Marine Resources Assessment for the Marianas Operating ... - SPREP

AUGUST 2005 FINAL REPORT
or information extracted from a literature description are referenced as source information. In certain
cases, source maps and/or information had to be interpreted to be usable in the GIS environment. Maps
displaying geographic information that was interpreted or altered from the original source map/information
are noted in the figure caption as being “adapted from” that source.
The source type and associated references for all marine resources data presented in the map figures
are listed in each figure’s caption. The full reference citations for map source data or information may be
found in the Literature Cited section of each MRA chapter. The two primary types of spatial information
used in the Marianas MRA were coordinate data and scanned maps. These two source types are
associated with differing levels of data reliability or confidence (Appendix A-1 contains a further
explanation of data confidence). Numerical or authentic data are associated with the highest level of
reliability, while data obtained by scanning source maps are less reliable.
Problems were encountered when data sets were combined during the development of the map figures.
Source data were not in a standard format, there was no standard naming convention for species names,
and some data sets included missing or unlabeled data fields. To mitigate these difficulties, many steps
were taken to standardize and control the quality of the numerical data, especially for the marine mammal
and sea turtle data. Prior to using the data, a master database was created in Microsoft ® Access where
the data format was standardized so that the data could be merged and later used in the GIS. To
accomplish this, data were manipulated to match data set records with a set of standard field names. In
some cases, the latitude and longitude had to be converted to decimal degrees with accuracy to the
fourth decimal place. Species’ common names were added to the database to replace the multiple
species codes that accompanied the original data. The different types of codes used for species names in
the original data sets were not always consistent from one data set to the next. Compiling a
comprehensive list of species names increased the chances of plotting all sightings for a given species on
the map figures. To maintain the integrity of the original data, all fields and records were kept without
alteration. When necessary, fields were created to store supplemental information or data that was
altered from the original source. No original data fields were deleted and all added fields are signified by
the “GMI_” prefix (GMI: Geo-Marine, Inc.). For example, source fields were added to the main data set to
indicate the origin of the data and are shown in the field as “GMI_source.”
GIS data are displayed as layers or "themes" for which scale, extent, and display characteristics can be
specified. Multiple themes are represented on an individual map figure. Throughout the project, data
imported into ArcView ® had to be maintained in the most universal, least transformed manner in order to
avoid conflict between theme coordinate systems and projections. In the GIS, the most flexible spatial
data format is the unprojected geographic coordinate system, which uses decimal-degree latitude and
longitude coordinates (Appendix A-2 contains more information on map projections). The decimaldegree
format is the only coordinate system format that allows unlimited, temporary, custom projection
and re-projection in ArcView ® and is, therefore, the least restrictive spatial data format. The printed maps
and electronic GIS map data for this MRA report are unprojected and are not as spatially precise (in
terms of distance, area, and shape) as a projected map. Consequently, the maps should not be used for
measurement or analysis.
Once the marine resources data were imported and stored in the GIS, maps were created representing
multiple layers of either individual or combined data. Maps in this report are presented in several different
forms and scales, depending upon the marine resource in question. Full-page maps of the entire study
area region, from FDM to the southern boundary of Warning Area W-517, are at the approximate scale of
1:3,289,000. At this scale, it is difficult to visualize the distributions of marine resources that are located in
nearshore environments. As a result, a number of maps include zoomed in views of Guam, Tinian, and
FDM so that the locations of certain coastal resources in Apra Harbor, Agat Bay, off Andersen Air Force
Base, and around Tinian and FDM can be more easily viewed. The maps in this MRA report are
presented in both kilometers and nautical miles.
The ability to display and analyze multiple data themes or layers simultaneously is one of the advantages
to using a GIS rather than other graphic software. Customizations were made to the software in Avenue ® ,
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