I'm trying to generalize World Bank Official Boundaries:World Boundaries GeoJSON - Low Resolution from https://datacatalog.worldbank.org/dataset/world-bank-official-boundaries using QGIS 3.18.3, using GRASS v.generalize, ultimately to display data using vega-lite, but some shapes aren't generalizing
Firstly, I removed the "fid" field, since that fixes issues about unique constraint violations. Then, I run the v.generalize with all the default options, which are
{
'-l' : True,
'-t' : False,
'GRASS_MIN_AREA_PARAMETER' : 0.0001,
'GRASS_OUTPUT_TYPE_PARAMETER' : 0,
'GRASS_REGION_PARAMETER' : None,
'GRASS_SNAP_TOLERANCE_PARAMETER' : -1,
'GRASS_VECTOR_DSCO' : '',
'GRASS_VECTOR_EXPORT_NOCAT' : False,
'GRASS_VECTOR_LCO' : '',
'alpha' : 1,
'angle_thresh' : 3,
'beta' : 1,
'betweeness_thresh' : 0,
'cats' : '',
'closeness_thresh' : 0,
'degree_thresh' : 0,
'error' : 'TEMPORARY_OUTPUT',
'input' : '/home/dw/Desktop/WB_countries_Admin0_lowres.geojson',
'iterations' : 1,
'look_ahead' : 7,
'method' : 0,
'output' : 'TEMPORARY_OUTPUT',
'reduction' : 50,
'slide' : 0.5,
'threshold' : 1,
'type' : [0,1,2],
'where' : ''
}
I get a good amount of warnings in the output, but it does make a new layer
WARNING: Number of incorrect boundaries: 2205
WARNING: The combination of types is not supported by all formats.
WARNING: No attribute table found -> using only category numbers as attributes
WARNING: 3668 features without category were skipped. Features without category are written only when -c flag is given.
WARNING: Output layer is empty, no features written
WARNING: 2237 boundaries were not modified because modification would damage topology
WARNING: 3638 lines/boundaries were not modified due to over-simplification
Spain looks generalised, but France and the UK, no. (Technically Spain is more generalized than I want, but expect that's a matter for tweaking the tolerance)
I can sort of understand this from the warnings... but what I don't know: what to do about it. How can I get all the countries to generalise? I would like the boundaries of countries to remain aligned without gaps appearing between them.
