Re.1.E-(1uIp& ahlam of cxms~wfor p d u ~ i n gmapping p h a t ~ i l . p %df
I N G . P O R F I R IG
O A R C ~DAE L E ~ N *
Comisidn de Estudios del Territorio Nacional
Mtxico 8 , D. F., Mtxico
Mexican Thematic M a p Products
The data collected will provide a combination of scientific,
sociological, political and economic benefits which will
greatly exceed the cost of the mapping program.
(Abstract on page 1208)
M
started to produce thematic
maps using photo interpretation and
photogrammetric techniques. Natural and
cultural phenomena are recorded on aerial
photographs. After these data are collected,
analyzed, interpreted and verified, the pertinent information is plotted on appropriate
topographic maps (compiled photogrammetrically) which then become thematic maps.
These special-purpose cartographic products,
together with additional written information,
are a good expression of the natural resources
inventory.
I n Mexico these methods have been applied
mainly to topographic, geological and forestry
mapping. The experience shows clearly the
advantages of the methods in terms of cost
and speed in contrast to the conventional
ground methods. However i t was necessary
EXICO HAS
* Presented at the Annual Convention of the
American Society of Photogrammetry, Washington, D. C., March 1971.
to integrate several techniques in order to
obtain a total system approach to acquire
intensive, interrelated information on a large
natural resources inventory program.
The pioneers in this field demonstrated that
any sound and well-conceived plan of economic and social development requires an
adequate knowledge of the land and natural
resources available. They showed how photographic interpretation and photogrammetric
techniques supply the necessary basis for
planning and initiating projects of technical
and economic value for the development of
the nation.
I t was not until October 1, 1968, when the
Commission of Studies of the National Territory (CETENAL)
was created as an agency of
the Presidence Ministry. The main objectives
of CETENAL are to prepare the topographic
quadrangles and to map the resources of the
country a t the scale of 1:50,000. With the
information produced by CETENAL,
the government will be able to sustain more accurate
and reliable plans in order to accelerate the
economic and social development of Mexico.
PHOTOGRAMMETRIC ENGINEERING, 1972
As graphic presentation is particularly
suited to visual inspection, the faster form of
data transfer available to humans, the thematic map constitutes one of the principal end
products of the natural resources inventory.
They are one of the most useful mediums of
communication between the resource technicians and the map users: engineers, planners,
economists, agronomists, etc.
Photographic interpretation methods are
used for detailed studies of the terrain in
order to obtain four different thematic maps.
Each one shows basic information related to
geology, land use, soils and potential land use.
Photogrammetric techniques are used to produce the topographic map which, in addition
to its intrinsic value $er se, also provides an
adequate reference frame for an accurate location of natural resources, thereby assuring the
precise mapping of the forms and positions of
significant features.
CETENALhas a tremendous task ahead.
Mexico has an area of 1,972,571 square km
(760,337 square miles). I t is the third largest
country in Latin America. T o accomplish the
task i t will be necessary to produce almost
11,000 original map sheets, presented in a
series of five maps (the topographic map and
the four thematic maps) a t 1:50,000 scale.
The long-range national plan will be completed in a 10-year period in its initial stage.
As many of the phenomena affecting resources are time dependant, a repeated coverage is needed in such a way that another
stage of the long-term program must be to
create a current map series, to update existing information periodically to preserve the
value and usefulness of the maps.
During the first year of CETENAL the personnel had to be trained. A t the same time i t
was necessary to make the proper selection
of the equipment (Figure 1) and to prepare
the offices, hangar, laboratories and all the
facilities needed. The collection and compilation of the available data was another important requirement achieved.
The topographic maps are obtained by
photogrammetric methods from vertical aerial photographs a t the 1:50,000 scale. A-7
Autographs (Figure 2) are used for the aerotriangulation and the Stereosimplex 11-C
plotters (Figure 3) for compilation. Level-line
and traverse surveys are made for establishing
proper ground control. The country was divided into 85 working areas and, in order to
reduce the cost of the ground control, their
FIG.2. Wild Autograph A7 for aerial triangulation;
to the right is a desk co~puter.
east and west limits were usually highways,
dirt roads or railroads.
Some of the control points are marked on
the ground by bench marks which are shown
on the maps and the results of control surveys
are published in numerical catalogs. Field
classification is done in order to classify roads,
transmission lines, watercourses, etc., and to
add geographic names, as well as other pe tinent information. The computations i
volved in the ground control surveys, the
aerotriangulation and the Universal Transverse Mercator (UTM)grid coordinates, are
performed by electronic computer.
.
