Evaluación del Modelo de Elevación Digital oficial mexicano (Continuo De Elevación Mexicano, CEM 3.0) de INEGI

Abstract

The official Mexican Digital Elevation (MED), known as the Mexican Elevation Continuum (CEM 3.0), of the National Institute of Statistics, Geography and Informatics (INEGI) is evaluated by comparison with LiDAR elevation data in three representative areas of elevations in Mexico: 1) a hilly region with steep slopes and high elevations, 2) a coastal plain with gentle slopes and very low elevations, and 3) a transition zone with intermediate features. For the hilly and transition zone, both datasets show a strong similarity. However, in the plain the errors are very high (tens of times the value of the elevation), and the datasets do not show a linear regression. Apparently, these errors are due to an undocumented procedure applied by INEGI for the treatment of minor water bodies. Around these bodies, walls of hundreds of meters have been created, probably to force the drainage network to be directed to larger water bodies (instead, the recommended practice is for the drainage network to cross the water bodies). On the other hand, because INEGI truncates decimals in the CEM 3.0, large fictitious terraces with the same elevation are created, when in reality, there should be a smooth slope. Therefore, the true resolution of the CEM 3.0 is much lower than suggested by INEGI (pixel length = 15 m). Unfortunately, the described problems suggest that the use of CEM 3.0 is not recommended, especially in hydrological and hydraulic applications.