Re: RE: Model not locating development projects

Thanks Paul,

I am using a more recent version of the code with the
development_constraints table containing min and max fields for the general
landuse types. I did as you suggested (built a rough development constraints
table and re-estimated) and am getting similar results. Commercial
development is getting located but industrial sqft and residential units are
not, or not as much as they should be. Residential development is being
located at about 1 unit per year and industrial development is not being
located at all...

I have attached a log files for two of the years.
   
I'm a bit baffled by this. Do you have any other suggestions as to why this
is happening?
 
Thanks,

Quinn Korbulic
GIS Coordinator
Spatial Applications and Research Center
New Mexico State University
Geography Department
Box 30001, Dept. MAP
Las Cruces, NM 88003-0001
VOICE (505) 646-5755
FAX (505) 646-7430

Quinn

First, I am assuming you are using fairly recent code and that the
development_constraints table contains max_residential_units and similar
fields rather than the earlier format that did not contain min and max
fields, and instead had a development_type field. If this is not the case,
please indicate what version of the model system you are using.

I think the problem is due to a change in the behavior of the model when the
development constraints are not specified in the table. In the transition
style developer model (the earlier model that would have used the
development constraints table that included a development_type field in it),
leaving out constraints information behaved as you expected: no constraints
meant that a cell could transition to any of the development types. There
were other issues with this transition model, but that is not the issue so
let's put that aside. The newer developer model that uses a location choice
framework handles development constraints somewhat differently. Most
importantly in your case, it uses a capacity calculation to figure out if a
project of a given size can fit into a cell, given its available developable
capacity --- which is determined by looking up the constraints that apply to
the cell and computing whether the remaining capacity is greater than the
size of the project to be placed. That works as you expect in most cases,
but not if you do not specify any constraint information at all. In that
case, it is treated as having no capacity rather than infinite capacity. I
hope that helps explain why it is behaving as it is. Now on to what to do
about it.

If you really want to see what would happen if you had no planning
constraints at all, you could put in a single development constraint record
with a -1 for the plan_type_id and a fairly high value for the
max_residential_units, max_commercial_sqft, max_industrial_sqft. I don't
think this would be very effective for estimating the model parameters,
since this is not how the world generally works. You will get better results
by estimating the model using even a rough approximation of what the
constraints actually are in local land use policy, and putting this into the
development_constraints table.

Hope this helps.

Paul