Cornput., Environ. and Urban Systems, Vol. 17, pp. 223-229,1993 Printed in the USA. All rights resewed.

0198-9715/93 $6.00 + .oO Copyright Q 1993 Pergamon Press Ltd.

PHOTOGRAMMETRY AS A COMPONENT OF GEOGRAPHICAL INFORMATION SYSTEMS

CART0HANSA Kft., Budapest, Hungary

ABSTRACT. After outriding the deve~pment in photogrum~tric plotting devices over the last 15 years, various stages in the development of infor~~ation systems and their kicking-up to different photogrammetric systems and ideas will be discussed The second part of this paper considers the change that has taken place in the working procedures used in photogrammetric data capturing and the resulting effects upon production techniques.

INTRODUCTION

Although research in the traditional area of photogra~c~y and its Iink with the digital cap- turing of data had already reached a very high standard more than a decade ago and research institutes had rapidly advanced into new areas such as digital image processing and robot vision, over the last few years, users have experienced rapid changes in the technical equip- ment now being offered by system m~ufacturers. The impetus for this clearly came from the computer industry and in particular from the field of computer aided design (CAD) and database technology.

The effects of technological developments in the field of CAD upon photogrammetric users will therefore be outlined below. An essential element is the signi~cant role of photogramme- try in the establishment and maintenance of Geographical Information Systems (GE).

Photogrammetric data capturing (above all, of aerial photos), aims to provide both geometric information - here essentially extracting information about the topography of the earth’s sur- face - as well as thematic information such as land-use development patterns. Up until about 10 years ago, such information was presented almost entirely in the form of analogue map series. The development of computer-assisted photogrammetric stereo plotting started at the

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223

224 R. Sc~fofb, i-i-13. Amo~d, and J. ffi~g~ofer

end of the 1970s in order to refine the production of such maps. This computerisation mainly concerned controlling the operation of automatic drawing tables such as the Avioplot RAP sys- tem produced by the company WILD (Heerbrugg, Switzerland) or the COGRA system by Dietrich (1980). Most systems designed for stereoplotting devices did, of course, contain mod- ules for calculating and supporting model orientation. Analytical plotting devices also con-

tained integrated graphic software modules. These techniques led to a significant increase in productivity but frequently did not replace the task of manual final drawing.

At the beginning of the l%Os, a further stage was reached with the storing of data used to run the drawing tables in order to be able to manipulate this data for use in interactive graphic systems (see Dietrich, 1981; Hobbie, 1984). To achieve this, it was necessary to classify the information using one logical system, that is to say, each topographical object was assigned an individual key, and by using a feature coding system, objects could be created consisting of points, lines, and areas. The stereo plotting devices used for this method were still linked to drawing tables, in order to enable the operator to plot a test drawing and thus have an overview and a way of monitoring the captured data.

At the same time as this development, other systems arrived on the market which made it possible to carry out interactive, graphic work directly with a photogrammetric stereo plotter. Such systems developed from CAD technology included Wildmap by WILD and the Stereo Digitizer Interface by INTER~RAPH (Huntsville, USA). It was possible to connect them to both analogue as well as to analytical plotting devices. An automatic drawing table attached to each plotting device was thus no longer required. Their function was replaced by a graphic computer screen. However, the high cost of investment in such equipment and the frequent lack of know-how among users meant that these systems were not widely used. It was the cre- ation of CAD software packages such as AutoCAD (manufactured by Autodesk, Sausalito, USA) or MicroStation (manufactured by INTERGRAPH) at the end of the 80’s, brought about as a result of developments in the personal computer (PC) market, which marked the real breakthrough, and meant that photogrammetric plotting devices could be equipped with, or

modified to run low-cost graphic systems. In the mid 1980s information systems had already been on the market in which photogram-

metry represented an essential component of data capturing. Systems such as PHOCUS by the company ZEISS (Oberkochen, Germany), System 9 by WILD (now COMPUTERVIS~ON, Ztirich), or Intermap Analytic by INTERGRAPH guaranteed the integration of photogrammet- ric data processing into GIS. Overlaying graphic data with aerial photos (superimposition) is a crucial feature of these systems and will be discussed later on, in more detail.

