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The CASA Blog Network

The latest outputs from researchers, alumni and friends at the UCL Centre for Advanced Spatial Analysis (CASA).

    The CASA Blog Network

    Category: SQL

    Map algebra with callbacks in PostGIS 2.1

    Posted on Sunday 21 July 2013 by george

    I’ve been playing with the much-enhanced raster support in PostGIS 2.1 in the last few days. Amongst other things I’ve been producing maps with ST_MapAlgebra, which has changed a little since 2.0. The example callback function in the documentation is somewhat unhelpfully bare-bones: it always returns 0, touching none of its arguments. So here’s an […]

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    GIS, PostGIS, SQL

    Map algebra with callbacks in PostGIS 2.1

    Posted on Sunday 21 July 2013 by george

    I’ve been playing with the much-enhanced raster support in PostGIS 2.1 in the last few days. Amongst other things I’ve been producing maps with ST_MapAlgebra, which has changed a little since 2.0. The example callback function in the documentation is somewhat unhelpfully bare-bones: it always returns 0, touching none of its arguments. So here’s an […]

    Continue reading »
    GIS, PostGIS, SQL

    Sunrise and sunset times with PostGIS and PL/R

    Posted on Monday 15 October 2012 by george

    Since light can affect happiness, two important pieces of environmental data I add to the Mappiness data set during analysis are: (1) whether a response was made in daylight; and (2) day length when and where the response was made. To derive these, I need the date, time and location of the response, and sunrise […]

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    GIS, PL/R, PostGIS, SQL

    Sunrise and sunset times with PostGIS and PL/R

    Posted on Monday 15 October 2012 by george

    Since light can affect happiness, two important pieces of environmental data I add to the Mappiness data set during analysis are: (1) whether a response was made in daylight; and (2) day length when and where the response was made. To derive these, I need the date, time and location of the response, and sunrise […]

    Continue reading »
    GIS, PL/R, PostGIS, SQL

    Approximating kernel-weighted proportions in PostGIS

    Posted on Tuesday 16 August 2011 by george

    Imagine you want compare various locations in terms of the availability of a certain type of environment, such as fresh water. You might want to use a measure of the proximity of that environment — such as the nearest neighbour distance. You might want to use a measure of the quantity of that environment in […]

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    GIS, PostGIS, SQL

    MySQL gem for Ruby 1.9.x on Snow Leopard or Lion (Mac OS X 10.6 or 10.7)

    Posted on Thursday 4 August 2011 by george

    Updated May 2012 for Lion The secret to getting the MySQL gem to install and function with Ruby 1.9.x on Snow Leopard or Lion is: Install MySQL using the 64-bit .DMG package installer from dev.mysql.com Install Ruby using RVM or (preferably) rbenv Add …

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    mac, Ruby, SQL, System admin

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    • Networking City Research blog on urban environment and citizen movements in complex networks
    • @emergentcity The personal blog-space of Gareth Simons -> architect | urbanist interested in performative simulation at the urban scale; space and flows as computational processes; information entropy & irreversibility; and the ‘edge of chaos’. Views are my own.
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    • DataShine Blog DataShine is an output of the ESRC BODMAS project which ran from 2013-2015 at UCL. To cite the project or websites, please use: Oliver O’Brien & James Cheshire (2016) Interactive mapping for large, open demographic data sets using familiar geographical fe
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    • Population Geography promoting population geography, supporting population geographers
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    • Quantitative Methods Research Group (QMRG) – Royal Geographical Society with IBG
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    • Simulacra Showcasing land use transport modelling, urban complexity and sustainability research from the Centre for Advanced Spatial Analysis, University College London
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