How to...

How-to

Terra Antiqua is designed with a particular workflow in mind (see Workflow Summary) oriented towards a full reconstruction from present-day geography to a global map of past geography. However, it is possible (and likely) that some users want to perform simple tasks on their (paleo)DEMs without going through the whole process. Each tool may be used separately (even the primary tools). They are independent algorithms perfectly functional on their own.

The table below summarizes some cases for those users who do not wish / need to follow said workflow, practically serving as a list of “shortcuts” through this manual. It is meant to evolve and grow as it is used, so your feedback and comments are most welcome. Although we are orienting this manual towards somewhat inexperienced QGIS users, some tasks must still be done using basic QGIS functionality or other QGIS plugins (Terra Antiqua can’t do everything!). These are duly referenced in the corresponding line.

How to... Tools needed What you need to do Step by step
Use only certain areas of a raster for the compilation. Compile Topo-/Bathymetry
Copy/Paste Raster
You have to do the compilation using the whole map extent.

Then you can use the tool Copy/Paste Raster to copy those areas from the original raster into the compiled one.
  1. Follow the step-by-step indications to use Compile Topo- / Bathymetry Icon for Compile Topo/Bathymetry.
  2. Once the compilation is done and you have saved the output raster, use Copy/Paste Raster Icon for Standard Processing Tools with following parameters:
    • Raster to be modified: The Compiled DEM you obtained as output of Compile Topo- / Bathymetry
    • Raster you want to copy values from: The original raster where you want to take some regions from.
    • Mask layer: A shapefile with masks for the areas you want to take.
Visualize a map in 3D External plugin: Qgis2threejs
  1. Download the plugin Qgis2threejs from the QGIS repository
  2. Screenshot_QGIS_plugin repository
  3. Open the plugin and select a raster layer on the map canvas
Plot data in QGIS
Main QGIS function This is a core function of QGIS Chapters 13, 14 and 15 of the QGIS manual deal with that.
Create shapefiles, draw polygons, lines, or points Main QGIS function This is a core function of QGIS Chapters 13, 14 and 15 of the QGIS manual deal with that.
Quickly interpolate over a small region Remove Artefacts Remove Artefacts allows you to spontaneously draw one or more polygons and interpolate over those areas. Click on the icon Icon remove artefacts and follow the step-by-step indications of the tool Remove Artefacts.
In the parameters, you need to define the elevation values you want to remove so that the algorithm interpolates the values for those pixels.
Change the shorelines of a map Set Paleoshorelines Run the tool Set Paleoshorelines using, as input raster, the DEM you want to change the shorelines of. You need a shapefile with a set of polygons to define the new shorelines. Prepare your shapefile with the masks (polygons) of the right paleoshorelines.
Remember: The edge of the polygon is the shoreline. The area inside the polygon will be emerged and the area outside submerged.
Click on the icon Icon set paleoshorelines and follow the step-by-step instructions of the tool Set Paleoshorelines.
Work on the reconstruction of a smaller region instead of the entire world All tools can be used normally, only the area of interest should be cut and used as the entire area The only difference is that you have to export your map to a smaller extent after using Compile Topo-/Bathymetry and Set Paleoshorelines.
  1. Use all tools of Terra Antiqua normally in the full extent of the map as described in this manual.
  2. Once the reconstruction is done, right-click on the final raster, choose Export > Save as...
  3. In the Export window, select the extent of your area of interest, file name, and location to save the new raster. Then hit OK.
  4. You can then keep working on the new raster, which has been "cut" from the full extent.
Make a future map All tools in Terra Antiqua are suitable for working on a map of the future earth.

Technically, there is no limitation for the time of reconstruction (always to be specified in million years). The most useful tools for a reconstruction in the future, however, are Set Paleoshorelines Icon set paleoshorelines, Modify Topo- / Bathymetry Icon Modify TB, Create Topo- / Bathymetry Icon Create TB, Remove Artefacts Icon remove artefacts, Smoothing Icon standard processing tools, Fill Gaps Icon standard processing tools, and Isostatic Compensation Icon standard processing tools. Please follow the step-by-step indications in those pages and keep in mind, in this case, the original geography (present-day) is older than the reconstructed one (future geography).

Depending on how distant the future map is, you may need to rotate the tectonic blocks in GPlates. If you have a rotation model for the future and want to use it, please refer to GPlates manual and the section of this manual on Preliminary Steps to use it to prepare your input data.


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