How to make your coordinates WGS84 with mapshaper.org
If you upload your GeoJSON and your map doesn't seem to display, the coordinates in your GeoJSON are probably not WGS84. You can get a reasonable idea of this by looking at a few of the (multi)polygons. If WGS84 is being used then the coordinates should all represent longitudes and latitudes and be between -180 and 180 and -90 and 90, respectively. If the numbers are outside this range then they don’t represent longitudes and latitudes and so can’t be WGS84.
To transform your coordinates to be WGS84, you can use the free online tool mapshaper.org.
Import your GeoJSON to mapshaper.org
Open the console and enter the command "-proj wgs84"
- Export as GeoJSON
- Upload your new GeoJSON to the projection map template and see your map appear in the bottom right corner