###	MEaSUREs InSAR-Based Antarctica Ice Velocity Map

###	Data accessed from https://doi.org/10.5067/D7GK8F5J8M8R on 2026-03-06
    Rignot, E., Mouginot, J. & Scheuchl, B. (2017). MEaSUREs InSAR-Based Antarctica Ice Velocity Map. (NSIDC-0484, Version 2). [Data Set]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/D7GK8F5J8M8R
    
### Description
    The MEaSUREs InSAR-Based Antarctica Ice Velocity Map is a gridded dataset of horizontal ice flow velocity derived from satellite radar interferometry and feature tracking. It contains the x- and y-components of surface ice velocity (VX, VY) at ~450 m spatial resolution, representing the mean ice flow between 1995 and 2016. This analysis computes the mean ice speed and flow direction, and generates a flow texture surface for visualisation.   
    
###	Processing steps:

    1.  Download antarctica_ice_velocity_450m_v2.nc from https://doi.org/10.5067/D7GK8F5J8M8R and file in cwd/input
    
    2.  Run 02_extract_tifs.py from cwd
        * Calculate ice speed (m/year) and ice-flow direction (0–360°, clockwise from north) from the VX and VY velocity components
        * Generate a Line Integral Convolution (LIC) flow texture at half resolution, globally normalise to 0–1, and resample back to the full source grid (bilinear resampling)
        * Retain native EPSG:3031 grid, standardise NoData to -9999, write separate speed, direction and texture COGs to cwd/output

### File description:

    * antarctica_ice_velocity_450m_v2_DIRECTION.tif = long-term mean ice-flow direction in degrees (0–360°, clockwise from north)
    * antarctica_ice_velocity_450m_v2_SPEED.tif     = long-term mean ice speed (m/year)
    * antarctica_ice_velocity_450m_v2_TEXTURE.tif   = greyscale flow texture for directional visualisation; suggested styling: 1 = black, 0 = white, 15–30% opacity