Read Me

Read Me for the Seamap Bottom Oxygen Data Set

This README lists the data products available on this CD and explains the file naming conventions used. This file also explains the use of three scripts included with this project: the first two allow you to change the legend colors for the data sets and the coastline, and the third allows you to easily export all data sets as PostScript or JPEG images.

Note: This CD is intended for archival purposes. If you would like to work with the included files, you should copy them to your hard drive first. After copying the files, you may need to change them from being "read only" to being writable. In Windows NT, you can do this by right-clicking on the file in the explorer, selecting "Properties" from the popup menu, and unchecking the "read only" box in the properties dialog box.

List of files and directories

Here is a map of the directories and data files:

oxygen.apr (file)

An ArcView project file for viewing the included data sets.

samples (directory)

Contains the raw SEAMAP point (sample) data in ArcView shapefile format. Each point is a separate data record that represents a single sample.
There is one data set that contains all records available called envall.shp. As specified by the ArcView shape file format, there are several "helper" files that accompany the *.shp file, including envall.dbf, envall.shx, envall.sta, and envall.sts. All of these files must be kept together to use the envall.shp point file.
The envall data set has been divided into smaller data sets by year. These data sets are named using the four-digit year and the *.shp extension (e.g., 1996.shp). These are also accompanied by the various "helper" files of the same name.

contours (directory)

This directory contains contour files derived from the OXYMAX field in the SEAMAP data files. The OXYMAX field records the bottom oxygen measurement for each sample.
Two contours were created for each year: a summer (June and July) contour and a fall (October and November) contour. (There are a few years, particularly in the early 1980s, for which there were no data for summer and/or fall).

Naming convention: for summer, oxy_sYY where YY is the last two digits of the year.
Naming convention: for fall, oxy_fYY where YY is the last two digits of the year.
Example: oxy_s97 and oxy_f97 for summer and fall of 1997, respectively.

These contours are in ArcView GRID format; a GRID is actually a collection of files contained within a directory. All of these files must be kept together in that directory.
For each contour, there is an accompanying text file which contains some summary information for the contour (e.g., the cruise and vessel numbers involved, the number of points used, and so on).
This directory also contains two legend files, surface.avl and samples.avl, which contain the map legend definitions used for contours (surfaces) and points (samples) respectively.
For summer 1996, an additional data set was created: the middle depth oxygen values were contoured to create the file oxy_s96m. Another GRID file, named o_s96mb, is the difference between the middle and bottom oxygen values for the summer of 1996 (o_s96mb = oxy_s96m - oxy_s96, or delta = middle - bottom).

images (directory)

This directory contains the maps for each contour (summer/fall year), exported as JPEG and PostScript (eps) format.

summaries (directory)

This directory contains dBase format files which list the areas (in square kilometers) of different bottom oxygen zones. These zones where created by grouping together all of the values within a particular range. This table explains the fields in the summary tables:

oxy_code	count	sum_area	range
This is simply a unique number that identifies the summary zone. Its value corresponds to the upper end of the group's range.	The number of pixels (in the GRID format, these are called cells) that fall within this group's range	The total area of pixels that are within this group's range.	The range of bottom oxygen data values which defines this group. The groups were created using these ranges: > 0 - 2 > 2 - 4 > 4 - 7 > 7 - 10 > 10

The files are named using the following convention:

oxy_ + (s or f) + (YY) + sum.dbf, where

(s or f) is the letter s or f, for summer or fall.
(YY) is the last two digits of the year.

Example: oxy_s97sum.dbf is the summary file for the summer of 1997.
An extra file for the middle depth values for 1996 is included also: oxy_sum96msum.dbf

coast (directory)

Contains the coast shape file (coast.shp) and associated files. The coast file is used in the maps to show the land.

Utility scripts included in the ArcView project

The oxygen.apr project file contains two utility scripts which can be accessed through menu items when viewing the maps:

Change Legend Colors - This script is accessible from the "Utilities" menu when looking at the View or Layout of a particular map. When you select this menu item, you will be prompted by a dialog box to enter RGB values for the colors used in the legends for the samples (points) and the contours (surfaces). Note that the change will automatically be applied to the corresponding legends for all years. This insures that the same color scheme is used on all maps.
Change Land Color - This script is accessible from the "Utilities" menu when looking at the View or Layout of a particular map. This scripts is essentially the same as Change Legend Colors, except that it changes the legend color for the the called "Coast" which depicts the continental land mass.
Export Layout - This script is accessible from the "Utilities" menu, but only when viewing the map layout (the version of the map which includes, legends, captions, north arrow, etc.). This will export the layout as either a JPEG or PostScript (eps) file.