Avin's Blog

Adventures in programming and data.

  • Querying ArcGIS attribute subtypes and domains with SQL

    ArcGIS geodatabases have the concept of domains, where an attribute can be restricted to a set of values, similar to a drop down list. Furthermore, geodatabases also allow an attribute to be specified as a subtype where the subtype determines which set of domains that apply to attributes. This can be used when setting up […]

  • web.config for React and Node.js on Azure App Service

    I’ve been creating a web application using React and Node.js, and decided to host it on Azure App Service. I had a lot of difficulty finding an appropriate web.config rewrite rules that would host static assets, redirect deep React Router links to index.html and send API calls to Node.js via iisnode. I finally came across […]

  • WebdriverIO with ChromeDriver headless without Selenium

    I was excited to discover that WebdriverIO supports the use of ChromeDriver running in headless mode without the use of Selenium (because ChromeDriver supports the WebDriver protocol). Here’s a starter guide (assuming Node.js is installed): Install Chrome Web Browser Download ChromeDriver Run ChromeDriver Install WebdriverIO by running npm i webdriverio Run the following file (based […]

  • Multiple layouts with React Router v4

    I was searching for a way to add use multiple layouts with React Router v4. I could only find examples for v3, but was inspired by the Redirects (Auth) example in the docs. I created a simple wrapper component for a Route that allows a layout prop to be passed which renders the component as […]

  • Creating a ArcGIS map service raster layer in PyQGIS

    It’s relatively straightforward creating layers programatically in QGIS using PyQGIS. However, the documentation isn’t clear on how to use create a raster layer from a ArcGIS map service. The list of raster providers can be found by searching for addRasterProviderDialog in qgsdatasourcemanagerdialog.cpp. There are two mandatory parts to the data source string when specifying the […]

  • ASX 200 Market Cap

    I recently came across this /r/dataisbeautiful post and was wondering what the equivalent would look like using Australian stocks. I found historical market cap data for the ASX 200 and using D3 created a similar visualisation, experimenting with D3’s transitions, scales, areas and axis. Source code on GitHub.

  • Websockets are easy

    I was interested in getting a minimal example working for Websockets and it was surprisingly easy to get a demo working between Node.js and a browser. First install the ws library: Create an index.js file with the contents: Start the Node.js process: In a browser console, send a message to the Node.js process:

  • Re-rendering map layers

    I recently was optimising the performance of a Leaflet-based map that rendered TopoJSON layers via Omnivore. The layers were a visualisation using the ABS’s Postal Areas, and while there was only a single TopoJSON file, this resulted in a number of feature layers being displayed, with each bound to their own data. The data for […]

  • Templated SQL

    I’ve recently been working on a data migration SQL script that performs the same operations against numerous tables. While I could use dynamic SQL – where SQL statements are built as a string and then executed – I don’t particularly like the downsides: It cannot be checked at compile time It is difficult to read, […]

  • Leaflet and Google Maps

    I’ve recently been developing an application that uses Leaflet to interactivity with a geographic map. One of the business requirements was to use Google Maps as a basemap, since it is pervasively used by our customers. A naive implementation used Leaflet’s tileLayer to render the tiles directly: This approach, while simple, does not conform to […]