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<br />profile and the sucveyed lowest adjacent grade and/or lowest flooc elevation, <br />appropriately shou:~d be used to make a determination. <br /> <br />Prudence may requice that a more conservative margin than 50 feet: be used to <br />determine the need for ancillary data to support a GIS determination. Terrain <br />variations, the nature of flood hazards in the area, and the quality of all <br />digital data being. used to make the determination should be con:sidered ,",,'hen <br />establishing the nE~ed for collecting survey and flood profile data. <br /> <br />An example of the U:3e of the good faith standard for making determinations is the <br />development of guidelines for the use of FloodView, a DFIRM visualizcltion t.ool <br />to be distributed with NFIP CD-ROM digital mapping products. FloodView \0,111 <br />display DFIRM data overlaid on U.S. Bureau of the Census Tiger line file data. <br />Due to horizontal accuracy limitations of TIGER line file data, FloodView <br />software will alert. users whenever there are multiple flood risk zone:; within a <br />minimum 250 foot radius of the location of interest to the user. A screen <br />message will advise users that multiple hazard zones exist within close proximity <br />to the location of interest under such circumstances. Guidance on. app1icat:ion <br />of the FloodView software tool advises users to refer to other data if ,i prOpE!rty <br />determination is required within such proximity to the SFHA. <br /> <br />Revisions and Appeals of DFIRMs <br /> <br />The DFIRM thematic data is simply a digital version of the source hc1rdcopy FIRM. <br />Increasingly, hardcopy FIRMs are being generated from the DFIRM., Thus, any <br />revisions, appeals, or other requests for changes to DFIRMs can be m,ide under the <br />same mechanisms as those developed for the hardcopy format FIRMs. The only <br />change the DFIRM re:?resents is the format of the data. Existing NFlP rE!gulati.ons <br />and procedures are not impacted by this change. However, the end user does have <br />the option of submitting requests for revisions to FEMA in a digit.al format. <br /> <br />Physical Format of DFIRMs <br /> <br />DFIRMs in the USGS OLG-3 will be made available on Compact Disc - Read Only <br />Memory (CO-ROM) format. These discs will be compatible with the ISO 9660 <br />standard for CD-ROMs. CD-ROM drives and interface kits supporting this data <br />standard and compa.tible with PC technology are commonly available in the <br />marketplace. FEMA does not plan to supply these data on any other m4!dia, !3uch <br />as magnetic tape, floppy disks, or similar technologies. <br /> <br />10/93 <br /> <br />vi <br />