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Using TQL for more specific queries

I am trying to calculate the total area of roofs which are flat (i.e. with sloping roof height of 0). So far, in TQL I input the following:
This returns a number which I assume is the lot size of all buildings which have attibute/detail of slanting roof height. Is it possible to somehow specify this query further so I can input a certain number (to extract the lot size of all roofs with value of 0).
Thanks in advance :)


  • Hi Ellie,

    Yes, that is possible. You can make a TQL query more specific by adding more clauses to the query: in the query tool you can click on add clause to add an AND statement to your query.

    For your question, there are multiple ways to do this.
    Maybe it is the easiest to understand how it works by creating an Average overlay first in where you show the Slanting roof height attribute of the Buildings layer. Then create a new legend to see better what the flat roofs are. Make sure the gridsize of this overlay is small, so the result is more precise.
    Then in the query tool you can do the following query:
    SELECT_LOTSIZE_WHERE_GRID_IS_5_AND_MAXGRIDVALUE_IS_0.1 (where Grid_is_5 is the id of my Average overlay, the number could be different in your project). Now you have the lotsize of all the constructions that have a slanting roof height value of max 0.1.
    However, keep in mind that trees, parks, parking spaces, roads etc are also constructions. You probably do want to substract these lotsizes from the result of the query above. One example query to get the lotsize for the roads is then: SELECT_LOTSIZE_WHERE_GRID_IS_5_AND_MAXGRIDVALUE_IS_0.1_AND_CATEGORY_IS_ROAD
    It is probably the easiest to do these calculations in an ( file in where you can put these different category queries in cells next to each other and substract them from the total flat roof lotsize.

    I hope my answer is helpful to you!

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    Tygron support team

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