The final topographic maps, presented in
four colors (Figure 4), are quadrangles of
20 X 15 minutes of latitude and longitude, respectively. Each quadrangle covers an area
of approximately, 1,000 square km. The publication scale is 1:50,000 with a 10-meter contour interval.
f-
The Photointerpretation Departament of
has established a general working
method suitable to the investigation of natural resources and to the production of the
thematic maps. The method is based mainly
CETENAL
FIG.3. The Photogrammetry Department of CETENAL has 20 units of the Stereosimplex 11-C.
MEXICAN THEMATIC MAP PKODUCTS
FIG.4. A portion of the Pinos, Mexico, topographic map.
on photographic interpretation techniques
(Figure 5) which have been proved invaluable
tools for a better understanding a n d knowledge of t h e natural a n d cultural resources, as
well a s on t h e fact t h a t t h e best way of recording a n d analyzing natural resources is
through t h e use of thematic maps.
T h e steps established b y t h e Comn~ission
in the resources investigation are t h e following:
Compilation of existing information concerning the area studied.
Reconnaissance trip to the area.
Photointerpretation of color aerial photos a t
the scale of 1:25,000, selecting the check points
and the routes to follow.
Field investigation and written standard report for each check point.
Correction of the photointerpretation based on
field checking.
Compilation of the resource map using the
topographic map as a base.
Quality control verification of the map in the
held.
Geological maps (Figure 6 ) provide essential information t o discover a n d evaluate nat-
FIG.5. A view of part of the Potential Land Use
office of the Photointerpretation Department.
ural resources and their potential yield. N o
thorough understanding of t h e natural phenomena can be achieved without the geological investigation. A t the same time photographic interpretation has proved t o be a
great asset in this field. T h e results of these
investigations are displayed in maps.
T h e geological maps produced b y CETENAL
show t h e distribution, structural position, a n d
contacts of t h e various types of rocks, a s well
a s soil units. T h e y contain geological features
such as: fractures and faults, folded structures, volcanic cones, lava flows, dikes, veins,
sinkholes, etc. T h e producing mines o r prospect mines, salt domes, oil fields, abandoned
o r operational quarries a n d borrow pits, whatever constitute valuable economical information, are shown o n t h e map. T h e control points
of t h e field checking are also shown on t h e
map.
T h e geological investigation performed is
of a practical nature; i t is directed mainly
toward t h e possible economic utilization of
rocks, soils, water and minerals. Additional
information is obtained from t h e field survey.
A written report of each control point is prepared b y the'geologists. T h e rePoit depicts information about:
Rocks. Megascopic classification, stratigraphy,
structures, metamorphism, permeability, physical characteristics of rocks as construction
materials, etc.
Soils. Classification regarding origin, depth,
texture, resistance to compression and presence of other components.
Minerals. Existence of metalic and non-metalic
minerals, form and economic possibilities of
the ore deposits, radiometric measurements.
Water. Superficial sources and possibilities of
springs and their importance.
Construction materials.
FIG.6. A portion of the geological map Tanque de Dolores.
a
A basic element of t h e resources of a n y area
is t h e use t o which t h e land is dedicated, a s
well a s t h e types of t h e vegetative cover. T h i s
information is displayed o n t h e land use m a p
(Figure 7). T h e m a p also shows b y a code, t h e
available public services i n rural a n d u r b a n
areas, such a s water supply, sewage, telephone, school, hospital, etc., a s well a s population. T h e related investigation i n this field
is conducted b y agronomists a n d geographers
with special training i n photointerpretation
techniques.
T h e report of t h e control points studied o n
t h e ground provides further information,
among others, related to:
Agriculture Land. Irrigated by pumped system or gravity fed. Non-irrigated land (permanent or nomad). Crop type (annual, permanent or semi-permanent). Specific crops
important in the area. Estimated annual
yields. Market prices. Farm implement used,
etc.
Grassland. Open and scrub grassland. Improved pasture. Induced grassland. Cover
density and important species. Type of livestock using the grassland or pasture.
Forest land. Cover type characteristics: species composition, stand height, number of
commercial and non-commercial trees per
hectare, etc.
a Characteristics and composition of all other
vegetative cover types.
Eroded areas classified according to the cause
and degree of erosion.
Characteristics of archeological, industrial,
rural settlements and urban areas.
Water ponds. Classification, fisheries.
a Areas lacking vegetation. Rock outcrops, bare
soil.
T h e soil is considered t h e most valuable resource i n this program. H e r e t h e concept of
soil is defined as: " t h a t p a r t of a natural a r e a
of land occupying a portion of t h e earth's surface which supports plants, a n d has properties resulting from t h e integrated effect of
FIG.7. A portion of the land-use map Espiritu Santo.
MEXICAN THEMATIC MAP PRODUCTS
FIG.8. A portion of the soils map Ojo Caliente.
climate and living matter acting upon parent
material, as conditioned by relief over periods
of time". T h e soils map (Figure 8) is the
product of photointerpretation, field investigations and laboratory analysis, which
result in the correct classification of soil units.
