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Digitizing Software |
Digitizing Tablets |
Petroleum Software |
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Digitizing Maps Planimetering is commonly done by geologists and engineers when an areas of a map is needed. These areas are used in estimating reserves and areal extent of fronts. Historically, areas by hand were performed by counting the squares. Next, mechanical devices were used which would give the area of a closed surface. Although digital planimeters similar to mechanical planimeters are available, a commonly owned peripheral, the digitizing tablet, offers PC users the ability to "planimeter" with results stored on a computer. Once contours are stored as (x,y) coordinates and areas of surfaces computed, users can take these numbers for a variety of calculations. Planimetering using a microcomputer and tablet offers analysts an important tool for estimating areas from contour maps. Digitizing Maps To analyze maps, the maps must first be entered into the computer. In PLAN 2002 this is done by digitizing each contour using a digitizing tablet, a device attached to the computer’s serial port that transmits very accurate coordinates of a map, drawing or curve. As the user traces each of the map’s contours, a series of (x,y) coordinates defining the contour are sent from the tablet to the computer. Digitizing the contours form simple maps is straightforward but for more complicated maps several rules should be followed. First, map boundaries should be defined using the four corners of the map. This allows maps larger that the digitizing tablet to be digitized in sections (e.g. left half and then the right half). When the contours are digitized, the computed areas are limited to the map boundaries resulting in accurate contour areas. Second, all digitized contours must start and stop at the same point which PLAN 2002 automatically does by closing contours to form closed surfaces. Third, all of the contours defining the structure highs and lows should be digitized properly reflecting the true contour area for individual contours. Fourth, hill peaks and sinkhole low spots can be defined by digitizing point contours allowing appropriate incremental volumes to be added and subtracted. Once contours have been digitized, three methods are available for quality control. The first is redigitizing, which is also commonly used with mechanical planimeters. This provides for a contour to be digitized several time with the user selecting which contour to use for defining the map. If desired, an average of the different contours can be selected. The second quality control method is to print or plot the digitized map for overlay onto the original map. Any contours which may need to be edited can be redigitized. The third method of quality control is in comparing the volume calculations of the Modified Trapezoid Rule and the Vertical Slice Method. Mathematically these two volumetric methods should give the exactly the same results.
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