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  • Apr 2014

    Dynamic Holland Shading

    Dynamic Holland Shading

    Dynamic Holland Shading

    The National Height Model of the Netherlands (AHN) which has now been released enables the height differences in the Netherlands to be identified very precisely. Using the very latest web technologies, we have created a dynamic ‘hill-shading’ map, which depending on the time and the day, shows the position of the sun using shadows.

    By releasing the National Height Model of the Netherlands (AHN), the government wants to encourage the reuse of this data. The data are measured to help to manage the water in the Netherlands. However, the accuracy and the complete coverage of this data also means that it is attractive for all sorts of other uses, such as the dynamic ‘hill-shading’ map. This enables you to see which areas receive more or less sun based on the time of the day and the day in the year.

    What is it?

    The Dynamic Holland Shading uses techniques that are comparable to the AHN-viewer (in Dutch). By dividing the height data into small tiles and encrypting these in a particular way, the browser is able to calculate the gradient and direction. The angle of the sun is determined based on the day and the time. Then, using Web Workers a calculation is made in the background to work out the light intensity in that location (‘shadow’).

    Unique attributes

    The AHN is a very large data set which requires powerful computers to work with. By serving the data in small tiles to the browser, only the data being looked at by the user has to be processed. This enables dynamic visualisations to also be created, such as a hill-shading based on the time and date, but also dynamic classification of the height in order to properly map out small height differences.

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