air photos (from aerial triangulation calculation),
- vectorised topographical data from stereoscopic line mapping, stored in dgn file format (CAD data model),
- the standard KMSD line mapping feature code list.
DTBMs of the German Cities of Bremerhaven and Dachau are selected from the PHOENICS archive to demonstrate possible DTBM applications.
DTM: A DTM of the Kuwait test area (excluding buildings, structures and vegetation) is generated. To derive the DTM, the KMSD topographic map data is transfered from the CAD system into a GIS environment (ArcGIS by ESRI). Features containing elevation information are selected from the vector data. A Triangulated Irregular Network (TIN) is generated from cell (i.e., point) features (spot heights, traffic light base heights, high tension tower base heights, and manhole heights), and line features (5 m and 1 m contour lines). A regular grid DTM of 2 m cell size is derived from the TIN.
3D City Model: To generate the Kuwait test area DTBM, the air photo stereopairs and image orientation data are imported into stereo analysis software. Using stereo glasses controlled by an infrared emitter for stereoscopic viewing, roof top elevation is measured for every building according to the following specifications, which are developed by PHONICS GmbH in co-operation with vodafone D2 GmbH for telecomm applications in Germany:
- Roofs composed of sections larger than 5 m2 are separated when the elevation difference between sections is 2 m or more. One elevation value is stored with every roof section.
- If more than 50% of a roof is covered with roof top assemblies (water tanks, elevator shafts, etc.), the elevation of the assemblies is measured and is assigned to the entire roof.
Values are stored as absolute (above sea level) and relative (above terrain) elevation.
A Digital Orthophoto (DOP), an orthophoto map and a landuse map of the Kuwait test area are also produced. The applied methodologies and results are described in Hermsmeyer et al. (2005).
3D-flythrough animations: Flythroughs are generated from the orthophoto mosaic, landuse map, and DTBM using animation software. Results are stored in Audio Video Interleave (avi) file format.
Several animations of increasing photo-realistic appearance are generated, using (i) the DTBM and landuse map, (ii) the DTBM and orthophoto-mosaic, and (iii) the DTBM, orthophoto-mosaic and terrestrial photographs of building facades and vegetation. To visualise facades photo-realistically, terrestrial photos of facades are rendered randomly on the vertical ‘walls’ of the DTBM.
Various mathematical algorhithms and software products are used to compute line-of-sight, visibility, mobile phone signal strength, air pollutant distribution, or noise propagation with use of DTBMs. Visualised results of such computations are shown in this presentation to demonstrate possible DTBM applications, but computational algorithms are not discussed. Information on the methods applied is available through PHOENICS GmbH upon request.
Results & Discussion
Kuwait test area results:
DTM: The Kuwait DTM grid (cell size 2.0 m, 500 rows x 500 columns, Xmin: 514,000.00, Xmax: 515,000.00; Ymin: 205,000.00, Ymax: 206,000.00) is shown in Fig.2. The terrain is almost flat, with some road embankments visible in the northern part. The highest point is at 37.63 and the lowest point is at 24.00 m above sea level; average elevation is 30.44 m. We list these values to demonstrate possibilities of numerical applications, such as those described below.
3D City Model: The Kuwait DTBM is shown in Fig.3. A cell size of 0.5 m is used to conserve sufficient building details for DTBM applications. The model fulfils criteria as required by the telecomm industry.
In Fig.4, a subset of the DTBM is shown, superimposed with building polygons from the vector data (manually subdivided and with corrected elevation). Dark yellow polygons represent low, and bright polygons represent high buildings. Lengths of building shades correspond to building elevation.
The DTM and DTBM of the Kuwait test area fulfil telecommunication industry criteria as listed in the methodology section of this presentation. In the following section we will demonstrate examples how comparable elevation models of other cities are used in a number of different applications. The Kuwait DTM and DTBM can be used in similar applications.
Fig.2: Grid DTM (shaded relief view) of the Kuwait test area with automatically generated contour lines (values in m above sea level). Top is north.
Fig.3: DTBM (shaded relief view) of the Kuwait test area.
Fig.4: Enlarged subset of the DTBM (grey-scale shaded relief view), superimposed with building polygons.
