[Qgis-user] How to get the thickness of a geol. layer from elevation isoline features

[Stefan Giese (WhereGroup)]

Hi Eva,

welcome to the list. You asked a plenty of questions, so it would be
easier to start with some links on the web:

  * Stackoverflow discussion on that:
    https://gis.stackexchange.com/questions/60228/generating-dem-from-contour-shapefile-using-qgis
  * a GRASS Tutorial: https://grasswiki.osgeo.org/wiki/Contour_lines_to_DEM
  * and a short youtube tutorial:
    https://www.youtube.com/watch?v=PhJ77uHlTJA

Hope this helps

Stefan

Am 03.11.2020 um 14:39 schrieb fantypus at web.de:
>
> Hi all,
>
> I have the following task:
>
> I need to create a map with contour lines showing the thickness of one
> geological layer/horizon (actually not the true thickness, but the
> vertical extent is required, so if you drill down at one point, what
> is the distance between the upper and lower edge of the horizon).
>
> The only data I have are two line features (shape files) of isolines
> with elevation values (in m NHN) of each the upper edge and lower edge
> of the horizon.
>
> My approach would be something like this, but I can’t figure out how
> exactly to do it:
>
>   * Create a raster from each line feature (did that, but only the
>     lines are rastered, so would need a polygon to get a plane? How do
>     that? How can I include the elevation values of the lines into the
>     polygon?)
>   * Interpolate the elevation values inbetween the isolines to receive
>     a plane of elevation values (in my opinion would need a polygon to
>     get a plane, but for interpolation input Points are needed? And
>     which interpolation method? Also, some of the isolines are offset
>     by faults, so need sharp edges in these areas, how to integrate
>     that in the interpolation?)
>   * Then calculate the vertical distance at each point in the area
>     between the two planes to get the thickness (how, which tool does
>     that?)
>   * Create a raster showing the thickness throughout the area in
>     colour range
>   * Add contour lines showing the thickness of the horizon
>
> Maybe there is even a better and probably much simpler way to do this.
> However, I am only a beginner in QGIS, python and statistics. So any
> help and easy to understand tips will be very much appreciated. I am
> using QGIS 3.10.11 by the way.
>
> Best regards,
>
> Eva
>
>
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