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<br />{ <br />l <br />~ <br />j~ <br />f" <br />~. <br />'" <br />t: <br />~ <br />t <br />1,' <br /> <br />GEOGRAPHIC INFORMATION SYSTEMS <br /> <br />chris Brooks, P.E. <br />Jack Tidwell, AICP <br /> <br />Abstract <br /> <br />~: <br /> <br />The North Central Texas Council of Governments (NCTCOG) began using <br />Geographic Information Systems (GIS) nearly four years ago. NCTCOG <br />uses the ESRI ARC/INFO GIS software in many of its regional <br />programs. This system is currently being used primarily for <br />analyzing, processing, distributing and managing census, environ- <br />mental, transportation, land use and other regional data of <br />interest to NCTCOG and its local member governments. USGS Digital <br />Line Graph (DLG) and 1990 Tiger line flies arl~ the primary base- <br />mapping data used at this time. However, times: are changing. New <br />database structure and source file options are being pursued <br />through the execution of current work programs in the agency. This <br />paper focuses on a very important program and the role GIS is <br />playing in this effort. <br /> <br />In August 1990, the U.S. Army corps of Engineers (COE) and the <br />NCTCOG, representing nine cities, three counties and two special . <br />districts, entered into an agreement to conduct an 8.0 million <br />dollar Feasibility Study of the Upper Trinity River Basin. An <br />important goal of this project was a develop modelling tools that <br />would automate study processes, allowing more time and resources to <br />be devoted to the alternatives evaluation process. GIS was <br />logically seen as the primary vehicle to achieve this goal. One of <br />the most significant and costly elements of this; study involved the <br />development of accurate base mapping information. This <br />engineering-scale base mapping effort of the Trinity River corridor <br />covers more than 237 square miles of area ill the heart of the <br />Dallas-Fort Worth metroplex. Greenhorne and O'Mara, Inc. (G&O) of <br />Maryland was selected to produce the new base map of the corridor. <br />This contract involved establishing a consist:ent survey control <br />datum, delivery of digital topographic mapping files in intergraph <br />of ARC/INFO formats, and the generation of digital cross-sections <br />to be used in the hydraulic modeling. This base mapping must meet <br />National Map Accuracy Standards and will result in horizontal <br />accuracies of +/-4 foot and vertical accuracies of +/-1 foot at a <br />scale of 1"-200'. virtually all desirable plani.metric element have <br />been identified and captured in this mappinsr project. G&O is <br />approximately fifty percent complete with the total mapping effort <br />which will be completed by April 1993. The development of this <br />base mapping is very essential to the success of this study. This <br />data provides the hydraulic engineers with highly accurate and <br />consistent information so that improved floodplain models are <br />developed. <br /> <br />~" <br /> <br />'. <br />, <br /> <br />, <br /> <br />t <br />~. <br />!-~ <br />, <br />Ii <br />~" <br />I' <br />~. <br />, <br />f. <br />