Previous Page Table of Contents Next Page


Review of the discussions


Techniques and cost
Contents and utilization
Training


The discussions can be grouped into three main topics:

1. Technique and cost
2. Contents and utilization
3. Training

Techniques and cost

A. DIAOURE:

Two remarks about one of the slides presented by Mr. C. Cazabat:

1) It is dangerous to use ERTS photos that present dry river beds as though they were still filled with water. Therefore field work is very necessary.

2) The quality of the negatives is a result of atmospheric conditions. Yet acceptable photos can be obtained for the Sahel because the satellite passes over the same point every 18 days.

To comment from another point of view on the statement of Mr. Cazabat that everyone is capable of making maps, would like to emphasize that it is difficult for non-specialists to make maps.

C. CAZABAT:

In answer to the three points raised by Dr. Diaouré:

1) The negative presented was made with an electronic density process. There was no interpretation. It is, of course, necessary to do verifications in the field before making a map.

2) You have only a few chances for good film shooting in the course of a year for the whole Sahel. Therefore it is difficult to follow an evolutionary process by a satellite photo.

3) Making maps demands a little training, but everyone is capable of doing it.

The recordings are made with a picture resolution on the order of 50 metres x 60 metres and the reflection recorded (that is, the energy level) is a result of the surface. That poses a problem for the interpretation of indirect criteria: geology, geomorphology, hydrology.

Photo-interpretation calls for a long, proven experiment.

N. MCLEOD:

The photograph presented by Mr. Cazabat and discussed by Dr. Diaouré was taken by Apollo 9 in the spring of 1969. A photo taken by the Nimbus one month later shows very well that there is no water in the lake in question.

A. BLAIR RAINS:

The use of film with one emulsion coating, makes it difficult for the non-professional to distinguish with precision the shades in the different colors of a photograph; at that point it is necessary to call in professional photo-interpreters.

C. CAZABAT:

In fact it is difficult to interpret a panchromatic film, because the same gray can represent the vegetation or different types of soil. ERTS permits working with different colors of the spectrum and with different media. The multi-spectral recordings bring new possibilities to interpretation if you know how to read the different media. Photo-interpretation is within everyone's reach. It is necessary to be a botanist first of all and then to take a course in photo-interpretation; the opposite would be difficult.

G. DE WISPELAERE:

The problem is not a problem of emulsion but a filming problem. The use of infra-red color makes sense only if the vegetation has reached its maximum growth level and is still green. Emphasis should be laid on the time of filming. It corresponds, in our opinion, to the time right after the rains. Yet it's unfortunate that many filmings do not take this into account.

A. BLAIR RAINS:

One of the drawbacks to the use of infra-red color is the prohibitive cost.

S. KANOUTE:

Automatic recordings present more advantages than recordings made with the naked eye.

With an automatic recording the interpretation is much more precise, without excluding control on the ground.

K. VOLGER:

False coloring can be developed according to a "negative" process. This is what the IGN is working on, and it allows for good printing. Yet the positive-positive process can be carried out in numerous countries and the price is not much higher.

It seems possible, even during the dry season, to use false coloring.

The shadows, sizes, and shapes of objects must be used for the interpretation of photos. This will probably never be automated, or at least not in the next 50 or 100 years. The spectra given by a system with more than three channels, like the multi-layer films, are also valuable; several examples have shown it. Therefore, it is necessary to place more attention on the multispectral systems. Nevertheless, the system of false coloring film is at present operationally good and valuable, especially when a certain penetration power is needed for haze, as is the case during high altitude shooting.

N. MCLEOD:

Concerning the spectral sounding apparatus, the information we are researching is in fact the variability of reflection. When the vegetation changes, we record the changes through the variations of the spectrum.

A. BLAIR RAINS:

The use of spectra has led people to consider that characteristics of the terrain were absolute, while they are in fact essentially variable and depend on atmospheric conditions, light intensity, the growth level, in the case of plants. and many other factors.

B. PEYRE DE FABREGUES:

We have tried to find the correlations that exist between the development of the grassland and its representation on negatives made, with this goal in mind, in several coatings, namely panchromatic and false color, and at different scales. The best results are obtained from a scale of 1/10,000.

The comparison was done over three rainy seasons and the test used was the densimetric analysis of the photographic image. We were able to find a not always dependable correlation between the representation of the development of the grassland and the corresponding photographic image.

G. BOUDET:

It is necessary to forecast representative zones in the world. This would allow us on the one hand to fix the satellite negatives, and on the other hand to obtain airplane negatives on these zones and especially to test these studies by representative samples and observations on the ground.