New developments can be seen at the beginning of the 1990s in the field of digital pho- togrammetric workstations, where complex and expensive mechanical, optical, and electronic parts are replaced by a standardized computer workstation (see Ebner, Fritsch, & Heipke, 1991).

A CLASSIFICATION OF INFORMATION SYSTEMS

According to Calkins and Tomlinson (1977) an information system can be defined as follows:

An information system should aid the user’s decision-making ability in the areas of research, planning and management. It operates on several levels ranging from observation and the recording of data, the analysis of this data through to assisting decision-making processes

In order to use a computer-assisted information system in the way defined above, it should contain the following basic components (see also Bill & Fritsch, 1991; Burrough, 1987):

* capturing and classsification of data, l data management,

Photogrammetry as a Component of GIS 225

l data extraction, l manipulation and analysis of data, l data display.

These basic components are fundamental to every hardware and software configuration within spatial-related information systems. A listing of such configurations can be found in Schroth (1989).

Photogrammetry is essentially concerned with the first basic element mentioned, namely the capturing and classification of data, and is, as such, as valuable a method of registering infor- mation as terrestrial surveying or the digitizing and scanning of analogue material. The pure recording of data does not necessarily require an advanced information system. The individual categories of application will therefore be classified below, but the raster data processing and

hybrid systems will not be dealt with here (see Figure 1).

CAD Systems

The simplest level of application in graphic data processing is the use of pure CAD systems to create and manage drawings. Computing attributive information or classification takes place solely within the graphic mode (for example, in the allocation of colour, types of lines, layers etc.). Data management here is basically straight-forward, namely that graphic objects are mainly controlled by the classification of characteristics and interrelated links mentioned above. Examples for such systems in CAD cartography include the products AutoCAD (by

AUTODESK) or MicroStation (by INTERGRAPH).

Dual Database Systems

In contrast to pure CAD systems, dual systems operate by linking alphanumeric data with graphic data. Data is stored separately in two databases, the alphanumeric data being stored in hierarchic, network-like or relational databases. It is possible to perform retrieval functions in the graphic and/or alphanumeric data areas. Examples of such functions are as follows:

l a display of power-lines of type XXX which are older than 10 years and which have malfunctioned more than 5 times; or

l lists of all owners of land parcel on map number yyy.

be classified below. but the raster data processing and hybrid systems will not be dealt with here (see figure 1).

Spatial-Related Information System

p/ link-up -1

or

Combined Database

FIGURE 1. Databases Used to Organise Spatial-Related Information.

A few dual database systems can be mentioned here, such as IGDS/DMRS (by INTER- GRAPH), Mi~roStation (by INTERGRAPH) in connection with a relational database like INGRES (by Relational Technology, Alameda, USA), ARC/INFO (by ESRI, Redland, USA), GRADIS GIS (by STRASSLE GIS, Zurich), or PHOCUS (by ZEISS) with ORACLE (by ORACLE Corp., Redwood Shores, USA).

The establishment of GESs is possible using this design, which also allows the integration of topological relationships in its application.

Co~bi~ed Databases

The most advanced form of spatial-related or GISs currently in use is the combined database. Graphic and alph~umeric data are managed together in either a relational or object- orientated database (see Herring, 1989; Scheck, 1988). Control of topological components in this system has been partiy achieved and includes a topological editor, which means that a twin-level solution as in the dual databases is not required. However, problems still arise today with the response/time ratio, when large amounts of data are involved. These systems are only viable for production purposes if the hardware is high quality and equipped with a fast proces- sor and considerable random-access memory (RAM).

Examples of combined databases include the systems TIGRIS (by INTERG~H), System 9 (by COMPUTERVISION), INFOCAM (by LEICA, Heerbrugg, Switzerland) and Sm~lworld GIS {by SMALLWORLD SYSTEMS, Camb~dge, UK).

The next section deals with the effects of this classification which has evolved within infor- mation systems upon photogrammetric systems and ideas.

