Posters - IGWS

Permanent link for this collectionhttps://hdl.handle.net/2022/421

This series is comprised of maps and topical posters, usually containing a combination of photographs and graphics. Typically educational in nature, they are intended for a public audience. Posters go through a full formal review, are usually commercially offset printed in large batches, and are sold through the IGWS Bookstore.

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Browsing Posters - IGWS by Subject "Berrien County, Michigan"

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    Dressing the Emperor: The Role of GIS in the Development of Three-Dimensional Hydrogeologic Models
    (2006-11-20) Letsinger, Sally L.; Olyphant, Greg A.; Medina, Cristian R.
    The U.S. Geological Survey (USGS) (2001) mapped structure contours for the tops of each of 20 individual units in intersecting and overlapping glacial morphosequences in Berrien County, Michigan (1,350 km2), as part of the mapping program of the Central Great Lakes Geologic Mapping Coalition (CGLGMC). We have developed a methodology to translate this detailed morphostratigraphy first into a solid three-dimensional geologic model, and then into a three-dimensional block of data that can be used as input to a finite-difference groundwater-flow model. The technique involves a hybrid approach involving geographic information systems (GIS), three-dimensional information visualization software (3DIVS), and customized data-processing code. The methodology begins by converting Stone’s structure contours (they are attributed vector contours) for each individually mapped unit into a raster surface at a defined grid resolution (200 m x 200 m). The top of the geologic model is the surface topography (digital elevation model), which is also used to derive the drainage network that is an important boundary condition in the groundwater-flow model. The bottom of the geologic model is the bedrock topography, which was also mapped and contoured by USGS (2001). Stone constructed his structure contour model such that the bottom of each map unit is described by the surface contours of the unit that lies immediately below it. Complex interrelationships dictate that the tops of a number of individually mapped units are sometimes required to describe the bottom surfaces of laterally more extensive units. Once all of the requisite raster grids have been derived, they can be manipulated to provide input that is necessary for development of a detailed solid geologic model using 3DIVS. GIS software and custom code are also used to assign hydrogeologic attributes to the elements of the final three-dimensional finite-difference geologic model.
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    Dressing the Emperor: The Role of Three-Dimensional Information Visualization Software in the Development of Three-Dimensional Hydrogeologic Models
    (2006-11-20) Medina, Cristian R.; Olyphant, Greg A.; Letsinger, Sally L.
    The goal of this research is to develop a model that describes the saturated and unsaturated groundwater flow in Berrien County, Michigan (1,350 km2), an area containing a complex sequence of glacio-lacustrine deposits. Stone and others (2001) mapped the morphosequences in Berrien County at a scale of 1:24,000, which includes georeferenced structure contours for 20 individual units. We have developed a methodology to translate this detailed morphostratigraphy into a solid three-dimensional geologic model, and then into a three-dimensional block of data that can be used as input to a finite-difference groundwater-flow model. Letsinger and others (2006) describe the process of using geographic information system software to convert the structure contours into georeferenced raster layers that describe each unit. At this stage of the reconstruction, only the bounding surfaces between the units are defined. In order to stack the units in vertical space using customized computer code, a “virtual well field” (regularized two-dimensional array of points) samples each x-y location in each of the 20 rasterized data layers. Units that are intersected from the top bounding surface (surface topography) to the bottom bounding surface (bedrock surface) are then identified. The result of this step is a vector (one-dimensional array) at each virtual well location that describes the elevation of each morphostratigraphic unit boundary intersected at that location. However, at this stage, the model is essentially a regularized three-dimensional point cloud, and three-dimensional information visualization software (3DIVS) is then utilized to generate a solid geologic model by interpolating the vertical geologic “samples” throughout the model domain. A finite-difference grid (“brickpile”) at the chosen resolution of the groundwater-flow model is then generated from the solid geologic model using data-processing functions of the 3DIVS.