Information GMBA_2021_Mountain_Rasters_V2 (release 4)
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May 2021 (release 4)

This document describes the files contained in the zip folder "GMBA_2021_Mountain_Definition.zip"

The folder contains the following 3 GeoTiff files:
1. GMBA_2021_Ruggedness_EarthEnv_30s16Bit.tif
2. GMBA_2021_MntnMask_EarthEnv_30s1Bit.tif
3. GMBA_2021_RuggednessMntnMask_EarthEnv_30s16Bit.tif


Technical notes:
1. The ruggedness and mountain definition (MntnMask) layers are presented at 30" resolution and are calculated based on Körner et al. (2011): https://link.springer.com/article/10.1007/s00035-011-0094-4

2. The coordinate reference system (CRS) of all files is WGS 84 / EPSG:4326

3. Source data: 
- EarthEnv 1Km median elevation. The choice for this 30 arc second (approximately 1km) resolution DEM was made because it is a high quality DEM with global coverage including Greenland.
	- EarthEnv http://www.earthenv.org/topography: Derived topographic continuous variables
	- Dataset: Elevation;
	- Aggregation: Median; 
	- Sources: GMTED2010; 
	- Resolution: 1km. 
	- The downloaded file is called: elevation_1KMmd_GMTEDmd.tif

4. The following three files were created in May 2021 using ArcGis 10.8.1 


File description: 

FILE 1: "GMBA_2021_Ruggedness_EarthEnv_30s_V2.tif": ruggedness at 30 arc second resolution
- The 30 arc second ruggedness layer was calculated by taking the elevation range (maximum elevation - minimum elevation) within a square 3 x 3 neighbourhood analysis window (NAW) using the Focal Statistics (Spatial Analyst) tool and elevation_1KMmd_GMTEDmd.tif as input.
- Output file size was minimized by applying LZW lossless compression and setting the pixel type to 16 bit unsigned.
- Values of the grid represent the ruggedness (elevation range) in m.

FILE 2: "GMBA_2021_MntnMask_EarthEnv_30s_V2.tif": GMBA Mountain Mask (or "mountain definition") at 30 arc second resolution
- This layer is a binary layer
- For this layer, the cells of the "GMBA_2021_Ruggedness_EarthEnv_30s_V2.tif" layer were reclassified using the Raster Calculator (Spatial Analyst) tool:
elevation range >= 200m = 1 other values = NoData
- Output file size was minimized by applying LZW lossless compression and setting the pixel type to 1 bit.

FILE 3: "GMBA_2021_RuggednessMntnMask_EarthEnv_30s_V2.tif": ruggedness corresponding to mountain definition only at 30 arc second resolution
- In this layer the cells of the "GMBA_2021_Ruggedness_EarthEnv_30s_V2.tif" layer were reclassified using the Raster Calculator (Spatial Analyst) tool and the following conditional statement: Con(GMBA_2021_Ruggedness_EarthEnv_30s_V2.tif>=200,GMBA_2021_Ruggedness_EarthEnv_30s_V2.tif)
that is: in case roughness is greater or equal to 200, then attribute roughness, else attribute NoData to the cell
- Output file size was minimized by applying LZW lossless compression and setting the pixel type to 16 bit unsigned.
- This layer represents a nice way to visualize mountain topography


IMPORTANT: these layers were calculated based on a different DEM and at a different resolution than previous layers that are included in release 2&3 and were generalized from 30” to 2.5’. This causes differences in total areas of mountainous terrain.  

How to cite:
When using the GMBA ruggedness data, please cite:  
1. Publication: Körner C, Paulsen J, Spehn E (2011) A definition of mountains and their bioclimatic belts for global comparisons of biodiversity data. Alpine Botany 121(2): 73-78 DOI:10.1007/s00035-011-0094-4. 
2. Data: DOI:10.7892/boris.83486