G. DE WISPELAERE:

Are the photographic mosaics stereoscopic? Is it possible to foresee, on a vaster area than the one presented, a combination of several cuttings of the type of the mosaics presented, that is, from non-high-angle photographs at 1/50,000?

A. BLAIR RAINS:

The scale of 1/50,000 is not really appropriate for very vast and uniform zones. In the Sudan a very interesting study at 1/250,000 has been carried out on the basis of two ERTS passings by the Directorate of Overseas Survey U.K. If a wide-angle camera is used for the Sahelian zone and if flight time can be picked, it is then possible, by flying at an altitude of 40 to 50,000 feet (13,000 to 16,000 metres) to take satisfactory photos and to work out small-scale mosaics.

C. CAZABAT:

The studies of Mr. A. Blair Rains are very interesting in the fact that they are based on a physiognomic description. Whatever the scale of the map, it is necessary to bring together as many physiognomic aspects as possible, that is, of photographic type. That doesn't hinder color overloading. Therefore it is necessary to change all the mapping that is based on projection and "flat surface".

M. INUWA:

The information obtained by aerial photography or otherwise, even if it is out of date, is necessary for the researchers and the men in the field. The problems of updating ought not to discourage those who are gathering the information.

A. BLAIR RAINS:

Map updating is essential but difficult to carry out. Our experience has shown us that the validity of a map is about 5 years, and that a great number of copies are not used.

J. VALENZA:

The problem lies in the age of the aerial covering that is used. The maps are actually based on the occupation of the soil.

G. LAMARQUE:

The problem of updating maps is important and profitable. It permits on the one hand habituating the use of mapping and on the other hand, training cartographers in the field.

M. GWYNNE:

Concerning the ecological survey program, the information can easily be updated on the sub-units that are mapped for the different types of vegetation. The areas are observed through repeated flights, and the information is gathered and continually updated. In addition, the construction of new maps will be made possible by the observation of the relationship between the vegetation and its use by the fauna or the nomads over several years, as well as by the observation of rainfall variations and the availability of surface water at certain times.

Contents and utilization

N.G. TRAORE:

Interpretation only has value to a large extent where it is confronted with the reality in the field. It would be inconceivable to distribute a document originating from interpretation without having controlled it. That's the basis of mapping.

G. DE WISPELAERE:

Photo-interpretation is only a way of expressing field observations. It seems unnatural to foresee photo-interpretation without standardization on the ground. Mapping investigation on the ground, associated with agrostological definition of vegetal groups, serves to standardize the different photographs gathered. It is only then that you can proceed to a systematic interpretation.

A. DIALLO:

In aerial photography, some threads appearing to be identical represent in fact, when they are joined with the equivalent in the field, vegetal groups which can be different. When an extensive zone has to be mapped, it is necessary to infer a problem of validity for the map obtained in this manner.

G. BOUDET:

If enough importance is given to the cartographic expression of results of research on the ground, that permits minimizing the error when establishing results from aerial photos.

D. PRATT:

The danger comes from the fact that the cartographer has a tendency to want to include too much information. In so doing the maps become very difficult to read; the value of the maps is reduced as a result for those whose knowledge of mapping techniques is limited. You could provide a maximum of information by using the following technique, which consists of having an ecological map of an area and super-imposable maps having complementary characteristics. If development is desired, a map will have to synthesize all information concerning the characteristics of the biological and socioeconomic environment; for example, the problem of water and the movement of livestock between the dry season and rainy season pasturelands will have to appear. Only then, the valuable and necessary data will be presented together to create development units.

C. HEMMING:

There are two opposing needs; the need to present a maximum amount of information and that of keeping the maps as simple as possible. A person working in the field will have difficulty reading detailed maps, particularly if the vegetation is indicated by the Latin names. To simplify map reading, it should be possible to present a thematic map with an illustrated key which would give explanations and detail concerning the information given on the map. In practice this should do for relatively small areas, but it could become bothersome for mapping of large areas.

G. BOUDET:

Maps are often secondary and are only pictures of reports of activities carried out in the field. Mr. Hemming's suggestion of having the few descriptive summary of 7-8 pages, and attaching them to the map, seems very worthwhile to me.

P. SIMS:

If our objective is to manage pasturelands in order to increase cattle production, too much importance has been given to small- scale maps which are much more suitable for decision-making at the government level than for use by men in the field. Aerial photography on a scale, for example, of 1/15,000 would be more useful to the man in the field and could be used for pastureland management, for water distribution, and for improving pastureland conditions. Mapping at this scale necessitates a great knowledge of photo-interpretation on the part of those who make the decisions.