T h e classification used is the International
Soils Classification PAO/UNESCO, proposed to
complete the soil map of the world.
Each soil unit on the map has a distinctive
symbol expressed as a fraction containing
four parameters:
Classification Unit - Phase
Textural class - Topographic class
The numerator express the corresponding
symbol of the PAO/UNESCO classification with
its soil phase, which is a variation within the
soil type according certain characteristics. I n
the denominator, the textural class refers to
the relative proportions of clay, silt and sand
in the soil. T h e topographic class depends on
the slope of the terrain.
I n the field, the soil specialist takes notes on
soil color, depth of soil, thickness of horizon,
texture and structure of the soil. H e reports
information about climate, physiography,
parent material, vegetation cover, crop types,
human influence, limiting factors, etc. He also
samples the soils in pits, road cuts or ditch
banks and describes the pertinent characteristics of the soil profile. Soil samples are collected for laboratory analysis which provide
additional data mainly for fertility studies
and classification purposes. The data available from the topographic map, land use and
geology maps comprise the basic foundation
for the soil map.
THEPOTENTIAL
LAND-USEMAP
The multidisciplinary d a t a collected and
integrated serve as a basis for the preparation
and production of the potential land-use map
(Figure 9). T h e information from the other
disciplines precludes and sustains the potential use of the land. In order to develop
properly the inventoried resources, i t is neces-
FIG.9. A portion of the potential land-use map Puerto Madero.
sary to plan or propose transportation sys- niques, and especially those of remote sensing,
tems and other engineered structures, such as
dams, in locations which serve best all the
resources in a particular area. The personnel
working in the production of the potential
land use map are agronomists, civil engineers
and economists.
The work is divided in two stages:
* ~ , capability
~ ~ classification,
d
showingalso the
limiting factors, as well as erosion control,
where soil protection is needed.
* Proposition of infrastructure and ineans to
provide services to rural areas.
The potential use map shows by a Roman
numeral (I to VIII) the land capability classification according with the Manual of Soil
Conservation of the U. S. Agriculture Department. The limiting factors of the soils appears under the classification symbol mentioned earlier. These factors are: soil, climate,
topography, erosion and floods; each one is
will soon come to aid in searching for our natural resources. This multidisciplinary program where different disciplines are used
together, has the advantage of complementing one another in their results, hence its
broad applicability.
The data collected by the program will provide a combination of scientific, sociological,
political and economic benefits. These benefits will greatly exceed the cost of the program.
The amount of data gathered will be considerable, therefore i t is necessary to make
them available in a digest form for general
planning purposes. One of these forms is a
map. But a map is merely a means toward an
end. Afterwards, the evaluation and further
utilization of resource data is required. These
studies can serve to decide on an appropriate
strategy of development, and translate this
Mexico needs to plan its social and economic development; these
ABSTRACT:
plans require basic information about natural resources. Photographic interpretation methods provide adequate means to obtain such information. T h e results of
the investigation must be available to the users in a proper w a y . Thematic m a p s
constitute a n effective and rapid form of data communication.
T h e Commission of Studies of the National Territory was created by the M e x i can government in 1968. I t s m a i n task is to prepare topographic m a p s , obtained
photogrammetrically, and to m a p the resources of the entire country at the scale
of 1 :50,000. T h i s Commission produces four thematic m a p s related to geology,
land use, soils and potential land use.
represented by a letter. The proposed services
to rural areas are shown on the map by a codenumber which indicates the services needed.
The propositions of route locations, site dams,
transmission lines, water supply lines, etc.,
are well founded on the information gathered
from the topographic, geologic, land use and
soils maps.
The written report gives information about:
f Soils. Depth, drainage, stoniness.
strategy into programs of action and investments. An enlightened approach to project
evaluation can help accomplish these objectives.
The information obtained by this program
can be used as a foundation to attain a correct
and complete plan of Mexico's social, economical and technical development in order
to assure a better standard of living for the
people.
7 Topography. Regular or irregular slopes.
f
Water. Lack or availability.
f
Frequency of jloods.
7 Climate. Cyclones, frosts, snowfall, rainfall.
7 Erosion. Origin, type, grade, control.
The study of resources made by CETENAL
is of general purpose only; therefore, i t is still
possible to extract information from the photographs for more detailed studies. The utilization of new tools offered by modern tech-
M y thanks are due to Engineers Juan B.
Puig and HCctor Alonso, Director of the Commission of Studies of the National Territory
and Head of its Photointerpretation Department, respectively, for their papers presented
a t the Symposium of the International Society of Photogrammetry held in Dresden, German Democratic Republic, in September
1970. They furnished hasic information for
this paper.