Examples of possible DTM and DTBM applications:
GSM base station visibility: Planning GSM (Global System for Mobile communications) and comparable mobile communication antenna networks is an important application of 3D city models. Telecomm companies realise the bulk of their business and turnover in highly developed urban areas where high rising buildings are common. Mobile phones never communicate directly with each other, but through the closest base station of an antenna network. GSM signals travel best along visible lines between the closest base station and the mobile phone, but signals are absorbed and reflected by building materials. The aim of antenna network planning is to minimise areas with no reception, i.e. areas shaded by edifices from base station visibility, while minimising areas of signal overlap to reduce network operation and maintance costs. An example from the City of Bremerhaven in Germany is shown in Fig.5 (a and b). Proposed base station locations are in the centres of the two circles, 1 and 2 (Fig.5a).
Fig.5, a: Modelling GSM base station visibility in a DTBM (2D view, image by PHOENICS GmbH).
Fig.5, b: Modelling GSM base station visibility in a DTBM (3D view, image by PHOENICS GmbH).
Base station network planning is carried out with use of DTBMs. Co-ordinates (X, Y, and Z) of the proposed base station location are selected in the 3D city model, and a circular buffer is defined around the location to describe the area covered by the station. Spatial trigonometry is applied to determine DTBM raster cells inside the buffer visible from the proposed location. A colour code is assigned to all visible cells. An offset of the base station over the roof top at its proposed (X,Y) location can be described by increasing the Z-co-ordinate, simulating the effect of a base station mast.
More advanced models of GSM signal propagation take into account the flux density of the signal field strength (indicated in Watts per meters square). Signal strength does not break down rapidly when a buffer area around the base station is left (as is suggested in Fig.5), but rather it decreases continuously as the distance from the base station increases. In combination with signal absorption and reflection on building materials in urban areas, this results in a geographical distribution of signal reception which is more complex than suggested by base station visibility alone. An example from the City of Dachau near Munich in Southern Germany is shown in Fig.6.
Fig.6: Modelling GSM signal strength in a DTBM (image courtesy of enorm GmbH).
Distribution of air pollutant concentration and noise: Car traffic is often dense in urban areas, and causes emissions of noise and air pollutants (dust particles, carbon-particulate matter, nitrogen oxides, etc.). Objectives of planning an urban road system should be to direct car traffic efficiently (i.e., to minimise traffic congestions) while keeping through-traffic away from residential areas and densely developed inner cities. For new settlements and extensions of the road system the amount of pollutant emissions can be estimated from expected traffic densities (number of cars or trucks per hour). For existing roads, emissions can be estimated from traffic census. Numerical algorithms and computer software are available to calculate pollutant concentrations and noise levels under various atmospheric and wind conditions. Pollutants have a tendency to accumulate in “urban canyons” along narrow streets between buildings. Therefore DTBMs need to be included in computations of concentration distributions. An example is shown in Fig.7.
Fig.7: Modelling air pollution caused by car traffic using a DTBM (image courtesy of GeoNet Environmental Consulting GmbH).
Computer Aided Architectural Designs (CAAD):
From around 1950 to the year 2005 Kuwait has developed from a small mud brick town of 75,000 to a contemporary metropolis with a population of about 2 million (Al-Jassim, 1996 and 1997). Many cities in the Gulf area have similar growth rates, posing serious challenges to architects and urban planners. When new buildungs and settlements are planned, buildings already existing around the construction site should be taken into account. Existing buildings are included in DTBMs, which can be altered to also include the dimensions and elevation of the newly planned buildings. Terrestrial photographs of building facades can be rendered onto the ‘walls’ of edifices in the DTBM, and Digital Orthophotos (DOPs) can be used to visualise the street level around the buildings. The result is a photo-realistic, virtual visualisation of the real-world situation of the construction site and its surroundings, which can be presented to decision makers and construction principals to give them a visual impression of the proposed architectural design. Architectural computer models using DTBMs help architects and planners to compare visual effects of different planning alternatives, and to save time and costs of planning by reducing the number of field visits to the construction site required during the planning phase. Computer animations software is used to generate walk-through or fly-through animations, which enable visibility of the planning area from all sides, including bird’s eye perspectives which in the real-world can only be achieved with expensive helicopter rides – an option hardly applied in architecture and urban planning.
