Workshop D: Delineating
In this lab we'll extend our practice with raster analysis. After we get comfortable with the bathymetric and vessel traffic data, we'll create "categorical" rasters that describe a myriad of conditions that might help us locate groundfish habitat.
Here is our workflow:
Download bathymetric data, vessel traffic data, and create a proximity raster. Or download all data here.
Create subjective nominal rasters that "categorize" habitats.
Combine rasters to create conditional values.
Make a map that shows the best places to look for groundfish.
Where do we find good bathymetric data for our recreational fishing grounds map?
Vessel Traffic Data
Vessel traffic density has many possible definitions. We'll use the traffic counts for 2010 so we can work with raw numbers.
In this example, we're trying to create a raster that represents -distance from mainland- -- how do we do that when our only way of designating mainland is in a vector dataset?
In preparation for our conditional addition, we classify our vessel count raster into -crowded- and -sparse- categories in our search for ideal groundfishing recreational areas.
Ideal Proximity and Depth
The two other criteria in this example (how near to the mainland, and how deep) need to be classified from their source data rasters. Here we establish the zones in preparation for conditional addition.
In order to isolate unique classes for these combined sets of criteria we use the raster calculator and add them together.
In this video we create a basic bathymetric-topographic basemap and put our new information on top of that. But how do we appropriately generalize layers of different levels of detail so they look more cohesive on the page? We deal with that too.