The 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 →
A 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.
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 →
A Digital Elevation Model (DEM) is a data set containing information about a terrains surface. In its most basic form it is a collection of geographical positions with associated elevation information. With this information it is possible to make visualizations or calculations which again can be used to understand how objects on the surface can interact.
As a geographer it is most of the time my job to facilitate for the use of spatial data. Working with elevation data is as fun as it gets, technically. The data sets lends themselves to nice visualizations and given the right questions the data sets might tell us interesting things about the relations between water, biological entities and masses. The much used watershed analysis results in an understanding of to which rivers water in an area drains. Among other things this is used to understand and manage water basins within the European Union.
For some years now there has been a discussion in Norway about the quality of our current elevation model. Most of us would agree that it could be better. I am one of them. In this posting I will try to give the reader some background to my view on this issue.