Juan Manuel G. Racca * - Carlos A. Canoba * - Héctor C. Peña *

ABSTRACT

          This paper briefly reviews the use of the techniques of Photointerpretation and Remote Sensing taught in Surveying Education in the Facultad de Ciencias Exactas, Ingeniería y Agrimensura de la Universidad Nacional de Rosario as well as their evolution along three decades. Some considerations relative to syllabus and curricula contents, as well as to the teaching methods are made.

INTRODUCTION

          In accordance with the 1996 Curricula, the subjects that concern us – Photointerpretation and Teledetección (Remote Sensing) – are comprised in the Geographical Information and Cartography Area of the Studies and are linked to the capture, processing, analysis and representation of geospatial information. The Department of Geological Sciences supervises these studies, the emphasis being placed upon the production of thematic information related with the geographical space.

The use of aerial photographs started in the Faculty at the end of the 40s, and was introduced by Dr. Pierina Pasotti. She was born in Rosario and was a graduate in Natural Sciences from the University of Turin. After the Universidad Nacional de Córdoba revalidated her Geology degree, she became a member of the Faculty in 1928. She finished her long and fruitful career as Emeritus Professor while continued working until she died in 1994 at the age of 92. In the fifties, she used Photointerpretation as an auxiliary technique in her research in Tandil and in the Calamuchita valley. As Regular Professor of Geology in Civil Engineering and Surveying, she introduced the reading of air photographs. She then fostered the training of human resources in the techniques of Photointerpretation. She succeeded in sending her young assistants to specialise in ITC in Delft, Holland, and in the University of Sao Paulo, Brazil. When these assistents returned, the unit of Photointerpretation was established in the Institute of Physiography and Geology to support research and post graduate courses. At the same time, Photointerpretation was incorporated to the 1960 Curricula of the Geographical Engineering Course, as an optional subject.

UNIVERSITY TEACHING

After the amendment of the curriculum in 1975, Surveying is recreated and the curriculum of Geographical Engineering is changed. In both of them, Photointerpretation is an annual compulsory subject of the syllabus corresponding to 4th year. Interpretation of Images is added to the 6th year syllabus of Geographical Engineering and is considered the forerunner of the current Teledetección (Remote Sensing).

In 1985, the curricula is amended once again: Geographical Engineering Studies disappear as such and Surveying becomes a 5-year study course; Photointerpretation is an annual subject in 4th year with an abbreviated syllabus similar to the one approved for the preceding curriculum but adding some topics: Satellite Images. Visual Interpretation. Fundamentals of Digital Processing.

In 1996 Surveying Engineer as such is created after one more amendment: Photointerpretation is a subject to be followed during the second semester of the third year. It is structured as a half-term subject and covers: Photointerpretation: introduction. Fundamentals of the electromagnetic spectrum.

(*) Instituto de Fisiografía y Geología 'Dr. Alfredo Castellanos' y Departamento de Ciencias Geológicas 'Dra. Pierina Pasotti'
Facultad de Ciencias Exactas, Ingeniería y Agrimensura, U.N.R. - Av. Pellegrini 250 - (2000) Rosario - República Argentina.

The aerial photograph. Elements of the photographic image and its relationships with the terrain features. The process of photointerpretation. Stones' ideas. Fieldwork. Cartography of interpretation. Remote sensing as a global concept.

          Teledetección (Remote Sensing), a one term subject, is included -as an optional subject - to the curriculum currently in force. It is to be followed during the first semester, in the 5th year, beginning as of the year 2000.

