The General Bureau of Geography, established in 1968, prepares maps of Mexico, carries out studies of the national territory and provides national inventories of natural resources and infrastructure, as part of the National Geographical Information System.
INEGI developed the soils map of Mexico using units of classification related to the 1970 FAO/UNESCO soil map of the world, and modified by the Directorate of the geography of the national territory (DDGTENAL). In addition to the soil classes, the map units may be described by a chemical or physical phase. Chemical phases include salt, sodic, salt sodic, and without chemical phase. Physical phases include concretions, duripan, fragipan, gravel, Lithic (rock), stony, petrocalcic, petrogyp- sic, and without physical phase.
For more than 25 years the thematic cartography has been made featuring the characteristics of the national territory and the location of natural resources.
Selection of work area corresponds to a page of the map n preparation (one degree of latitude for every two degrees of longitude on a scale of 1:250 000).
Collection and analysis of information. Information on the soil and work area is analyzed using specialized bibliography.
Analysis of the existing map. The page to be reviewed/updated is studied to determine the areas that are likely to be changed and/or corrected.
Preliminary field inspection. This involves making a general tour of the work area to examine existing features and their characteristics, for example, the particular properties of soils.
Interpretation. Taking into account field observations and the references analyzed.
INEGI specialists fly over the national territory on board aircraft equipped with metric cameras that provide an exact register of land features such as mountains, rivers, vegetation, cities and communication routes.
Photographic prints are then subjected to photogrammetric techniques to eliminate distortions caused by lens curvature, irregularities on land, the altitude at which photos were taken, and the aircrafts speed. The The process continues with photo interpretation to identify the features in a photograph, which are corroborated through field work to provide an accurate, updated product.
Verification of field information and the results of sample analyses provide specialists with a broader grasp of the area under study. Source materials (photographs, images) are analyzed and interpreted again and information is corrected or added to the new map. Specialists observations on the specific features found in the work area are included, together with the results of sample analyses.
The features traced or delimited on the photographs or images are either transferred to a base map (the corresponding topographical map) and/or digitalized for subsequent incorporation into geographical data base and the National Geographical Information System.
The map in digital format is edited to give it the appropriate representation (colors, line types, typesetting, and symbols, among others) and is then printed. The two processes are effected using interactive digital equipment.
The products generated in Thematic Cartography are 1:250 000 and 1:1 000 000 scale printed maps.
Fases quimicas Chemical phases Salina Salt Sodica Sodic Salina sodica Salt sodic Sin fase quimica Without chemical phase
They are present in at least part of the soil, at a depth less than 125 cm.
The salt phase has soluble salts, with electrical conductivity of 4 mmhos/cm or more.
The sodic phase indicates a saturation with exchangable sodium of more than 15%.
The salt sodic phase refers to the presenence of both the salt phase and the sodic phase.
Clases texturales Texture classes 1 Gruesa 1 Coarse 2 Media 2 Medium 3 Fina 3 Fine
Fases fisicas Physical phases Concrecionaria Concretions Durica Duripan Fragica Fragipan Gravosa Gravel Litica Lithic (rock) Pedregosa Stony Petrocalcica Petrocalcic Petrogypsica Petrogypsic Sin fase fisica Without physical phase
They are present in at least part of the soil, at a depth less less than 125 cm.
The salt phase has soluble salts, with electrical conductivity of 4 mmhos/cm or more.
The sodic phase indicates a saturation with exchangable sodium of more than 15%.
The salt sodic phase refers to the presenence of both the salt phase and the sodic phase.
Clases texturales Texture classes 1 Gruesa 1 Coarse 2 Media 2 Medium 3 Fina 3 Fine
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