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A SHADED RELIEF MAP OF MEXICO
José Luis Ornelas de Anda
Dirección General de Geografía, - Instituto Nacional de Estadística,
Geografía e Informática DGG-INEGI
Mexico
Commission IV, Working group 4
KEYWORDS: DEM/DTM, Shaded-relief, Landform mapping, Physiography
ABSTRACT:
Digital shaded relief images offer the possibility to depict the landforms in a detailed and accurate form. In this work, a
Digital Elevation Model (DEM) , three digital images and four paper maps were made. A single DEM, covering all the
continental territory of Mexico was derived from 255 individual one by one degree DEMs. From this model a shaded
relief image was produced, and combining this image again with the DEM, two other images were obtained, one for
stereoscopic viewing with anaglyphs, and other with shaded hypsographic colors. With these images three maps, one
for each image were prepared in scale 1:4,000,000, and one (stereoscopic) also in scale 1:14,000,000. The use of
shaded relief images in physiographic and geological studies, and also in other fields like ecology and education as
well as a component in the preparation of other maps is discussed. Prospects for other derived products from the
DEM, and shaded relief images preparation with more resolution are mentioned.
BACKGROUND
Digital Elevation Models in Mexico.
Derived from the topographic map series in scale
1:250,000, there are 255 DEMs that cover Mexico. Each
model covers an area of one degree of latitude by one
degree of longitude, with elevation values every 3
seconds of arc. The Dirección General de Geografía,
Instituto Nacional de Estadística, Geografía e Informática
(DGG-INEGI: General Bureau of Geography, National
Institute of Statistics, Geography and Informatics), is in
charge of the distribution of these DEMs to the general
public. They have been used for different purposes,
(communication facilities and highway construction
planning, ecological and environmental studies, etc.).
Now, with the digitization of the 1:50,000 topographic
map series, more detailed DEMs are being produced and
its distribution has just started.
Physiography and relief maps.
The complex physiographic characteristics of the Country
are described in several works, among them: Raisz 1964,
Cuanalo de la Cerda et. al, 1989. E . Raisz, based on
aerial photography and extensive field trips produced a
hand drawn map “Landforms of Mexico”, portraying the
relief of the country with an unequaled detail. The map
includes a text in which Raisz proposed a physiographic
division in 11 provinces and 38 regions, with a description
of each.
Cuanalo de la Cerda et al., 1989, made a revision of the
physiographic division of Mexico, and proposed a
hierarchical scheme based on terrestrial provinces,
regions and subregions. For their work they used band 7
of Landsat-MSS satellite images in paper prints at scales
from 1:5,000,000 to 1:1,000,000, and applied a modified
version of the method of Brink. The purpose of their work
629
was to offer a base for land use planning, especially for
rainfed agriculture. ^ Their description of each unit
includes information about geology, geomorphology,
climate, soils and vegetation. In the other hand, the
mapping agency, DGG-INEGI, made another
physiographical division for its own Physiographical map
series in scale 1:1,000,000. In this case the maps were
based on interpretation of topographic and geological
maps in scales 1:50,000 and 1:250,000.
However, from these maps, only the one drawn by Raisz
shows an image of the topography. In their map of
terrestrial provinces, regions and subregions, (Ortiz
Solorio et al., 1984), the limits between the provinces and
regions are represented with lines over the 1:1,000,000
DGG-INEGI topographic maps. The DGG-INEGI
physiographic maps represent the physiographic
divisions with lines, colors and codes, but they do not
include any portrait of the landforms.
Maps intend to offer an image of some aspect of some
region of the world. In most of the cases they show the
distribution of some specific feature or variable in a two
dimensional space. The shape of the Earth's surface, the
relief is represented normally in the topographic maps
through the contour lines; the elevation can be read from
them, and from the density patterns of the same
contours, some idea of the landforms can be obtained.
The relief however, can be better appreciated if it is
represented in a form that, at least, gives the impression
of a three dimensional space. Shading has been used as
one of the tools to give the perception of distance, shape
and volume, and in the case of maps, the shape of the
terrain. So far, in most of the cases the shading has
been done manually, resulting many times in beautiful,
and sometimes relatively realistic maps. But the
complexity of the relief makes almost impossible to
portrait all the topographic features and its details (Thelin
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
