Tag Archives: qdgc

QDGC-files updated

qdgc_logoThe Quarter Degree Grid Cells (QDGC) data set has been updated. It is well over a year since last time. Some errors in the current release has made this necessary.

One of the things which kept me from doing the update was the rather complicated python-scripts combined with using the arcpy-library. The whole process was in it self complex. I dreaded sticking my head down into the python/arcpy/manual processing soup.

Through the last year or so I have started using FME more and more. Once you know a tool well you start thinking – what if… So I thought – what  if I instead of going one more round with python and arcpy tried solving this challenge using FME? Continue reading

QDGC shapefiles available for national and continental scale distribution

Aqdgc_logo new set of the Quarter Degree Grid Cell shapefiles has been generated. The update is global and delivers an error fix for the country level files as well as a new product – continent level files.

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. Continue reading

QDGC global coverage level 1-4

Aqdgc_logo new set of the Quarter Degree Grid Cell shapefiles has been generated. This time the coverage is global and the publication is for individual countries.

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. Continue reading

QDGC – Quarter Degree Grid Cells revisited

Some years ago I wrote a paper on Quarter Degree Grid Cells. Quarter Degree Grid Cells (QDGC or QDS – Quarter degree Squares) is a way of dividing the longitude latitude degree square cells into smaller squares, forming in effect a system of geocodes. Historically QDGC has been used in a many African atlases. Several African biodiversity projects uses QDGC, among which The atlas of Southern African Birds is the most prominent one.

In this posting I will present the paper and explain the general principles of the QDGC standard. Parts of the posting is from the wikipedia article describing the standard. I wrote that article so if there is any resemblance with Wikipedia there is an explanation to it. Continue reading