This story map accompanies the Esri spatial analysis case study "Where are the best locations for a golf resort?" In the case study, a team of market analysts uses a story map such as this one to present their analysis to management and investors. (By the way, the case study includes a workflow and data so you can recreate the analysis.) While this fictional story is about siting a golf resort, the method--weighted raster overlay--can be applied to a wide range of projects.
Our goal was to identify seven potential sites for the proposed golf resort, each 1500 acres in size, to provide options for the development team to consider. The team have narrowed the search area to two counties, with a third adjacent county as a backup option.
The team also specified the criteria for a suitable site. Our analysis consisted of creating a map layer representing each criterion and assigning suitability scores to the values on each layer (for this initial set of steps we included the entire region, as you'll see). The scored layers were assigned weights, combined, and clipped to the two preferred counties to create a map showing areas having higher and lower scores. The final step was to identify the seven most suitable sites.
The development team identified six criteria that, at a minimum, would make a location suitable as a site for the resort.
Gentle slopes
Certain land cover types
Near (but not too near) an airport
Near a river
A view of mountain peaks
Surrounded by a variety of landscapes
We created the slope layer from an elevation layer. Slopes within the region range from about 60 degrees to 0 degrees (flat).
We then assigned scores to the slope values, from 5 (flattest, and most suitable), to 1 (steepest, and least suitable).
Slopes greater than 30 degrees were excluded (they appear as dark gray flecks on the map).
The predominant land cover in the region includes evergreen forest, scrub, and agricultural crops.
We assigned suitability scores to land cover types based on how easy they are to build on and/or how aesthetically pleasing they are.
The areas in gray are deemed not at all suitable. They include wetlands and open water, perennial snow and ice, and developed areas.
We selected public use airports within 50 miles of the county borders and created drive time rings in 5-minute increments.
At this stage we used a 60-minute cut-off, knowing the maximum travel time for suitable locations would be less than this.
After consulting with the marketing team, we assigned suitability values to drive time ranges.
Locations less than 5 minutes or greater than 35 minutes from an airport were deemed not suitable (gray areas).
To start, we created a layer showing how far each location is from a river.
We then assigned a high suitability value to areas within a mile of a river and a medium value to areas between one and two miles from a river. All other areas were assigned a low suitability value.
Using peaks over 3000 meters elevation, we created a viewshed surface showing areas that have a view of at least one of those peaks.
We assigned a high suitability value to the areas with a view of at least one peak. Areas without a view of mountain peaks are not excluded, but rather assigned a low suitability value.
We started by generalizing land cover into five categories, or landscape types.
Areas in gray represent landscape types deemed less aesthetically pleasing, such as developed areas, barren lands, and snow and ice. These were excluded.
We used the GIS to calculate the number of different landscape types within a quarter-mile of each location (one-acre square). We then assigned each location a suitability value corresponding to the number of surrounding types.
We are about to reveal that. First, though we thought you might want to know how we got from the maps showing suitability scores for the six criteria to identifying the most suitable locations.
Basically, we added the six maps together (we could do this since the maps all use the same scale, from 5 to 1). Here they are again, all in one place. Dark green areas are more suitable, yellow areas less. Areas in gray are considered not suitable at all.
When we added the layers we gave a higher weight to slope (a weight of 3) since it's really important to have gentle slopes for the golf courses. We also gave a weight of 2 to land cover and distance from airports as these were considered somewhat important factors. The other three criteria were not given additional weight.
But that's not all. Since the resort cannot be built on public land, we included a layer of privately-owned land to ensure suitable locations are confined to these areas.
And, we limited potential sites to the two preferred counties.
A map showing all the suitable areas, ranging from green for more suitable, through yellow, to red for less suitable.
All other areas are considered not suitable for one reason or another--they are on public land, are too far from an airport, are already developed, or otherwise deemed not good locations for the resort.
From the suitability map emerge the seven most suitable locations. To create these, the GIS essentially scanned through the suitability map and defined sites that are 1500 acres in size and have the overall highest suitability scores.
The sites are ranked relative to each other from the most suitable--yes, green--to least suitable, red. The differences between the sites, in terms of overall suitability scores, is very small--any of these sites would be a good location for the resort.
Also, these are not final configurations for the resort property--only a starting point. Other factors such as existing parcel boundaries and engineering constraints will dictate the final site boundaries.
The next step is to take a closer look at each of the sites. For a start, here are simulated aerial views of the two areas where the sites are located. The sites to the west are mainly located on shrub and grassland, but are near forests and a major river, with a view of a major peak. The sites to the east are located near agricultural land, and are near highways (red lines) and a river.
We'll also use GIS to compare the sites, looking at the total acreage of flat slopes, the amount of each land cover type, and distance from an airport. With the approval of management, the acquisitions team will start researching property ownership and valuations. The design team will follow with site visits.
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