Elevation profile plot

[nyalldawson]

This PR implements a native elevation profile tool.

Currently supports:

• Vector, raster and mesh layers, based on the corresponding layer's elevation settings. (E.g. vector layer profiles will respect terrain clamping settings and extrusion heights). (Point cloud layers will be implemented following this PR)
• Drawing profile lines interactively using a map tool which supports snapping, tracing, stream digitizing and curves
• Interactive navigation of the plot canvas, using the standard QGIS pan/zoom shortcuts. E.g. middle mouse button = pan, hold space = pan, ctrl + space = zoom, ctrl + mouse wheel = fine zoom
• Plots can be exported to PDF (as high quality vector objects, ready for any post-processing in Inkscape etc) or image formats

Some demonstrations:

Setting the profile curve line using a map tool:

Peek.2022-03-31.16-27.mp4

The profile chart style for layers can be set in their corresponding layer properties - elevation tab:

(Fun fact -- because these are rendered using standard QGIS line symbols, you can go really overboard with your profile tool appearance, by using geometry generators, paint effects, etc...!

)

[3nids]

It looks like you are re-creating all the canvas/tools/mouseevent logic here.

Wouldn't it have been possible to re-use the existing classes but stripping down the CRS notion or splitting them apart to have base common classes?

[nyalldawson]

It looks like you are re-creating all the canvas/tools/mouseevent logic here.
Wouldn't it have been possible to re-use the existing classes but stripping down the CRS notion or splitting them apart to have base common classes?

@3nids and I discussed this offline, and the conclusion was that trying to keep a common base class between map canvas and the profile plot would result in more complex code/complex API in order to handle all the requirements of both canvases.

[nyalldawson]

Showcase time!

Setting the profile curve line using a map tool:

(Thanks to recent work by @3nids, it was dead-simple to allow the profile curve to take advantage of ALL the digitizing options, including snapping, curve digitizing, stream digitizing, cad dock, tracing, ....!)

Peek.2022-03-31.16-27.mp4

The line style for raster and mesh layers can be set in their corresponding layer properties - elevation tab:

(Fun fact -- because these are rendered using standard QGIS line symbols, you can go really overboard with your profile tool appearance, by using geometry generators, paint effects, etc...!

)

[github-actions]

@nyalldawson
This pull request has been tagged as requiring documentation.

A documentation ticket will be opened at https://github.com/qgis/QGIS-Documentation when this PR is merged.

Please update the description (not the comments) with helpful description and screenshot to help the work from documentors.
Also, any commit having [needs-doc] or [Needs Documentation] in will see its message pushed to the issue, so please be as verbose as you can.

Thank you!

[nyalldawson]

I personally think this PR is ready for merging now (at least as a first step!). Additional functionality can be added in follow up PRs.

[3nids]

I had a very very quick look, no objection!

[nicogodet]

In use, I notice a flickering of secondary tick at a certain zoom

Happens also on Y axis

[DelazJ]

I personally think this PR is ready for merging now (at least as a first step!).

@nyalldawson I see this PR is labeled for changelog and docs so can you update the first message, please? Thanks.

[nyalldawson]

@nicogodet

In use, I notice a flickering of secondary tick at a certain zoom

Thanks, that's fixed now

[nyalldawson]

@DelazJ

I see this PR is labeled for changelog and docs so can you update the first message, please? Thanks.

Done

[nyalldawson]

Unrelated test failure

[nicogodet]

I believe these next comments are features but I just wanted to give a little feedback of the use of this new AWESOME feature ! 😃

• When plotting a long profile (I'm talking about kilometers) over a DEM, it can take few tens of seconds to plot it. It's full resolution, which is nice, but most of the times, we don't need the full resolution. ProfileTool plugin has a nice feature to disable the full resolution and instead, the DEM is sampled over the profile curve (max 1000 points per segment). A similar feature would be nice for speeding up the plot.

• When using vector layer and in particular, point vector layer, ProfileTool layer allow the use of a search buffer around the profile curve with the visualisation of the buffer and projected points. This is more convenient than snapping the profile curve on each points.

• Could be useful to allow the use of an attribute for vector layer instead of Z value only.

• A legend on the plot (with possibility to enable/disable layer, direct access to symbology).

• A mouse tracker when mouse over the plot (Distance and Z values) and visualisation of the position of the mouse on the profile curve.

• An "Add selected layer to plot" button ? (instead of opening layer properties)

All these comments do not change the excellent work done.

[wonder-sk]

👏 👏 👏 Really great work!

[uclaros]

Fantastic work! A few thoughts:

• It feels weird that zooming with the zoom tool also changes the Y scale depending on the proportions of the dragged rectangle. I'd suggest to keep Y scale intact when drag-zooming and have a separate mechanism for modifying it.
• The more you zoom, the rendering gets slower, while blocking the main thread. Update: This only happens with the fancy cat trail line style with svgs.
• Which band is used in multiband rasters? It would be nice to have that selectable.
• Zooming in way too much can get you trapped within Qgs2DPlot::calculateOptimisedIntervals()

[nyalldawson]

@nicogodet

I believe these next comments are features but I just wanted to give a little feedback of the use of this new AWESOME feature ! smiley

Thanks, it's definitely valued feedback!

