Monday, 8 October 2012

Mapping New Zealand: Where are the hot and cold springs?

New Zealand has a large number of cold and hot springs, where water flows to the surface of the earth from underground. Where can you find these springs? This blog post will show you can visualise a spring point dataset on a Leaflet map. 

You can find spring point dataset at LINZ Data Service, which contains 147 significant springs either by size or location. I downloaded the dataset as a shapefile, and converted it to GeoJSON using ogr2ogr:

ogr2ogr -f "GeoJSON" -lco COORDINATE_PRECISION=4 nz-spring-points.json nz-spring-points-topo-150.shp 

The resulting GeoJSON FeatureCollection can be assigned to a JavaScript variable:

var springs = {"type":"FeatureCollection","features":[{...

... and visualised with Leaflet's GeoJSON layer and L.circleMarker:

Here is the result:

Fullscreen map

Te Waikoropupū Springs in Golden Bay, discharging 14,000 litres of water per second, - the largest freshwater springs in New Zealand.

The horizontal visibility of the water in the springs has been measured at an average of 63 metres, second only to sub-glacial water in the Antarctic.

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