Availability of Digital Geodata in Mexico

Availability of Digital Geodata in Mexico

Dirk Masuch Oesterreich

During the last ten years Mexico has made great efforts in producing and publishing digital geodata at a country wide scale through several government agencies and private enterprises. Three of these entities, two of them governmental and one private, are introduced hereafter.

The principal source of statistical data, maps and georeferenced data is the National Institute for Statistics, Geography, and Informatics (INEGI). Through its network of state offices, INEGI is responsible for data collection, data update and maintenance, and publication of these data at regional and national scales. Geographic information is available in both conventional paper and digital formats.

The standard map scales for topographic information are 1:50000 and 1:250000 in UTM coordinates, covering the entire country. Digital data are available for almost 100 % of the country. The preferred data formats are shapefiles and dxf for vector data and bil and grid files for raster data, respectively. Digital data are identical to the map scale and map area of the respective paper maps.

Orthophotos are available at a scale of 1:20000 covering a great part of the country. Prices are low for the paper maps and moderate to low for digital data. Basic topographic vector data are available for free download at a scale of 1:1,000,000. 30 meter DEMs covering the entire country are also available at no cost at http://www.inegi.gob.mx.

INEGI also provides municipal vector data of very high detail, which unfortunately are not made available to the general public. Extensive working experience with INEGI digital data confirmed a generally high quality of both raster and vector data. Occasionally, confusion arises as to the projection parameters of the digital data. Former Mexican geographic data were referenced to the NAD27 datum. Recent maps are exclusively referenced to the ITRF92 datum. Since the difference between these projections in Mexico is roughly 30-35 meters horizontally and 200-205 meters vertically, projection parameters have to be checked and data have to be reprojected, if necessary.

Geological and geophysical data and maps are produced and made available by the Mexican Geological Survey (Servicio Geologico Mexicano, the former Council of Mineral Resources). The standard map scale for paper maps and digital data is 1:250000. The entire territory of Mexico is already covered by digital geological maps at that scale. The geological map at 1:50000 is progressing quickly.

Geological and geophysical maps are free to download in pdf format in the cartas section of the productos menu at http://www.coremisgm.gob.mx. Digital geologic information is available as ArcInfo coverages or shapefiles, consistent with the area covered by the respective paper map. Digital data are distributed on CDROM by the state offices and unfortunately must be considered expensive.

The exclusive Mexican distributor of ESRI products is a company called SIGSA, located in Mexico City. SIGSA also provides basic topographic data, all sort of digital imagery, and elevation data at various scales and resolutions. Their “Project Mexico” provides data for the whole country at national, state, and municipal levels at scales as high as 1:5000. Mexico’s three major cities (Guadalajara, Monterrey, and Mexico City) are covered at a 1:1000 scale. Information is available at http://www.sigsa.info. Prices for data and consulting services are available only on request and are not necessarily to the cheap side.

( Digital Geodata for Mexico )

( Servicios HidroGIS )