detailed portrait of the topography that the relief maps 
offer. 
Mexico is one of the most heterogenous countries. For 
example in biological diversity, it is thought that around 
30,000 species of vascular plants exist in Mexico 
(Rzedowski, J. 1991). There are more species of pines in 
Mexico than in any other country (Perry, J.P., 1991). The 
climate varies from humid tropical to dry tropical and to 
temperate and arid. And so varies the vegetation. From 
tropical rain forests to various types of temperate forests, 
grasslands, scrublands and deserts. The reasons for this 
diversity are several. Two great biogeographic regions 
meet in Mexico: the Neartic and the Neotropical: so 
species and/or group of plants from both regions exist 
here. There is also an important component of native 
plants; (Rzedowski, J. 1991). Climatic heterogeneity is 
also one of the most important factors for the diversity. 
Topography acts in fact as the major single factor 
controlling the spatial climatic variations in Mexico 
through elevation and effects like rain shadow. 
Early in the primary (elementary) schools, children learn 
that Mexico is a country with a great variation in 
landforms: mountain ranges, plateaus, plains, valleys. 
However, the usual school maps show the relief in a 
schematic, generally poor way, and most of the 
information is only textual, sometimes including 
photographs of important features. Now students could 
have access to this relief map series of the whole 
country. The maps could be distributed in a massive way 
in schools through the educational system. 
As the shaded image can be combined virtually with any 
other image, shaded maps of any theme can be 
prepared; topographic, climatic, geological, soils, 
vegetation, etc. The combination of thematic information 
and the shaded relief can help not only to make better 
looking maps, but also to learn about relations between 
the different features and phenomena with the relief. 
The shaded image and the DEM can also be registered 
and mixed with Satellite images for enhancement. For 
example with low resolution images like those from the 
AVHRR (Advanced Very High Resolution Radiometer) 
sensor, relief shading can help to improve them for visual 
appreciation (transforming the RGB image to IHS, then 
taking the shaded image as intensity an transforming it 
back to RGB). Elevation information can be included by 
color coding it in the images, (Toutin. T, and B. Rivard, 
1995). 
Prospects. 
Some other derived maps from the DEM can be obtained, 
like slope and aspect maps. Quantitative studies of 
landforms, and improvement of climatic maps are 
possible by modeling the influence of elevation and relief 
on temperature and precipitation. 
New, improved versions of the relief-series maps wiil be 
developed, as well as maps at greater scales. A map 
series in scale 1:2,000,000 is attainable using the images 
produced in this work. Considering the 500m resolution, 
the pixel size in the printed map at this scale would be 
0.25mm. For a scale of 1:1,000,000 a resampling of the 
original DEMs to a resolution of 125 or 250 meters would 
be needed. The DEMs derived from the topographic map 
series scale 1:50,000 make possible to obtain relief maps 
with much greater detail and accuracy, at scales like 
1:250,000 or larger. 
Finally, besides the technical issues that have been 
discussed, the shaded relief maps offer also a different 
way to appreciate and enjoy the beauty of the Earth. 
SELECTED BIBLIOGRAPHY. 
Burrough, P.A. 1986, 
information systems 
Principles of geographical 
Cuanalo de la Cerda H., E. Ojeda Trejo, A. Santos 
Ocampo, and C.A. Ortiz Solorio, 1989, Provincias, 
Regiones y Subregiones Terrestres de México. Colegio 
de Posgraduados. Chapingo, México. 
Ortiz Solorio C.A., H.E. Cuanalo de la Cerda, E. Ojeda 
Trejo, A. Santos Ocampo. 1984. Carta de Provincias, 
Regiones y Subregiones Terrestres de la Republica 
Mexicana. Colegio de Posgraduados. Chapingo, México. 
Perry, J.P., 1991. The Pines of Mexico and Central 
America. Timber Press. 
Pike, R.J. and G.P. Thelin, 1992. Building a Better Map. 
Earth. Pp. 44-51. 
Raisz, E., 1964, Landforms of Mexico. 2nd. ed. 
Cambridge Mass. (Map at scale about 1:4,000,000 and 
explanatory text). 
Rzedowski, J., 1991, Diversidad y origenes de la flora 
fanerogamica de México. Acta Botanica Mexicana 14, 
pp. 3-21 
Thelin, G.P;, and R.J. Pike, 1991. Landforms of The 
United States - a Digital Shaded-Relief Portrayal. United 
States Geological Survey, Miscellaneous Investigations 
Series. Map Y-2206 (Map and explanatory pamphlet). 
Toutin, T. and B. Rivard, 1995. A new tool for Depth 
Perception of Multi-Source Data. Photogrammetric 
Engineering and Remote Sensing, vol. LXI(10), pp. 1209- 
1211. 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996