          Photointerpretation, in Surveying Engineering, corresponds to the sixth semester of the course. It gives final competences on the basic knowledge of the techniques for interpreting aerial photographic images to use them and operate appropriately, in order to be used for evaluation of land features, for applications in topo-cartographic surveys, for the study of communication ways location, for cadastral surveys and territorial regulations, for designing the corresponding thematic cartography and for it being used by allied professional fields. In the previous semester, students follow a course on Geomorphology and Edaphology, that prepares them for the proper learning of Photointerpretation. In the same semester, students follow a course of Photogrammetry that contributes the fundamentals of aerial photographs geometry and also focuses on the advantages and drawbacks of aerial photographs when used to prepare basic cartographic documents. This subject also introduces students to stereoplotters, and provides them with the knowledge to make photographic and cartographic documents and, above all, topographic maps with the corresponding contours. Geomorphology, that focuses on the shapes of the earth relief, and Edaphology, which considers the soil to be the supporting element of the vegetable kingdom, both in their character of Earth Sciences, offer basic knowledge to read and interpret images. The role of the former is crucial to relate to the stereoscopic model which is obtained by observing an aerial photographic pair while the role of the latter is to facilitate the comprehension of phenomena with different reflectance which are associated with tones and textures recorded in aerial photographs.

          Classes are scheduled in six periods a week, given in two three-hour class units: one for the theoretical contents and another for preparation and execution of practical applications. In total, 96 periods, time enough to cover the corresponding syllabus and fulfil the intended objectives. A sequence of thematic units is generally respected during the term. The first unit considers Photointerpretation as a technique that allows collecting information that can be used to make maps from the data provided by air photographs and other type of images. In units 2 and 3, the course covers the spectral, geometrical and codification aspects of data sources. Unit 4 covers the characteristics of terrain features and elements of aerial photographs and -particularly- the main relationships that may be established. Unit 5 covers the analysis of the above mentioned relationships and studies them all in detail. Students are taught how to treat the collected information, that is, how to derive or provide meaning to the data according to the intended objective. Unit 6 covers methodologies that, when objectives are clearly laid out, allow proper operational procedures. "Fieldwork" is contained in unit 7: the idea is to provide students with a good understanding of fieldwork significance as part of the method of photointerpretation. Unit 8 refers to an important task for the Surveying Engineer: how to dump the interpretation to the base map, with the "language" appropriate for the objective of the work and for the scale used. In Unit 9, professional applications are covered through examples which include the role of air photographs in the field notebook and in report writing. When carrying out practical applications the goal is to provide an adequate co-ordination with the thematic contents for the task to be as effective as possible.

          Teledetección (Remote Sensing) in Surveying Engineering corresponds to the ninth semester and covers the basic techniques of visual interpretation, of digital processing and of the integration of remote sensed images in geographic information systems to help Surveying Engineers use these techniques appropriately.

          Classes are scheduled in four periods a week, given in two two-hour units one for the theoretical contents and the other for the preparation and execution of practical applications. In total, 74 periods, time enough to cover the corresponding syllabus and fulfil the intended objectives. A sequence of thematic units is generally respected during the term. In the first unit, Remote Sensing is introduced and considered as a technique allowing the elaboration of information that can be used to make maps from the data provided by pictorial or digital images. Units 2 and 3 cover the physical basis of remote sensing, followed by the different platforms and sensors utilized for the observation of earth resources. Unit 4 covers the reading and visual interpretation of images, according to the different levels of perception and in terms of spatial, spectral, radiometric and temporal resolutions together with the scales of analogical products. Unit 5 introduces the fundamentals of images digital treatment along with the restoration processes that are crucial to proper operation. Unit 6 expands digital processing to improve the pre-processed images and get new enhanced scenes with better visual qualities or to synthesize the data contained in those multi-spectral images. Unit 7 deals with digital processes aimed at deriving information from images; these processes include relating, categorisation, discrimination, classification and automatic treatment of multi-spectral patterns and of temporal changes. Unit 8 deals with the processing that cannot be included in the above mentioned classes and that might be useful when preparing the different topics; it focuses on the integration of images and the information elaborated from them in a geographic information system. When carrying out practical applications the goal is to provide an adequate co-ordination with the thematic contents for the task to be as effective as possible. The geographic information system used is IDRISI, in its two releases (DOS and WINDOWS). We benefit from its low price and its adequacy to teaching purposes. However, customised software has been developed and used since 1981 to process different data. The list of customised computer programs are attached to the analytical syllabus bibliography.

