{"id":3973,"date":"2019-11-13T00:16:12","date_gmt":"2019-11-13T00:16:12","guid":{"rendered":"https:\/\/dalelane.co.uk\/blog\/?p=3973"},"modified":"2019-11-13T00:26:27","modified_gmt":"2019-11-13T00:26:27","slug":"geo-spatial-data-in-scratch","status":"publish","type":"post","link":"https:\/\/dalelane.co.uk\/blog\/?p=3973","title":{"rendered":"Geo-spatial data in Scratch"},"content":{"rendered":"

In this post, I want to share a random thing I made in Scratch this week, and ask for suggestions of what I could do with it.<\/strong><\/p>\n

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\nClick for larger version<\/em><\/small><\/a><\/p>\n

I get a lot of emails from teachers and coding groups asking for help with Scratch<\/a> projects. They’re normally small or specific questions – asking for help figuring out a bug in a Scratch project or how to get something working.<\/p>\n

But this week I got a more challenging email. It asked for a way to show a map in Scratch, and use a Scratch script to plot points on the map, given coordinates in latitude and longitude<\/strong>.<\/p>\n

I agreed to give it a try. (Details for how to access it below.)<\/p>\n

It was harder than I expected to get it working.<\/p>\n

There were two main challenges.<\/p>\n

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  1. \nThe code I wanted to write was more complicated than I could express with Scratch blocks.<\/strong><\/p>\n

    So I cheated, wrote it in JavaScript<\/a>, and put it in an extension. (That meant the code I wrote in JavaScript was represented as a couple of new blocks in the Scratch palette, that I could just use as-is).<\/p>\n

    I’m sure it could be done in Scratch, but I didn’t have the time to figure it out – this was just a thousand times quicker for me.<\/em><\/li>\n

  2. \nTurning latitude and longitude coordinates from a not-flat Earth into 2D coordinates for a very-flat screen is a pain.<\/strong><\/p>\n

    I know I’m stating the obvious, but map projections are hard. I’m sure my implementation<\/a> would make any cartographer shudder, but I only needed it to roughly work (the Scratch canvas coordinate system is only 480×360<\/a> so precision was never going to be an option) and only for a relatively small area (they wanted it to work for a UK map, not a world map). I’d charitably describe it as a quick-and-dirty hack, but that was all I had time for.<\/li>\n<\/ol>\n

    I’ve put the whole thing on GitHub<\/a> in case it’s useful to anyone else.<\/p>\n

    If you know how to convert lat\/lon coordinates to a map x\/y coordinates properly, I’d welcome any fixes!<\/em><\/p>\n

    And if you’d like to give it a try:<\/strong><\/p>\n