FHOTO~RA~~ETRIC SYSTEMS AND IDEAS

Besides the classic division of photo~ammetric stereoplotting devices into analogue and analytical technology, two new stages of development have recently been reached, namely integrated systems and digital photo~ra~e~ic workstations.

A~aiog~e and A~a~~ica~ Systems

1. Even in the age of computer technology, many analogue plotting devices are still in use. Their cost-effectiveness is due to a number of reasons:

(a) High initial investment meant long term depreciation. (b) Robust cons~uction gu~anteed a long lifespan. (c) The use of analogu~-digital-converters and desktop computers accelerated

orientation procedures. (d) The link-up with CAD systems created an adequate working place for the graphic

recording of data. Another consideration regarding cost-effectiveness is that the limited application of

recording purely graphic data means that the ratio of orientation to stereo plotting time is relatively small, so that the advantages of analytical systems are hardly felt.

The use of existing analogue plotting devices linked up to simple CAD systems on a PC basis is today still justifiable in the area of recording data for spatial-related information systems.

2. The development of analytical plotting devices is similar to that of anaiogue. It was only with the link to CAD systems that graphic data processing became a cost-effective method. It goes without saying that the well-documented advantages arising from the universal applications of analytical systems bring decisive benefits.

Photogra~~et~ as a Component of GiS 227

These systems and ideas, relating both to analogue as well as to analytical equipment in the field of graphic data capturing, represent only the first stage towards establishing a GIS. In the next stage, the processed vector information must be converted topologically in order to be able to carry out spatial-reIated analyses. An example here is the concept presented by the company LEICA, which integrates information gained photogra~e~ically with their software product INFOCAM to create one topological database. Another example is the product MGE (Modular GIS Environment) available from INTERG~PH, with which graphic information obtained using Mi~roStation is converted into a topological structure.

Integrated Photugrammetric Systems

The term “integrated systems” denotes photogrammetric plotting devices which are fuIIy linked up to GISs. Topologic~ relations are taken into consideration directly when data is pro- cessed. As far as topology is concerned, a complete integration has, to the author’s knowledge, to date, only been achieved in System 9 and PHOCIJS on a two-dimensional level. A partial integration is available in the system Intermap Analytic (by INTERGRAPH). An actual overview has been given by Makarovic (1992).

Only the future will tell whether the highly complex data processing involved in the fully integrated system will replace the use of the two-level solution -that is to say, processing and following topological conversion. Moreover, there is the immense contradiction between pho- togra~et~ as a 3-dimensional measuring process, and topology limited to 2 dimensions, as used in practice.

digital Photogrammetric ~or~st~tj~~s

The capability of computer technology today regarding the speed of processors and memory size makes it possible for the knowledge gained from the field of raster data and image pro- cessing to be used in the pIanning of digital photo~a~e~ic workstations (see Gri.in, 1989; Leberl, 1991). The linking to GISs is virtually ideal here, as the hardware con~guration is almost identical.

The development of such systems is either at different stages or still in the prototype stage. The systems DSPl (by LEICA), DPW (by HELAVA, Ass. Inc/LEICA), T10 (by MATRA, St. Quentin en Yuelines, France) and Image Station (INTERGRAPH) are worth mentioning here. Breakthrough for these systems hinges very heavily on the costs involved in computer hard- ware and the production of digital image data (see Schroth, 1992).

Digital photogrammetric workstations in connection with image processing and GISs will be at the centre of future development for photogrammetric equipment (see Dowman, 1992; Leberl, 1992).

The scale of developments in data processing and the ensuing effects upon photogrammet~c data processing directly influence working procedures regarding practicaf application, This will be outlined in the following sections.