C. CAZABAT:

The problem is the actualization of the maps. We have old documents on all of Africa (between 15, 20, and 25 years old). From these documents, topographical maps have been constructed from outdated material. If we are serious, it is necessary to start over at zero, that is, to do a complete re-investigation of what exists. This investigation will be of a photographic nature and will permit having up-to-date physiognomic bases. It will then be sufficient to bring the photographic bases up-to-date in the scale 1/100,000 and 1/200,000 for the following plans:

1) Hydrography. It will be necessary to use documents and knowledge that we have on the different wells and their depth as well as on the perpetuity of the different wadis.

2) Network of routes (paths, trails). It is necessary to put this on the map.

3) It is also necessary to locate the different villages and name them.

None of the up-to-date maps gives this information. But this is the basis of the work. Once the mosaics of this type are completed, with concise information brought out, we can begin different projects. This physiognomic map and different basic projects will permit everyone to find what he is researching. That will be valuable for the agrostologist, forester and soil scientist. It is necessary to begin there. In the end these documents will be worked on by everyone, and they will also be the basis for studies on evolution. While these documents are physiognomic and photo-oriented, everyone will be able to go into the field to see what is going on and what interests him.

K. VOLGER:

Concerning the updating of the computer-made maps, it suffices to take from the computer the card that corresponds, for example, to one square kilometre, and to write on it the new result obtained in the field. Computer mapping is considered less expensive than the work done by a cartographer. In addition, it suffices to print larger maps by computer and to reduce them by a simple technique. In this way a better interpretation of the terrain is given.

N.G. TRAORE:

For the wide diffusion of photo-interpretation the price of conventional support must be considered. Should one recommend panchromatic, infra-red, infrared color, or basic color film?

P. LEROUX:

Concerning the costs, it must be pointed out that the cost of the emulsion system is negligible in relationship to the cost of the plane. Furthermore, the photo-interpreter works faster with infra-red color photographs, since they are more sensitive. He moves even faster because he uses smaller scales, that is, he has fewer photographs to work with. Nevertheless, the infrared color film is always duplicated for safety with a panchromatic emulsion film.

N. DAWSON:

On a scale of 1/100,000, the details are visible but in Australia we also use color maps of 1/500,000, which are very appropriate for work in the field. We therefore furnish our professionals with copies of evaluation in the field of 1/50,000. The mapping of 1/15,000 described by Dr. Sims would give much more information for the planning of agricultural work in Australia. Scales of 1/50,000 to 1/18,000 are better suited.

P. GRANIER:

The techniques concerning aridity, vegetation, and the profile of the terrain lend themselves perfectly to an empirical study. However, in the field and particularly in the dry zone it is necessary to emphasize the water problem, which obligates the users to have, in addition to the maps, an accompanying document on hydrography. It should be necessary to mention on the maps, for the permanent bodies of water, the depth of the wells, because on this depends the time that the livestock breeder is going to spend drawing water, and therefore the number of animals to water; and for the temporary bodies of water, the date of drying up, since this indicates the time when it is necessary to distinguish the rainy season grazing from that of the dry season.

A. GASTON:

If you take into account Mr. Granier's comment, the present maps are valuable. A supplementary the development option that is needed, an d showing alterations in relation to it. As for the dates of the drying-up of ponds, they are difficult to specify an agrostological document.

D. GATES:

It is necessary to have ecological maps of a pure basis. They should serve as unit reference maps, and should allow for having overlay pages that would help in decision-making. It's possible that we complicate the problem of scale too much. The scale and map legend depend essentially on the use you wish to make of them. Maps are often used for a purpose other than that for which they were designed, and that's where the problem lies.

D. PRATT:

A small scale is valuable for mapping of large areas not yet mapped in terms of vegetation, livestock and population, in order that we may define potential development units. These types of maps are incomplete when factors such as the social aspect or water distribution, essential to integrated planning, are not incorporated. The procedures described by Sims are suitable for development maps when development units and management guidelines are well defined.

A. BLAIR RAINS:

Unfortunately, it is necessary to observe that a country that will remain unnamed here had very elaborate maps made about twenty years ago. These have just been found in their original package devoured by termites.

P. NDERITO:

The point here is not to criticize the reasons that have led to poor utilization of maps. It is correct to emphasize in this seminar, which brings together on the one hand representatives of ILCA and various international organizations, and on the other hand eminent specialists, that Africa has a better awareness of her development problems.

