Urban Vegetation Data - Canopy Height Model (Brussels Capital Region, 2021)

This GIS dataset was created for the following scientific publication, as part of the EU-funded Cool Schools research project (under Grant Agreement No. 101003758) : Gallez, E., Canters, F., Gadeyne, S., & Baró, F. (2024). A multi-indicator distributive justice approach to assess school-related green infrastructure benefits in Brussels - ScienceDirect. Ecosystem Services, 70, 101677. https://doi.org/10.1016/j.ecoser.2024.101677. 

Very-High Resolution Canopy Height Model (resolution : 25cm), distinguishing between 4 vegetation types (trees, high shrubs, low shrubs and grass) in the Brussels Capital Region.

Coordinate system : Lambert_Belge_72.

The CHM was built on :

• VHR aerial orthophotos (visible RGB and NIR) (“UrbIS-Ortho N-S, 2021”) for the Brussels Capital Region, of 5x5cm resolution  Source: Paradigm. (2021). UrbIS-Ortho N-S. Paradigm.Brussels. https://datastore.brussels/web/urbisdownload.  and;
• digital terrain models (DSM and DTM) of 50x50cm, captured on 22/09/2021. Paradigm.Brussels. Source: Paradigm. (2021). DSM / DTM. Paradigm.Brussels. https://datastore.brussels/web/urbisdownload.

Both the orthophotos and digital terrain models were resampled to a 25x25cm resolution, using a bilinear interpolation method.

The Canopy Height Model was then created by selecting NDVI values of 0.2 and higher, - a commonly used threshold value to distinguish vegetated land from built land (Hashim et al., 2019) -, and vegetation height thresholds of < 0.5m (for grass), 0.5 - 2m (for low shrubs), 2 - 5m (for high shrubs), and > 5m (for trees) (Derkzen et al., 2015; Sankey et al., 2018). Green roofs were excluded.The CHM raster was then converted to polygon features. 

Classification :

• From 0 to 0.5 m (nDSM value) : gridcode 1 = grass
• From 0.5 to 2 m (nDSM value): gridcode 2 = low shrubs
• From 2 to 5 m (nDSM value): gridcode 3 = high shrubs
• From 5 to 113.96 m (nDSM value): gridcode 4 = trees