I am attempting to create an Accessibility surface for the entire state of Florida. I have created a 6X6 mile grid of points over the state (from the create fishnet tool). For each grid centroid I created a 6 mile service area using Network Analyst. I also have extracted shopping opportunities from the statewide parcel dataset. For each six mile service area, I want to calculate an OD cost matrix from the grid point from which the service area was created to the shopping parcels whose centroids fall within the particular service area. I will then use an accessibility equation to calculate an accessibility value for each grid point based on the 6 mile serve area and interpolate over those values to create a continuous surface.
I have a decent amount of model builder experience and some python. In my head I know what I have to do (I believe). I must loop through the service area feature class one by one, select the parcels whose centroids fall within the particular service area and create the OD matrix from that selection. Is this possible? If so can I do this in model builder or will Python be a more appropriate avenue? I think if I am pointed in the right direction I can it done. Thanks so much. Let me know if you need any more clarification.
Russell Provost Master's Student/Research Assistant Department of Regional and Urban Planning/GeoPlan Center College of Design, Construction, and Planning University of Florida
If the goal is to compute distances from each grid centroid to eveything within 6 miles then there is no need to first create service areas to select them. Create an OD layer and first load your centroids as Origins and then all the points as destinations and then set a 6 mile cutoff on the OD layer properties and solve. In fact since the 6 mile cutoff is there, turn off Hierarchy and it will solve very quickly. The output Lines table will have distances from all centroids to points within 6 miles (their may be overlaps...)
Another hint, depending on what kind of "accessibility" numbers you need..look at Location-Allocation with the Maximize Market Share model. Set your centroids as Facilities with the REQUIRED status, load your points as demand points and then you can choose the maximize market share, set a cutoff of 6 miles, chose a power or exponential decay and set an exponent and solve for all required facilties. It will have computed spatial interactions between all pairs...of course this may not be what you need.