M. INUWA:

Actually the storage techniques assure better and more rapid use of available documents.

A. DIALLO:

The fundamental problem is that the professionals do not use the maps in the field because they are very complicated. The maps should be simpler, more expressive, therefore easier to read. The vegetation in our Sahelian and Sudanian regions is not as well known as that of other countries. The agrostologist doesn't have any basic documents, and his work is not made easier. Could Mr. Naegele talk about his experiment?

A. NAEGELE:

I have never in 15 years met any men in the field or livestock breeders using the pastureland maps. These maps are too complicated. In the countries visited there are no skilled personnel to use these Simpler maps in black and white with different markings to translate the different types of areas are needed.

P. NDERITO:

Actually the maps are not always easy to read and understand for the men in the field. It is necessary to find solutions to that.

G. LAMARQUE:

In answer to Dr. Diallo, the solution should be the editing of two maps: a "Bible", which would serve as a reference and a data bank and would permit following the change in time; and a simpler map for the professionals in the field. The colors, it should be emphasized, facilitate reading the maps.

P. GRANIER:

It would be necessary from a basis of planimetric maps to add suitable data in terms of different characteristics of the land or of the users.

J.C. BILLE:

A distinction between the researchers and the men in the field is made; but some are both. This might explain why in spite of the usefulness of the maps on a scale of 1/200,000, it is sometimes necessary to have field experimentation, where the evolution can be followed on the scale of the square metre.

It is important to adapt its direction to day-to-day observations, and to take notes, so that everything is explained on one map. It's the synthesis that will give the results.

L. AYUKO:

To plan small units, our technicians use aerial photos and a stereoscope. Is it true that a person using this method.

P. SIMS:

Those who are very familiar with the region under study can go into the field with an aerial photograph, interpret directly what they see, and note the principal characteristics that will permit making decisions. The stereoscope can be used to describe the relief, but this isn't necessary. The administrative decision can be made in the field with an ordinary aerial photograph.

C. HEMMING:

Every one working in the field should have as easy access as possible to aerial photographs, since the maps take a long time to make; for certain work, aerial photographs are handy. Every country should edit its own photographs, and the problem of production rights should be resolved.

B. DESCOINGS:

It would be interesting if the work carried out by the pastoralists in the field were also used by the phytogeographers. For the data gathered by the pastoralists to be used by the phyto-geographers, two small modifications would be sufficient:

1) The collection of some supplementary data concerning the arrangement of the vegetation. In certain cases these data are surveyed, but not always completely, or in a usable form.

2) The problem of standardization of terms and terminology used. With a little effort the terms on the maps could be better standardized. The maps would be easier to read and generally contain more information.

The use of these data by phyto-geographers would have the following interest for the pastoralists: a knowledge of the vegetation on a small or medium scale would permit knowing the actual condition of this vegetation and its development potentialities, thus its dynamics.

Yet what interests the pastoralist in the medium or long-term is knowing what will become of the actual vegetation after several years.

A. MAIGA:

There exists, even between cartographers, a lack of communication and exchanging of information. If the specialists themselves can't deal with these problems, what will happen to us who, on the outside, have to work with the maps for developing the pastureland or the nutrition of the livestock?

G. LAMARQUE:

It may be necessary to draw from a larger number of copies of the maps. The additional cost is small, and this would permit their use by a greater number of people.

S. RISOPOULOS:

As Mr. Lamarque notes, a greater diffusion of evaluation studies would be necessary in Afrique.

Training

N.G. TRAORE:

Concerning the popularization of photo-interpretation, it would be interesting in specialized sections of the university for photographs to be studied and then for a transposition to be made in the field.

N. MCLEOD:

Concerning education, practical training in the field is better than an outline course. It would be advantageous to have a foreigner and a national team up to work, if you want the greatest transfer of information to take place.

P. NDERITO:

Nationals ought to be implicated more in mapping projects. There is a great difference between the average level of the men in the field and the advanced level of the cartographers present at this seminar. A more advanced qualification is necessary so that the average man in the field is capable of using the data represented on the maps. Every existing map will have to be updated, and as far as possible the new maps should be made without taking boundaries into account. In addition, it's possible to indicate the importance of livestock on the maps in order to be able to plan for their movements.

A. BLAIR RAINS:

The Directorate of Overseas Survey, U.K., certain of whose maps you have been able to see, has a specialization course in cartography for the non-British, in addition to the usual training courses.


Previous Page Top of Page Next Page