Geologic Map of the San Marcos North Quadrangle and Adjacent Portions of the Mountain City and San Marcos South Quadrangles, Hays, Caldwell and Guadalupe Counties, Texas.
Date
1976
Authors
Grimshaw, T.W.
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Abstract
Digitally redrafted and georeferenced color version of the 1:24,000 paper geologic maps contained in Grimshaw, T.W., 1976, Environmental geology of urban and urbanized areas, a case study from the San Marcos area, Texas [Ph.D. thesis], Austin, Texas, The University of Texas at Austin, 244 p. Scale 1:24,000.
Department
Description
“Process Steps:
1. Black and white paper copies of the 1:24,000 geologic maps in the 1976 Ph.D. thesis of T. W. Grimshaw were scanned, assembled into a single map and saved in Tagged Image File Format (tif) at 200 dpi and the original map size, then georeferenced in ArcGIS desktop ArcMap v. 10.1 to North American Datum 1983 geographic coordinates. Line work was digitized in heads-up mode, a map topology was created, and rock unit polygons were constructed and attributed with ArcGIS tools.
2. Digital base map data for the geologic map were assembled from the following US Geological Survey online sources: a) Roads, boundaries and structures from the National Map, 2013; b) Place names from the Geographic Names Information System, 2013; c) Hydrography from the National Hydrography Dataset, 2010; d) Elevation Data from the National Elevation Dataset, 2004. Base map contour lines and spot elevations were obtained from the Texas Natural Resources Information Service (TNRIS) in 2010. Vector base layers from these sources were edited where necessary to conform to locations displayed in one meter resolution digital orthophotos of the region in 2010 provided by TNRIS.
3. The completed vector geologic map and base layers were exported from ArcMap as collared and collarless jpeg images after projecting on-the-fly to the spatial references of interest (see below). World file coordinates were obtain by georeferenced these images and exporting them with referencing information in TIF format. KML (KMZ) and geoPDF versions of the map were created directly from the vector layers with options and tools in ArcGIS.
Files in this work contains four different georeferenced versions of the original map. The versions, as distinguished by Download File name, are: 1) San_Marcos_GCSWGS84_collarless.zip: zipped files that include a collarless map in TIFF format and ancillary ArcGIS v. 10.2 georeferencing files and metadata. The spatial reference is geographic coordinates relative to the WGS84 datum; the map is unprojected. 2) San_Marcos_UTM_collarless.zip: a zipped file that includes a collarless map in TIFF format and ancillary ArcGIS v. 10.2 georeferencing files and metadata. The spatial reference/projection is UTM zone 14 relative to the NAD27 datum. 3) San_Marcos.pdf: a GeoPDF of the full collared map referenced/projected to UTM zone 14 coordinates relative to the NAD83 datum. 4) San_Marcos.kmz: a KML version of the collarless map for viewing in Google Earth. The spatial reference is geographic coordinates relative to the WGS84 datum. Further metadata for each map version are available in Federal Geographic Data Committee ( FGDC)-compliant metadata file within the zip files and in the document Properties of the GeoPDF and KML files when opened in Adobe Acrobat or Google Earth.
Files in this work contains four different georeferenced versions of the original map. The versions, as distinguished by Download File name, are: 1) San_Marcos_GCSWGS84_collarless.zip: zipped files that include a collarless map in TIFF format and ancillary ArcGIS v. 10.2 georeferencing files and metadata. The spatial reference is geographic coordinates relative to the WGS84 datum; the map is unprojected. 2) San_Marcos_UTM_collarless.zip: a zipped file that includes a collarless map in TIFF format and ancillary ArcGIS v. 10.2 georeferencing files and metadata. The spatial reference/projection is UTM zone 14 relative to the NAD27 datum. 3) San_Marcos.pdf: a GeoPDF of the full collared map referenced/projected to UTM zone 14 coordinates relative to the NAD83 datum. 4) San_Marcos.kmz: a KML version of the collarless map for viewing in Google Earth. The spatial reference is geographic coordinates relative to the WGS84 datum. Further metadata for each map version are available in Federal Geographic Data Committee ( FGDC)-compliant metadata file within the zip files and in the document Properties of the GeoPDF and KML files when opened in Adobe Acrobat or Google Earth.