Methods:
Data Preparation and Manipulation:
Sightings
Excel Lat-Long data was imported into ArcGIS as XY data and converted to shapefiles for all cetacean species. These shape files were then converted into Idrisi vector format using the SHAPEIDR operation in Idrisi. The sightings were rasterized using the RASTERVECTOR operation for further analysis. Cells were coded by the species code column in attributes table. This allowed cells to have different values for each species sighted in the given cell.
Tracklines
Data output from the Garmin GPS unit was in the form of GPX files. Tracklines were coverted to point shapefiles for use in ArcGIS using a DNR Garmin (a software bundle produced by the State Department of Natural Resources of Minnesota). This package allows for the converting of Garmin GPX output into shapefiles as well as converting between shapefile types (point, line, polygone). Furthermore, it allows the user to select the projection of the output shapefile. A WGS84_UTM-20N projection was used as both the GPS unit and the NOAA coastline data used the WGS84 Datum. The resulting shapefiles were converted to Idrisi Vector using the SHAPEIDR import operation in Idrisi.
Before converting all of the track point shapefiles to rasters, I created a blank raster using the INITIAL operation in IDRISI. In order to use grid cells which measured 500m2, I needed to input the maximum and minimum X and Y UTM coordinates for the raster grid. I converted the Lat-Long coordinates I desired into UTM XY using a conversion tool created by Steve Dutch at the University of Wisconsin-Green Bay. I divided the study area in 500 meter grid cells by dividing the horizontal and vertical distances by 500. This resulted in a grid of 9744 500m2 cells with 112 columns and 87 rows. Once the blank raster was created, the vector data were then converted to raster using the RASTERVECTOR operation, while selecting “change cells to record the frequency of points”. This option allows for the automatic calculation of the number of track points within each grid cell. As each point represents one minute of vessel effort, the frequency of points in a given cell equates directly to the number of minutes spent in that cell by the CW vessel.
Coastline
The coastline was imported into ArcGIS as XY data and converted to a pointshape file. DNR GARMIN was used to convert the point shapefile to a polygone shapefile for use in the maps.
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