          The bibliography, in both subjects, deserves special consideration. The syllabi are complemented by a series of basic texts, by classic and well-known editors and authors. The fact that most books are in English and only a few students can read them is a real drawback. Anyway, there are some texts in Spanish available to students. There are some publications that can be used as reference material, with papers that could be used as examples to those students who would like to study in more detail. For both subjects, the reference material consists of the one above mentioned, as well as other publications and specialised magazines, for example the collection of Photogrammetric Engineering and Remote Sensing and the ITC Journal that can be used both by professors and students. To be in line with current and up-dated information, a subscription to at least two or three of the most important magazines in Photointerpretation and Remote Sensing and to get the proceedings of congresses organised by the Comisión VII of the ISRSP, SELPER and others. Students can always resort to databases and libraries, for example through Internet.

          The teaching process is developed within a "constructivist" pedagogy. The student is the centre of the teaching-learning process and the teacher facilitates that process. Therefore, bibliography, the use of technological resources and tests vary depending on students, who have different cognitive and procedural levels year after year. Class work allows for contact with new tools which aim at achieving a certain professional competence. As the subjects are technological, practical applications are carried out with individual reports. Thus, students can identify with the images that are the basic data source to elaborate cartographic information. So, Earth Sciences are integrated here, an essential tool for the professional performance of a Surveyor. Subjects provide elements for “know-making”, necessary to facilitate the “know-know” and which lead to "learn how to learn" (according to Aebli), a stage previous to developing the "autonomous thinking" that every university graduate should have. We are very much interested in the use of air photographs and other type of images of plain areas. The geomorphologic features of the pampa, the amplitude and frequency of its relief and its taxonomic aspects make this area singular from a geographical standpoint. One of the topics to study is the most effective range of photo scales that may enable us to study this relief, making the most out of the whole stereoscopic view. It is worth insisting on the fact that staff do research and provide services for third parties. Technical and scientific papers are presented in speciality congresses and seminars, and are timely published. The Faculty has its own series of publications. Staff have presented the original results of their work together with those topics that are worth publishing, and will continue to, in future. Staff pedagogic and technical training is considered part of a continuous process. Today, the use of software for digital processing of different types of images and the relationship with geographic information systems is highly esteemed; there is still a lot of work and possibilities that available software may offer. Anyway, the use of aerial photographs still cover a wide range of needs and provides proven information, especially at medium and large scales which are the most frequently required in the professional tasks. Therefore, the use of Photointerpretation operative methods should be reinforced.

          Besides, in Geomorphology, Edaphology and Geology and Geotechniques -subjects taught through Geologic Sciences Department for Surveying and Civil Engeneering courses- the aim is to point out the significance of practical applications where remote sensing techniques are included. The interpretation of aerial photographs is a key element to see the landscape and collect relevant data.

          The current curricula of Photointerpretation and Teledetección (Remote Sensing) are attached with details of objectives, contents, practical applications and bibliography. The bibliography includes all the publications done by the professors of these subjects.

CONCLUSIONS

          A thirty-year experience in teaching Photointerpretation and Remote Sensing (previously called Image Interpretation) allows us to state that this area provides for an extremely important tool to Surveyors: it offers a holistic standpoint that from data gathering moves to data processing to derive relevant information that leads to the final mapping stage.

          The current orientation, in research as well as teaching, is linked to the digital treatment of images and its integration, together with data coming from other sources, into geographic information systems. However, it is never ignored that the interpretation of aerial photographs and satellite images should be supported by a solid and specialised training of the professional who performs it, as well as by the knowledge of Earth Sciences, especially Geomorphology. Moreover, though the potential that digital processing can offer is highly esteemed, the traditional method of photointerpretation and aerial photographs still has an important role, due to the gathering of information that the stereoscopic model, spatial resolution and scales that these images provide to detailed and semi detailed research – the most frequent in the Surveying field – by meeting the requirements of most demands of cadastral, territorial ordinance and the confection of cartography in the different phases of engineering work.

          An integrative example, is the massive use of aerial photographs and other types of images in research work done and in progress, to study all the hydrographic basins of the south of the Santa Fe province.

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