The QDGC shapefiles contain center lon/lat coordinates and the QDGC string for the different squares. The files are offered down to level four. For a country around the equator level four covers around 45 square kilometers with length and height a little under seven kilometres.
Read more about the use of QDGC on this page:
The calculations/export this time took around 60 hours computer pricessing time including generation of world fishnet with the different sizes, square area calculations, assigning QDGC strings, compression and more.
The below images shows how quarter degree grid cells covers Uganda.
Since last time I have moved the files to my own server. Figured out I wanted to have statistics for the files. The naming convention in the below list is based on the ISO 3166-1 alpha-3 standard. This means that the first three letters in the files below indicate which country the file is for. UGA is for example for Uganda.
This i s a list of the continents level files:
[wpfilebase tag=list id=12 tpl=table pagenav=1 /]
Here is a list of countries level files:
[wpfilebase tag=list id=10 tpl=table pagenav=1 /]
The associated code for generating the QDGC is kept in the following project on github:
The error mentioned on the country level QDGC files was related to level 3 only where the grid set was somewhat off and thus not in compliance with the standard. It has been fixed now.