GEODATABASE
Existing Data

Pre-existing digital data for the study area was fairly limited, especially in comparison to United States data volume standard, but there is some out there.  Probably the largest single entity supplying geo-spatial for Mexico (at least in mountainous southern Tamaulipas) is INEGI, both for digital and printed information.  INEGI (Instituto Nacional de Estadistica Geographia y Informatica) is a state run mapping agency for Mexico, and produces a wide variety of data products.  Many of these datasets are quite new, and although most of the country is well covered, there are still some remote areas that do not have many types of information available.  Such as the study area of Sistema Zacatón.   Paper topographic maps at 1:50,000 and geological maps at 1:250,000 are available for the entire study area, and have been imported to the GIS by using the georeferencing tool in ARC GIS.    INEGI also has some aerial panchromatic photographs that covers most of the study area except for the far northern reaches.  These have also been georeferenced similarly as with the paper maps, and overlain with other spatial data.  Other remotely sensed data comes from LANDSAT imagery that has been made available by the North American Land Coverage (NALC) dataset.  DLGs,  DRGs, DEMs, and DOQs are available from INEGI for the southern fringe of the study area, but not for the northern three quarters of it.   The DLG (digital line graph) for the southern quadrangle and a corresponding DEM were used primarily for viewing purposes.