Please bear in mind that the ISPRS report is not what any one entity has collected or produced, but rather an assessment of collectively what has been produced by all countries worldwide.
Broadly speaking, the 1:50K gaps (not produced by anyone, even the mapping agencies of the respective countries) include:
- North America: no gaps except for Greenland. Even Canada is complete although mostly unpublished
- South America/Caribbean: only significant gaps are in the interior parts of Brazil and in adjacent areas of most countries bordering Brazil
- Europe: complete
- Former Soviet Union: complete
- Africa: very incomplete in the Sahara countries, DRC and Congo-Brazzaville, CAR. Somalia, Sudan/South Sudan, Cameroon, Gabon; complete or mostly complete in nearly all other countries.
- Middle East: complete except for interior parts of KSA, Yemen and Oman, where there is complete 100K, though.
- South Asia/SEA/Far East: complete
- Australia/NZ/Oceania: complete except for PNG and possibly the interior of Australia (but both covered by good 100K)
- Antarctica: mostly incomplete
So perhaps in total there is 25-30% of the Earth’s land surface not yet covered in 50K or greater; maybe 15-20% if you exclude Antarctica and Greenland.
And being mapped once is not the same as regular updating, of course. Lots of the 50K mapping is decades old and hence lacking all the (often Chinese) infrastructure as well as indigenous cultural features and changing water conditions.
Somalia is not mapped well yet, but I would not be surprised if that was changing in Mogadishu. The MGCP program has heavily covered Africa and the Middle East, including all of Somalia, but I’d imagine a lot of this data is in vector GIS format and not cartographically finished. Vector GIS is fine if you know how to use GIS or have apps that do. But it’s not the same as cartographic finishing, which results in a standard TLM-type product (raster/PDF or paper) which can be used by anyone.