When plotting a long profile (I'm talking about kilometers) over a DEM, it can take few tens of seconds to plot it. It's full resolution, which is nice, but most of the times, we don't need the full resolution. ProfileTool plugin has a nice feature to disable the full resolution and instead, the DEM is sampled over the profile curve (max 1000 points per segment). A similar feature would be nice for speeding up the plot.

I'm planning on addressing this in a followup (when the point cloud profiling is added). But yes, I agree that the performance on large raster layers in currently sub par.

When using vector layer and in particular, point vector layer, ProfileTool layer allow the use of a search buffer around the profile curve with the visualisation of the buffer and projected points. This is more convenient than snapping the profile curve on each points.

That's supported in the new API, but I haven't yet exposed a means for the user to set the search tolerance yet. That'll be added in a follow up.

Could be useful to allow the use of an attribute for vector layer instead of Z value only.

Agreed -- I'd like to see field/expression based support for both the height and the extrusion values. I'll see if I can fit this in, but no promises.

A legend on the plot (with possibility to enable/disable layer, direct access to symbology).

I've no plans for this at the moment, but I'll keep it in mind for future work.

A mouse tracker when mouse over the plot (Distance and Z values) and visualisation of the position of the mouse on the profile curve.

That's planned as a follow up PR.

An "Add selected layer to plot" button ? (instead of opening layer properties)

Right now the tool is using the assumption that the user wants to see all their project elevation enabled layers on the same plot. I also think we'll need to revise this in future, but I'm not sure what the best way to expose this will be. I'm leaning toward showing a filtered, checkable layer list on the left of the plot showing only elevation enabled layers, allowing users to check and rearrange the plot layers. But I'm also concerned about the loss of plot area this would cost. Ideas welcome 😄

[nyalldawson]

@uclaros

It feels weird that zooming with the zoom tool also changes the Y scale depending on the proportions of the dragged rectangle. I'd suggest to keep Y scale intact when drag-zooming and have a separate mechanism for modifying it.

I've added a dedicated tool for x-axis zoom only now, and put the action for it before the standard zoom.

The more you zoom, the rendering gets slower, while blocking the main thread. Update: This only happens with the fancy cat trail line style with svgs.

I'll try to find time to move the rendering to a background thread in a follow up

Which band is used in multiband rasters? It would be nice to have that selectable.

I've just added support for selecting the band in the layer- elevation properties tab.

Zooming in way too much can get you trapped within Qgs2DPlot::calculateOptimisedIntervals()

Thanks, fixed

[nicogodet]

A legend on the plot (with possibility to enable/disable layer, direct access to symbology).

I've no plans for this at the moment, but I'll keep it in mind for future work.

An "Add selected layer to plot" button ? (instead of opening layer properties)

Right now the tool is using the assumption that the user wants to see all their project elevation enabled layers on the same plot. I also think we'll need to revise this in future, but I'm not sure what the best way to expose this will be. I'm leaning toward showing a filtered, checkable layer list on the left of the plot showing only elevation enabled layers, allowing users to check and rearrange the plot layers. But I'm also concerned about the loss of plot area this would cost. Ideas welcome 😄

I think these two could be the same.
What I was think for the legend is at least a reminder of which plot belongs to which layer.
Regarding the loss of space, as long as it is not as much as the plugin, I think we are fine 😄

• Possibility to export plots as table (clip board, csv, ...) for external use like in Excel
• Use an existing curve layer/feature in addition to the temporary maptool
• As I try to maintain the current ProfileTool plugin, I noticed people use DXF export

[github-actions]

@nyalldawson
A documentation ticket has been opened at qgis/QGIS-Documentation#7485
It is your responsibility to visit this ticket and add as much detail as possible for the documentation team to correctly document this change.
Thank you!

[nyalldawson]

@nicogodet

Could be useful to allow the use of an attribute for vector layer instead of Z value only.

Done in #48177

[nyalldawson]

@nicogodet

Use an existing curve layer/feature in addition to the temporary maptool

Done in #48179

[nyalldawson]

@nicogodet

A legend on the plot (with possibility to enable/disable layer, direct access to symbology).

Done in #48248

[Jean-Roc]

Hi nyall, are you planning to present an option to set a "same scale axis" like in ProfileTool ? We funded this feature in the plugin because the different x/y scales for the same unit of measure often were a source of misreading for our users, the default scale behaviour being surprising for those coming from CAD tools (road profiles, building cross sections, river bed, etc.).

[nyalldawson]

@Jean-Roc

Hi nyall, are you planning to present an option to set a "same scale axis" like in ProfileTool ?

It's not in the scope of the current project, but would definitely be possible!