Friday, October 16, 2015

GIS in the Browser


Dropchop is a browser based GIS built with Mapbox and Turf.js. It allows you to perform quite sophisticated spatial queries on mapped data without a server and in your choice of internet browser.

Dropchop allows you to upload data from your computer, from a URL or even from Overpass Turbo (OpenStreetMap POI's etc) and to perform quite sophisticated spatial queries. The best way to find out what is possible with Dropchop is to play with it. If you don't have any map data to hand then you can use the in-built Overpass Turbo wizard to grab some data from OpenStreetMap.

For example you could use the Overpass Turbo option (using the menu to left of the screen) to upload all the bars mapped on OpenStreetMap in the current map view. This is very simple as 'bars' is the default setting in the in-built Overpass Turbo wizard.

Once all the bars have loaded on the map you can then perform a number of spatial queries on your bar data. All the queries that are possible are highlighted in the map sidebar. The screenshot above shows bars in East London with a buffer of 5 miles around all the mapped bars. Loading the bar data and performing the buffer took me about 20 seconds.

Once you have performed the required GIS operations on your mapped data you can download the results as a GeoJSON file or as a shapefile.
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