[GPlates-discuss] See which features constitute a topology

[John Cannon]

Hi Thomas,

The quick answer is to turn on "View > Geometry Visibility > Show Topological Sections".


There's a new setting "View > Geometry Visibility > Show Topological Sections" show/hide the dangling bits of topologies. This setting is turned off by default, so that users new to GPlates don't get confused by these dangling bits - because they're expecting a continuously closing boundary around each plate (without the intersecting bits). In other words, a new user can load up a rotation file and some dynamic polygon files, and only see the topologies (without the intersecting line geometries they were derived from).

For advanced users, you will want to check that box so that topological sections are visible. Note that this setting is saved as part of a project, so if you receive a project from someone else that has this box checked then you won't need to check it after you load their project. Also you can have it always checked by default at GPlates startup by checking the "Show topological sections" box in the "Edit > Preferences > View" dialog. However note that if you subsequently load a project, or a session, it will override your default for as long as that project/session is loaded (eg, until you "clear session").


I should mention that it's also possible to simply make the green layers invisible (in the layers dialog) to hide the dangling bits, but that does not always work. For example, if you have a topological line (that is used as part of a topological plate boundary) then it will be in a purple layer (because it's 'topological'), and making that layer invisible (because you want to hide the topological line because it's a dangling bit) will also hide any plate boundary topologies that happen to be in the same layer/file. Also users new to GPlates are not always aware that they would need to hide layers like this. Hence the default of not showing these geometries by default (regardless of whether the layer is visible or not).

Note that only those geometries that are actually used by topologies are hidden (by the "View > Geometry Visibility > Show Topological Sections" setting). So in your case some geometries are hidden and some are not. The ones that are not hidden are not being used by any loaded topologies (GPlates automatically scans all loaded topological rigid and deforming boundaries). This is why you could click on some but not others. And once you enable the setting you should be able to click on these features both normally and when using Topology Boundary Sections In the Edit Topology Sections tool.


Since it's related to this  discussion, there's a pyGPlates script to remove any features not directly or indirectly referenced by topological rigid and deforming boundaries. This can be used by those who provide topological data (we have started using it). It is a post-process to be used just before releasing a topological model. It essentially finds all features not referenced by topological rigid/deforming boundaries and removes them from the dataset, so that when users load the dataset the "View > Geometry Visibility > Show Topological Sections" setting works properly...
https://protect-au.mimecast.com/s/9Qy7C4QZ1RFBJQYExTOcjtX?domain=github.com  (use the "--help"  option to see a description of the command-line arguments)

Regards,
John

From: GPlates-discuss <gplates-discuss-bounces at mailman.sydney.edu.au> On Behalf Of Linden, T.J.M. van der (Thomas)
Sent: Saturday, 29 February 2020 2:01 AM
To: gplates-discuss at mailman.sydney.edu.au
Subject: [GPlates-discuss] See which features constitute a topology

Hi,

I have been trying to find which features constitute topologies in a downloaded GPlates model (in this case Matthews et al. GPC 2016, available from https://protect-au.mimecast.com/s/kKm2C5QZ29FZ0Qg31cOABso?domain=doi.org<https://protect-au.mimecast.com/s/kKm2C5QZ29FZ0Qg31cOABso?domain=doi.org>). I would like to know which parts of the topology are subduction zone, mid ocean ridge or passive margin. So far my efforts were not successful.

Methods tried:

  *   Select the topology and delete it, this results in the deletion of all features constituting the topology.
  *   Disabling or deleting the layer with topologies
  *   Selecting the topology and look in Query feature

What works for some features is to select the Topology and then click on individual features constituting the topology. However not all features react to clicking in this mode (for instance the subduction zone of the Andes does not).
Also the list shown in Topology Boundary Sections, cannot be used to highlight individual features on the map.

Does anyone know a solution?

I can imagine writing a pyGPlates script to create a new file with only features, but would like to have a direct graphical method.

I use GPlates 2.2.0 in Windows10.

Cheers from Berlin,
Thomas

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