Building a global cropland mask, is not an easy task

Criticizing is easy, and doing is hard, especially when trying to create a global map of croplands. Some collegues from CESBIO have worked on that subject within the Sen2Agri project, and obtained good resuts, but only at the local or country scale. Finding a method that works everywhere must clearly be much harder.

These days, I have received a lot of emails, tweets and posts about a new cropland global product at 30 m resolution, edited by USGS. I have no doubt it was a serious work from a serious team, done with appropriate terrain data and methods, validation, and of course a tremendous data processing.

 

 

But there it is, I checked it over a lot of places that I know very well, and it seems to me that the cropland mask, at least in South West France, is clearly overestimated. Is it the same in tour region ? Here are some examples :

An extract over the pyrenees, where cropland are found even above 2000m above sea level.

Toulouse town center seems to be also quite covered by croplands, including the airport greens and city parks. Even the green yard next to CESBIO is cropland.

The basque country is known for its meadows, and nice scenery, as well as frequent rain. These regions migh have a few corn fields, but most of the ones detected by USGS are meadows, or even heather or fern moors

I took some more examples, randomly, in Spain and Scotland, where the results look alike :

Here again, in castilla, with some forest and this typical castillan landscape, la dehesa, extensive rangeland where black pigs are fed to get the best ham in the world (but that's not the subject of the post)

Scottish highlands, where no cropland should be detected except in the Eastern part maybe

 

I did not find much information about the cloud mask validation in USGS data release. Maybe will it come soon, or did I overlook the articles ? As I have heard similar comments from colleagues in Belgium or Italy, this does not give too much confidence in the 15-20% increase figure quoted in the articles. But maybe the issue is only in Europe, and will be solved in next version ?

 

Posted under: Applications, In English, Land cover - Occ.des sols, Landsat

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