Trees and foliage tutorial

Prerequisites

The following prerequisites should be met before starting this tutorial:

• The tutorial makes use of the Demo Heat Stress Project. If possible, a copy should be created because one of the steps involves uploading a new file. If this is undesirable, a file already present in the Project can be used. 

Preparations

Take the following steps as preparation for following this tutorial:

• Start the Demo Heat Stress Project.
• If possible, use a Save as operation to create a copy of the Project.

Tree and foliage data in general

There are a number of use-cases in which having accurate green data is relevant. In urban development, greenery has become an increasingly important spatial requirement. It also significantly impacts biodiversity and heat stress. It is therefore important to have as accurate data as possible related to the presence of green in an urban environment for a variety of simulation use-cases.

The Tygron Platform will, when a new Project of a real location is generated, automatically attempt to obtain open data about trees. However, depending on the use-case more accurate datasets may be required and available. In these cases, knowing how to properly manage data about trees (or foliage thereof) will improve the quality of calculations and thus the results.

For this tutorial, there will be a focus on using trees and foliage data with and for the Heat Stress Overlay, but the principles translate over to other use-cases as well.

Trees and foliage data in the Tygron Platform

In the Tygron Platform, trees are stored as a specific Function (or collection of Functions) of Buildings. By default, the Tygron Platform generates trees with the Function of "Default deciduous trees". Trees can exist as either small polygons (effectively points) to symbolize a single tree in a fixed location, or as a broader polygon to symbolize a group of trees (such as a treeline or a forest).

The visualization of trees is governed by a single Attribute or Function Value: FLOOR_HEIGHT_M. This Attribute, in amounts of meters, will affect how tall the tree is visualized.

For the Heat Stress Overlay, it isn't the trees data directly which is required for the calculations, but actually the foliage of the trees. The foliage casts significant shadows and thus affects the impact of solar radiation. By default, because there isn't a general datasource for foliage, the Tygron Platform's Heat Stress Overlay can instead derive an estimation of foliage from the trees data. This is done by effectively buffering the tree polygon with a certain amount of meters. That amount is determined by the FOLIAGE_CROWN_FACTOR, which is the ratio of foliage radius to tree height. This allows for a spatial dataset of foliage to be estimated based on the presence of trees.

For more information about how trees relate to the Heat Stress Overlay, consult the documentation:

• Foliage height calculation model (Heat Stress Overlay)
• Shade calculation model (Heat Stress Overlay)

Preparation

For the purpose of this tutorial, 2 datasets are needed, which can be obtained from the Public Share as is. Change a setting in the Heat Stress Overlay to establish a comparison baseline and connect it to the correct datasource.

Obtaining trees and foliage data

Go to:

Editor → Current Situation (Ribbon tab) → Geo Import (Ribbon bar) → Geo Share (Dropdown) → Public Share (top-right of the Geoshare window) (Window)

This provides access to the Public Share.

The Public Share.

Navigate to the following directory: tutorials/tutorial_trees_and_foliage/

The Public Share offers a number of files relevant for this tutorial.

The "trees data" GeoJSON file contains a vector dataset with some tree data of the environment of the Demo Heat Stress Project.

The "foliage data" GeoTIFF file contains a grid dataset with information about foliage heights in and around the Demo Heat Stress Project.

For all files, select them by clicking on them, and then access them by clicking on "Web Link". This will open the file in the web browser, and prompt a download.

The web link will open the file in the web browser, and either prompt a download or easily allow for a download.

Resetting foliage source of the Heat Stress Overlay

Ensure the Heat Stress Overlay has no initial foliage information to verify the import results.

Go to:

Editor → Current Situation (Ribbon tab) → Overlays (Ribbon bar) → PE Temperature (Left panel)

Select the PE Temperature Overlay.

In the right panel, click on "Configuration Wizard". This opens the Heat Stress Overlay Wizard.

Open the Wizard by clicking the button.

Continue to the step regarding Foliage.

The step for foliage. In the demo it is set to refer to another Overlay.

Opt to use "Tree Functions" height and foliage crown factor.

Change the setting to refer to the tree Functions.

Close the Configuration Wizard.

Click on "Update now" in the right panel to force the Overlay to recalculate.

Click on "Update now" to recalculate all Overlays in the Project.

Notice the results for the Project have changed. This is because the calculation now relies on a different dataset.

The results of the Heat Stress Overlay now that we changed the foliage setting.

Using trees data

An accurate dataset of trees will allow for an accurate counting of surface area used for the purposes of urban green. It can also be used by models such as the Heat Stress Overlay to extrapolate foliage from, which affects the calculations for heat stress.

Removing existing trees from the Project

Remove existing tree data before importing new data to prevent overlapping datasets from skewing calculation results.

Go to:

Editor → Current Situation (Ribbon tab) → Buildings (Ribbon bar) → Edit multiple Buildings (Dropdown)

Find the "Select Multiple Buildings" option.

In the bottom panel, an interface now allows for the mass-manipulation of multiple Buildings at the same time, based on Function and extent.

The panel which appears at the bottom of the screen.

As category, select "Specific Function".

As Function, select "Default Deciduous Trees". This is the default type of trees and means this operation will only affect trees.

Find "Default Deciduous Trees" in the "Nature" category.

As action, select "REMOVE"

The configured action for multiple Buildings.

Click on "Entire Map"

Use the "Entire Map"option to clear the applicable Buildings everywhere in the Project.

