Inspired by the hypnotically simple but elegant wind map we challenged ourselves with building a conceptually similar app based on USGS stream gauge data.
Click here to access the live application.
Click here to download the source code.
The hydrographic network used and shown lightly in the background is derived from the World Hydro Reference Overlay. To improve display performance the dataset was thinned of minor rivers and generalized. To assist with client-side animation, rivers were dissolved to multi-part polylines using river names as the aggregate.
Stream gauge locations and flow data for the month of June 2012 were downloaded from the USGS. Considerable manual editing was required to when gauges to stream associations were not obvious or ambiguous. Once associated, stream flow volumes were distributed along the hydrographic network. Of the 9,000+ USGS stream gauges, only 2,000 were used.
The hydrographic network and the flow data were published to an ArcGIS Server as map services.
The client application consists of a Silverlight based web app. Silverlight was chosen merely because of the availability of technical expertise. The animating “flares” consist of a collection of paths on a canvas overlay. Each path is geometrically described by a quadratic bezier curve with control points that animate over time. For performance reasons we chose to display and animate these flares independent of the map, that is, not map graphics. Flares and the associated animations are recreated every time the map is panned or zoomed.
This app displays average daily flow for the month of June 2012. Our intention in a future release is to show average daily flow every week or month.
Contributed by Witold F. and Richie C.