Hi Sherilyn,

Thanks for your interest in MGET. The Calculate Species Diversity Index for Polygons tool is designed for the scenario where you have a bunch of points scattered across a region and you want to divide the region into study sites defined by polygons or a grid defined by cells and a calculate diversity index value for each site or grid cell. Each point represents an observation of a species, optionally with a count of the number of individuals observed (the count is only required for certain diversity indices).

It sounds like you have line transect survey data for several study sites, in which a diver or ROV swam the transects at each site and recorded locations and species of coral. If those sightings are in the form of points, then you can calculate diversity for each site by creating a polygon layer that has a polygon surrounding each site. If you do not have a polygon layer, I suggest you try the Minimum Bounding Geometry tool that comes with ArcGIS (under Data Management à Features). This tool allows you to create bounding rectangles or convex hulls that enclose your features of interest (i.e., the coral points). If the coral points have a field that defines the study site, you can use the Group Option and Group Fields to tell the tool to create one polygon enclosing the points for each site. That is what you will need for the MGET Diversity tool.

Once you have that polygon layer, add a field to it to receive the diversity index value (use a FLOAT or DOUBLE data type). Then use the MGET tool. Give it the points and the polygon layer. You’ll have to tell it which field of the points holds the species ID, and which field of the polygons should receive the diversity index value. Pick the diversity index (see Wikipedia for some descriptions).

If for some reason you do not have points, you only have polylines, you will have to convert them to points. There are easy tools for doing that, but before I recommended anything, I’d want to know what the fields were of the polylines. It is standard to store transect effort lines as polylines but not standard to store species observations as polylines, unless the lines represent a summary for the transect (e.g. counts of species observed along the entire transect), or it is not possible to be precise about the location of an observation, in which case an observation might be stored as a line segment rather than a point.

Best regards,

Jason