CHANGE OF WORKING PROCEDURES

The ~ansformation in the nature of photogra~e~ic data rapturing is directly linked to the switch from the analogue map to the database. This change does not mean the production of exactly the same product using different methods, but the production of an entirely new prod- uct. The fact that databases require all data to have the same format (consistency) considerably

228 Ft. Sc~rof~, H-D. Adolf, and J. ~~ng~ofef

reduces dependency upon individual sources. For example, individual operator influence upon graphic layout is closely controlled due to set libraries of symbols or having to adhere to a data structure defined strictly by the user interface. A consistent level of quality and precision draw- ing is also attained, regardless of how the operator is feeling on a certain day, through the use of systems with superimposition, i.e., overlaying graphic information with aerial images.

The broader spectrum of application, e.g., spatial-related analyses of the information gained, demands new and extensive quality controls. Issuing a control plot is in no way sufficient any longer. Special tailor-made check programmes are necessary in order to control consistency, the adherence to requirements (rule base), or the process of interrelating data.

New system developments also create new areas of work. The superimposition method noted above provides a very refined way of updating existing graphic databases (see Arnold & Schroth, 1990), and also quality control of information which has not been gained photogram- metrically, i.e., by digitizing analogue maps.

This change in procedures also has a direct effect upon staff skills. Besides mastering the fundamentals of photogrammetry and the ability to abstract and interpret the information obtained, an operator must also be familiar with handling graphic hardware and software sys- tems. Even user interfaces which have been carefully conceived require a minimum of back- ground information about the structures and patterns of a system in order to be able to make the correct decisions in critical situations. Standard training along these lines is currently not available, which means the user’s employees need cost-intensive and time-consuming in- house training.

EFFECTS UPON PRODUCTION PROCESSES

The changes in working procedures described in the previous paragraph - due essentially to the complexities of planning processes, which are of paramount importance in this day and age, particularly in the area of environmental studies - have a direct effect upon the produc- tion processes involved in obtaining information. The mass of extremely varied information and its internal relations can only be effectively and extensively processed with the aid of data processing technology. For this reason, technical planning of such aspects is the first stage of every project, even for obtaining photogrammetric information.

Definitions must be made within the project planning concerning the objects to be taken into account, as well as how they are to be linked to each other, and how their ch~ate~stics are to be recorded in the design of the database. Graphic format must be determined and the link to, and possible integration with existing information also has to be considered. In order to simpli-

fy the data capturing process, and to full3 what are often very complicated requirements as exactly as possible, special project-based user interfaces should be created during the concep- tion phase. All this means a great amount of preparation to coordinate a project and is generally irrespective of the size of the project.

Preparation work should be carried out in close liason with the users and the clients and often means a considerable amount of explaining and consulting. This is especially true when the data have to be captured in a different GIS than the final system of the client. Even aspects of the translation software have to be taken into account during project planning.

Regarding the overlap between individual production departments, data processing guide- lines are to be adhered to closely. The information obtained from various specialised disci- plines is generally run together in the database management. In the past, the finishing touches at the end of a production process were added manually to the final drawing. Today, in con- trast, a comprehensive integration process is necessary. Geometrical information from pho- togrammetry, thematic information from remote-sensing and a wealth of other information is all entered together into a GIS. This integration process, which takes into consideration depen-

Photogrammetry as a Component of GIS 229

dant factors, clearly limits the flexibility of project management, and means that individual employees need to be thoroughly briefed about a project.

As a result of the technical developments outlined in the sections entitled “Classification of Information Systems” and “Photogrammetric Systems and Ideas,” the productivity of pho- togrammetric stereo plotting has been significantly increased. This is, however, more than off-

set by the additional areas of work noted above. Obviously, the change in the nature of the products must also be taken into account, although a comparison of economic viability is diffi- cult to achieve given the problem of objectively evaluating quality.

CONCLUSION

The rapid developments in the field of data and image processing have caused vast changes in the world of photogrammetry. Not only has equipment undergone changes, but, also, the products to be created have reached a level of complexity which would have been unthinkable in the age of analogue map production. Today, we are just at the beginning of this development.

The production process will be further influenced dramatically with the integration of digital photogrammetric workstations in the existing production environment. There will be two paral- lel production lines with analogue images and analogue/analytical photogrammetric systems and digital images with digital workstations. The near future will bring the integration of the new systems, not only under technical but also under economical aspects.

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