FLOOD00228

• County: Statewide
• Community: All
• Stream Name: All
• Title: ASFPM Abstracts, etc. 1993
• Date: 1/1/1993
• Prepared For: ASFPM
• Prepared By: ASFPM
• Floodplain - Doc Type: Educational/Technical/Reference Information

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DIGITALLY PRODUCED FLOOD INSURANCE RATE MAPS

Sue Hoegberg
David Maune

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Abstract

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Digital Flood Insurance Rate Maps (DFIRMs) are FIRMs created from
digital files. They emulate the FIRMs produced using traditional
manual cartographic procedures, but are readily updated,
transferred and stored. In addition, they allow for some
innovative cost savings such as positive printing processes and the
possibility of print-on-demand.

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Digital data to create the DFIRMs comes from several sources. Base
map files may come from other federal agencies (u.s. Bureau of
Census, u.s. Geological Survey) or state, count~' or local agencies.
These files may have some variety of graphic presentation, although
many depict road networks with single lines. FIS data files may
come from FEMA's Digital Flood Data Overlay (DFDO) files in DLG
format, study contractor submission, or other local agencies with
whom FEMA has entered into cooperative agreements.

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The data is combined from the various sources and put into a common
projection. Patterns are applied to certain features, such as
railroads and political boundaries. Lineweights are assigned to
road features based on the road classification (primary, secondary,
tertiary). Text is placed to identify features; symbols such as
cross section hexagons are assigned to feature that require them;
and patterns are added to Special Flood Hazard Areas.

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The final files are plotted on a high-quality plotter capable of
reproducing the screens and outputing large size maps.

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The application of new technology to FEMA I S traditional map product
opens the avenue for changes to the look of the maps to take
advantage of the technology. One of these is the use of line
screens instead of dot or biangle screens. This allows for
printing the maps from positive plates instead of negatives.
Another new approach is the possibility of moving the Elevation
Reference Mark descriptions to a new border column. These new
approaches and more will be considered as DFIID~s are produced and
updated.