Your best bet is to look through the respective companies' websites and see if they offer some kind of API access to their data. These sites all pull from central real estate listing systems, so you may also want to look around to see if there is a state-based real estate listing service you can access directly, rather than go through a middle-man.
Whether or not this kind of data access is available, as well as what format the output data is in, will dictate the methods available to you to perform the kind of cross-checking you have in mind.
One potential method:
- Get parcel data from whatever local authority has it.
- Intersect parcels with areas of interest (wetlands, etc)
- Export a list of parcel numbers from the intersection
- Check new listings against a separate list (maybe a CSV or TXT file) based on parcel numbers.
That way, even if the data provider does not have spatial outputs like parcel shapes, you'll still be able to reliably identify any new listings that fall within these zones.
Not knowing the specifics of how the output data will look, it's hard to give a more concrete example. But I think this is certainly possible. After all, Zillow and others get their data from somewhere, so the same should be possible for you. Mind you, it may not be free...
- Josh Carlson
Kendall County GIS
