Many of you know about JSON, an object serialization scheme that has rapidly gained acceptance in AJAX-style applications. What you may not know is that there is an effort to standardise the representation of JSON-ified spatial features, known as GeoJSON.
FME is usually quick to support new formats (like KML and GeoRSS) but this time Safe has surpassed themselves, getting early JSON and GeoJSON support into their betas before the GeoJSON specification has reached a release version. Tonight I took some time out to play with this new support.
The basis of JSON support in FME is provided by two new read/write formats: JSON and GeoJSON. These new formats are augmented by two new transformers: JSONExploder and JSONExtractor. To get started, I’m going to show you how to extract data from a JSON source I happen to have lying around (it’s publicly available at Yahoo Pipes), which looks like this:
When you first import this data source into FME, it is imported with the top level of attributes broken out. In this case, Pipes returns a top-level object with several attributes (link, description, etc) that you can see in my test workspace below:
Now, this isn’t much use, because my features are hidden inside the “items” attribute. In order to get them out, I first need to explode my single object into multiple features. The new JSONExploder transformer comes to the rescue here:
Now, I have a unique feature for each of my feed items, but I really want some of the nested attributes. In particular, I want the description from the root of the item, and the nested y:location["lat"] and y:location["lon"] attributes. The JSONExtractor makes it easy to pull these out into new attributes:
And once adding a couple more of these, each of my features has some nice attributes attached to it, which I could then turn into points if I wanted:
OK, so that’s kinda cool from a straight ETL standpoint. I can take in JSON, mess with it, and then pump it out into whatever format I want. But the fun stuff is when you start getting into GeoJSON. Fortunately there are a couple early adopters, Christopher Schmidt and Howard Butler, who gave me some feeds to play around with. The first of these comes from Christopher’s super-flexible FeatureServer application (check it out, it’s open source):
The features displayed on this OpenLayers map can be easily downloaded from FeatureServer in GeoJSON format (or KML, or GeoRSS, or whatever). The URL for the GeoJSON representation is:
Pulling this into FME is as simple as creating a new FME data source, and specifying the URL:
As you can see, you can then treat this data like any other spatial data source:
Now, for a final example… Howard has a GeoJSON resource collection of counties in Iowa, accessible in a pattern something like this:
Now we could take this feature, in its source projection of UTM Zone 15N NAD83, but Howard’s put together a really nifty (non-commercial use only, unless you want to pay Howard some $$$) JSON-based web processing projection service. Not only that, but he’s also made it smart enough to interpret projections referenced locally, but also from the oh-so-cool (and built as a collaborative effort between Christopher and Howard) SpatialReference.org. So, all you need to do is feed it the URL of your source data, the url of your source CRS (http://spatialreference.org/ref/epsg/26915/) and the url of your destination CRS (http://spatialreference.org/ref/epsg/4326/). Like so:
And, as just another link in the dynamic web chain, FME can read this transformed JSON feature:
Now, for desktop FME users, this gives us “Pipes on Steroids”: all the mashup flexibility of Yahoo Pipes, with the huge format support and rich processing model of FME. As cool as this is, I think the real power will be seen whenever Safe integrates this functionality into their Server product. It will allow them to play well on both the “enterprise” traditional GML/WFS/etc level and on the neogeography JSON/GeoRSS/KML mashup level with a single product from a single (or multiple if you want) data source. For organisations that want turn-key interoperability solutions, FME Server is going to rock your world.
P.S. I’m thinking about getting a personalized plate that says GEO JSN :)