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recognizes that despite FEMA' s best efforts to make the FIRMs as useful as possible, the descriptions of SFHA areas, as depicted by some maps, may, in some instances, not be clear enough to permit lenders to decide with certainty and precision whether or not property which is the security for a loan or which is the subject of financial assistance is located in such an area. It is for this reason that FEMA has recommended a "good faith standard." The good faith standards require lenders to exercise "due diligence and good faith" in determining the location of a property which is the subject Q~._~ loan relative to areas of special flood hazards as shown on a FIRM. This guidance is further explained, with additional information on the 1973,'Act in FEMA Publication 186, October 1989, "Mandatory Purchase of Flood Insurance Guidelines." When determinations are being made by lenders, or firms or individuals retained by lenders to assist in these endeavors, collateral data in addition to the FIRM is frequently required. FIRMs do not include all roads within communities, nor dp they depict address, property boundary, or structure location information. As a result, determinations frequently can only be made by using an ancillary source of data, such as a land parcel map, to determine the location of a property on the FIRM. Digital address range data, land parcel, and structure information is available for many conununities across the Nation. Using these digital data and GIS technology, it is possible to make determinations relative to the 1973 Act, and meeting the Good Faith Standard. However, the lenders must assure that due diligence and good faith is exercised in application of digital mapping systems to make determinations. Because of both the increased complexity and analytical capabilities of GIS, assuring compliance with the good faith standard may require additional effort relative to use of paper maps. A prime concern is to assure accuracy of the digital base map and structure location data are appropriate for use with DFIRM data to make determinations relative to the 1973 Act. The concern for accuracy of the ancillary data used with DFIRMs should increase in direct proportion to the relative closeness of the property under analysis to the SFHA boundary. Thus, lenders might not find it to be prudent to use digital data at the 1:100,000 scale as the primary source of information upon which to make a determination regarding a property located within 200 feet of a SFHA. such caveats should be carefully considered when U.S. Bureau of the Census TIGER line file address range data is used as the source from which property determinations will be made. In some instances, GIS will enable the use of large scale land parcel, topograph- ic, structure, and other information, with DFIRMs to make determinations. GIS technology allows maps to be created at any user specified scale. Enlargement of scales does allow for precise determinations to be made. However, precise measurements are not inherently accurate. Accuracy can only be assessed from an appraisal of the quality of source data. As noted previously, SFHA boundary information conveyed by DFIRMs was developed to overlay USGS 7.5-minute topographic maps at a scale of 1:24,000. Thus, DFIRM data cannot be assumed to have an accuracy of better than 40 feet. Due to other limitations inherent in DFIRMs, FIA recommends that determinations using GIS technology and DFIRMs generally be made only when structures are located 50 or more feet from a SFHA boundary. In these cases, data such as the BFE determined from a FIS flood 10/93 v