Figure 8 (a and b) shows screenshots of 3D-flythroughs from the Kuwait test area. Building facades and vegetation are rendered into the DTBM. In Fig.8a (left image) the orthophoto mosaic of the test area is used to visualise street level. In the right image (Fig.8b), the landuse map is used.
Fig.8: Screenshots from 3D-flythrough animations of the Kuwait test area.
Only five different terrestrial photographs of Kuwait building facades are repeated over the DTBM building walls in Fig.8. Although these ‘synthetic facades’ already provide a photo-realistic impression of the real-world situation, this impression can be much enhanced when terrestrial photos of the real facades are used. An example is shown in the following Fig.9 (a and b), which uses a DTBM and terrestrial photographs of real building facades of the City of Bremerhaven in Germany.
While in most cases of DTBMs covering large geographical areas it will be too expensive to use terrestrial photos of real facades for animations, this may be an option for limited geographical areas which are frequently looked at in Computer Aided Architectural Design for individual buildings or smaller settlements.
Fig.9a: DTBM for Computer Aided Architectural Design (by PHOENICS GmbH).
Fig.9b: DTBM and photo-realistic facades for Computer Aided Architectural Design (by PHOENICS GmbH).
A wealth of up-to-date, accurate, and consistent geo-data exists in Kuwait, predominantly as a result of the KUDAMS project and succeeding, regular data updates at KMSD. The data is well prepared, and the topographic base map is diclosed in CAD file formats for private industry uses. Relatively small alterations of the data, such as data transfer into a GIS environment, and a review of elevation information, open access to a large number and variety of possible data applications. Street centre lines may be used in traffic routing (car navigation). Elevation information is appropriate to generate Digital Terrain Models (DTMs) and 3D city models (Digital Terrain and Building Models, DTBMs). DTMs and DTBMs are useful base data for applications in telecommunications, air pollutant and noise modelling, and Computer Aided Architectural Designs.
The example of the Kuwait test area 3D city model shows that both the topographic base data (as part of a National Spatial Data Infrastructure of Kuwait) and the software technology exist for use in private industry applications. The examples presented of such applications show how topographic base data can help to direct the rapid development of Kuwait City according to the guidelines of the Kuwait Master Plan.
Present difficulties at KMSD to complete the Kuwait utilities map, which is believed to become another very valuable map for private sector activities, are mainly caused by organisational challenges. There is hope that these challenges can be overcome in the context of the E-government initiative, which was recently announced by the Kuwait government executive branch during the Kuwait Info-Connect 2005 exhibition (5 to 11 February 2005). Kuwaiti organisations participating in the initiative include the Ministries of Interior, Education, Justice, and Health as well as the Kuwait Civil Service Commission, the Kuwait Public Authority for Civil Information, Kuwait Municipality, and the Kuwait Institute for Scientific Research (KISR).
- Al-Jassim, W.K. 1996. New master plan for Kuwait. Paper presented at the 1996 ESRI User Conference, 20 to 24 May 1996. Wyndham Hotel and Convention Center, Palm Springs, California / USA. Available on the Internet under https://gis.esri.com/library/userconf/proc96/TO350/PAP331/P331.HTM (verified 03/16/2005).
- Al-Jassim, W.K. 1997. Dynamic planning using GIS: the Kuwait experience. Paper presented at the GIS/GPS Conference held in Doha, Qatar, March 1997. Available on the Internet under www.gisqatar.org.qa/conf97/links/p10_e3.html (verified 03/16/2005).
- Hermsmeyer, D., H.N. Al-Telaihi, F.S. Al-Aqeel, M.H. Guretzki and G. Konecny. 2005. Advanced geo-data products from Kuwait Municipality Survey Department air photos and line mapping data. Accepted for publication in [email protected] Middle East, May / June 2005 issue.
- Konecny, G. 1997. Potential of GIS in the GULF-Region. Paper presented at the GIS/GPS Conference held in Doha, Qatar, March 1997. Available on the Internet under www.gisqatar.org.qa/conf97/links/p13_l1.html (verified 03/16/2005).
- Konecny, G. 2005. Creation of a national cadastre map of Kuwait at Kuwait Municipality. Paper presented at the Kuwait 1st International GIS Conference and Exhibition, 05 to 07 Feb. 2005, Crowne Plaza Hotel, Kuwait.