To always display coordinates as DMS values, add this to your common.css:
.geo-default { display: inline }
.geo-nondefault { display: inline }
.geo-dec { display: none }
.geo-dms { display: inline }
To always display coordinates as decimal values, add this to your common.css:
.geo-default { display: inline }
.geo-nondefault { display: inline }
.geo-dec { display: inline }
.geo-dms { display: none }
To display coordinates in both formats, add this to your common.css:
.geo-default { display: inline }
.geo-nondefault { display: inline }
.geo-dec { display: inline }
.geo-dms { display: inline }
.geo-multi-punct { display: inline }
If CSS is disabled, or you have an old copy of MediaWiki:Common.css cached, you will see both formats. (You can either clear your cache or manually refresh this URL: WIKI.org/w/index.php?title=MediaWiki:Common.css&usemsgcache=yes&action=raw&ctype=text/css&smaxage=2678400.)
To disable display of the blue globe adjacent to coordinates, add this to your common.js:
var wma_settings = {enabled:false}
Note that this will disable WikiMiniAtlas.
See also: OODA WIKI:Manual of Style/Dates and numbers § Geographical coordinates.