A prompt will appear. Confirming it will delete the 160 or so trees from the Project, leaving it without any trees data.

The confirmation prompt to perform the operation.

Editor → Current Situation (Ribbon tab) → Overlays (Ribbon bar) → PE Temperature (Left panel)

Click on "Update now" in the right panel to force the Overlay to recalculate.

Use this option again to recalculate all Overlays.

Notice the results for the entire Project are now significantly hot. This is because there is now no foliage data for the Heat Stress Overlay to work with.

The results of the PE Temperature Overlay after removing the trees, thus leaving the simulation without foliage.

Importing trees data

Go to:

Editor → Current Situation (Ribbon tab) → Buildings (Ribbon bar) → Import Geo data (Dropdown)

This opens the Geo Data Wizard.

Find the "Geo Data Import" option for Buildings.

As import method, select "GeoJSON file".

Select "GeoJSON file".

As GeoJSON file, click on "select local file". Select the previously downloaded trees geojson file.

Select the GeoJSON file you downloaded previously.

Take note of the "View features" step, where the locations of all trees are shown.

View the features to confirm whether the dataset is correct and where to expect the (new) data.

Also take note of the "buffer size" slider. when the dataset consists of points, all points will be buffered with the size indicated by the slider. By default all such points end up as polygons of exactly 1m² in size. Any polygons in the dataset will remain as-is.

Skip through the step for filtering features (all features are desired), adding or updating features (the default is to add, which is what we want to do), and the naming scheme (names are not relevant for calculations).

Filtering allows a subset of features to be imported, which is useful if the dataset contains, for example, removed trees as well.

Naming of the resulting features is not relevant for the purpose of calculations.

In the "Select Attributes" step, take note of the Attribute FLOOR_HEIGHT_M. This Attribute determines the height of the trees which are imported. If your dataset uses a different attribute for tree height, locate and rename it using the import text fields.

Take special note that whichever attribute represents the height of trees is imported as FLOOR_HEIGHT_M.

In the "Assign Functions" step, keep "One Function" selected, and click on "Select" to select the default function.

Select "Default Deciduous Trees", and continue to the next step.

Select the appropriate tree Function.

For the "Owner", select the Municipality.

The Municipal stakeholder is a good default for most import operations.

Continue to the last step of the Wizard and click on "Finalize" to add the data to the Project.

Go to:

Editor → Current Situation (Ribbon tab) → Overlays (Ribbon bar) → PE Temperature (Left panel)

Click on "Update now" in the right panel to force the Overlay to recalculate.

Recalculate all Overlays in the Project again.

Notice that in the areas where tree data was loaded in, the calculated temperature has dropped significantly.

The results of this data are especially notable outside the city centre, as that is where the data exists.

Also inspect the "Foliage" child Overlay of the Heat Stress Overlay, which shows the presence of foliage.

The locations of foliage can be seen to better understand the results of the calculation.

Using foliage grid data

Instead of relying on point data for trees, from which the Tygron Platform then extrapolates foliage coverage, it is also possible to supply a dataset of foliage directly. This is a grid of foliage heights which the Heat Stress Overlay can then use for its calculations.

Importing foliage grid data

Editor → Current Situation (Ribbon tab) → Overlays (Ribbon bar) → Custom, GeoTIFF Overlay (Dropdown)

Adding a new GeoTIFF Overlay from the dropdown.

A GeoTiff Overlay is now added to the list of Overlays, and selected.

In the right panel, switch to the "TIFFs" tab.

The TIFFs tab.

At the bottom of the right panel, click on "Add".

Click on "Add" to add GeoTIFFs to the Overlay to display.

A window appears which can be used to manage GeoTiff assets in a Project.

This screen allows for managing all GeoTIFFs uploaded to the Project.

Click on "Add local file", and select the previously downloaded GeoTIFF file.

Add local file allows the uploading of a file from the computer to the Project.

(Note that if the import of the file fails because you're working directly in the Demo Project, you can continue the rest of the steps with the already present "filteredtrees.tiff")

Select the imported tiff in the listing, and click "Ok".

After the import completes, the GeoTIFF can be selected and confirmed.

The tiff is now added to the listing.

The GeoTIFF is added to the Overlay.

Connecting foliage grid to Heat Stress Overlay

Go to:

Editor → Current Situation (Ribbon tab) → Overlays (Ribbon bar) → PE Temperature (Left panel)

In the right panel, click on "Configuration Wizard". This opens the Heat Stress Overlay Wizard.

Continue to the step regarding Foliage.

The foliage step of the Heat Stress Overlay's configuration wizard.

Opt to use a Grid Overlay to define the Foliage.

Change the configuration to refer to a Grid Overlay.

In the next step, select the newly added "GeoTIFF", which contains the foliage data.

Select the GeoTIFF Overlay added earlier.

Close the Wizard, and click on "Update now" in the right panel.

Again recalculate all Overlays.

Notice that in the areas with more foliage coverage according to the tiff, the calculated temperature has dropped significantly.

The temperature across the Project has changed.

Also inspect the "Foliage" child Overlay of the Heat Stress Overlay, which shows the presence of foliage.

The map of foliage is a lot more detailed.

Tutorial completed

Congratulations. You have now completed this tutorial. In it, you have learned how to import trees and foliage data, with an emphasis for use with the Heat Stress Overlay.