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Creating or Modifying Fire Planning Unit (FPU) GIS Shapefiles for Fire Program Analysis (FPA)
Fire Program Analysis (FPA) has specific GIS requirements for Fire Planning Unit (FPU) shapefiles. This document explains how to create, add, change, or delete features in an existing base FPU shapefile. See Updating Fire Planning Unit (FPU) Boundaries for further information about boundary update procedure.
1. Use ArcGIS (current agency version) to create or edit shapefile features. ArcGIS Help provides detailed instructions on how to create new features and edit the shapefiles. (See also Shapefile Creation )
Note: Communicate with your participating partner agencies when developing FPU boundaries to avoid unintentional gaps (slivers) or overlaps between common (coincident) FMU boundaries. Failure to do so may result in additional work for all partners later in the FPA data input process.
2. Ensure that the shapefile coordinate system is Geographic (decimal degree latitude/longitude) and the Datum is North American Datum (NAD 83). If your data are not Geographic NAD 83, contact your GIS Specialist for help in converting it.
3. Ensure all polygons in the shapefile are closed (complete). Any gaps in a polygon boundary will result in a "topology" error when the shapefile is uploaded to the FPA server. If you get this error and cannot identify or correct the problem, contact a GIS specialist for assistance.
Shapefile Creation
After finalizing your FPU polygon (or if you encounter "topology" errors when uploading the shapefiles), work with your GIS specialist to ensure that the shapefile is free from slivers and overlaps. The process of building or cleaning creates polygon topology (see Topology). When creating the FMU polygon, it is necessary to eliminate slivers, dangles, or undershoots from shapefile, and it cannot be done in ArcView 3.x. Once you have added the topology to the coverage, you must convert it back to a shapefile.
While multi-part shapes are acceptable, each FPU may only have one record in the attribute table. To accomplish this, you can merge polygons and in ArcMap, or use ArcToolbox to dissolve on the FPU_Name field.
Layer Verification
FPA cannot access shapefiles unless they adhere to these GIS data integrity rules:
- Verify that final FPU shapefile is created from a coverage that contained polygon topology built, or that it does not have gaps in the polygon boundaries. If you make significant or multiple edits after following the processes in Shapefile Creation , you may have to convert the shapefile back to a coverage and use ArcMap or ArcInfo to build or clean the coverage, then convert it back to a shapefile.
- Eliminate overlaps and slivers (unwanted gaps) between polygons. Doing so results in a cleaner FPU file and prevents double-counting of acres.
- Ensure that all the required attribute fields are correctly defined and are populated (have values assigned).
Topology
Topology describes the spatial relationships between adjacent features, and uses x, y coordinates to identify the location of a particular point, line, or polygon. Using such data structures enforces planar relationships, and allows GIS specialists to automate error handling, to reduce artifacts from digitization, and to reduce the file size required for storing the topological data.
(See Types of GIS Topology for examples of different topologies.)
Non-contiguous FPUs
You may have non-contiguous FPUs, which are multi-part shapes that contain multiple polygons with just one data record in the DBF file. To reduce a multi-part FPU to a single record in the DBF, perform a GIS dissolve using the FPU_Name field (assuming that all polygons are labeled with the same FPU name.) Contact your GIS Specialist for further information about completing this process.
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