Overview

The Union County GIS REST Web Services Framework allows spatial analysis to be performed on Union County GIS data layers through simple HTTP requests. Our Community Mapper application uses these services almost exclusively to perform spatial analysis and return relevant results to our users.

The following questions could all be answered using these services:

  • What are the parks nearest to a parcel with an account number of '09229092'? (see example below)
  • Which soils are located on my property?
  • Am I within 2 miles of a Voluntary Agricultural District?
  • I live at 1306 Buckthorne Ct. What Volunteer Fire District responds in an emergency?
  • Which FEMA Flood Zone Map Panel(s) is/are my property on?
  • Is my property within a Water Supply Watershed?

Example

Say we want to find parks within a specified distance of a particular parcel. We know our parcel "acctno" value (account number/parcel number) is 09229092 and that the layer we want to find features for is "parks." In this situation we would utilize the "Buffer Feature" service to find the names and coordinates of all the parks within 1500 feet of said parcel.

Request

    
    http://gisapps.co.union.nc.us/ws/rest/v2/geo_bufferfeature.ashx?    -- Service end-point
    from_geotable=parcels&                                              -- Buffer features from the "parcels" layer
    to_geotable=parks&                                                  -- Return features from the "parks" layer
    fields=t.park_name,x(t.the_geom),y(t.the_geom)&                     -- Return "park_name" and the x/y coordinates from parks
    parameters=f.acctno='09229092'&                                     -- Only buffer parcels with acctno value of '09229092'
    distance=1500&                                                      -- Buffer the feature(s) by 1500 feet
    limit=&                                                             -- We could limit our results here
    format=json                                                         -- Return data in JSON format (XML also available)
    

Response

    
    {rows:[
      {park_name:"Belk Tonawanda Park",x:"1535499.39765981",y:"453780.840915829",distance:"687.614708940814"},
      {park_name:"Don Griffin Park",x:"1536707.85465981",y:"455051.135715827",distance:"1306.18428332238"}
    ]}
    
    

Below is a visual representation of the above Buffer Feature request.

Parcel/Parks Buffer Example

How It Works

Simply put, this collection of services dynamically creates and executes spatial queries against a PostGIS database (spatially enabled database). Analysis results depend entirely on user input and response format preference.