When we first started developing the processing software for the ivp, we had to make some decisions about the geographical extent we would process. As this dataset was conceived of as pertaining to those interested in forests, we used a variety of forest maps (e.g. the MODIS landcover and continuous fields products) to create a 1000m resolution mask of forested areas. We then tallied, on a 1 x 1 degree grid, the percent of 1000m pixels that were considered forest. When more than 10% of the 1 x 1 degree grid cell was forest, we flagged that cell as one that we would process. These 1-degree cells were then used to create a 5 x 5 degree grid (the basic unit of data distribution), where the presence of a single forested 1-degree cell was considered enough to flag that 5-degree cell as forest. These were then aggregated to cells that were approximately 20 x 20 degrees, which were used for our data requests to NASA. This largest scale of aggregation remains as a secondary scale for data distribution.
We recognize that, while these rules selected the vast majority of global forests, there are some forested areas that have not been processed. For instance in eastern China, there exist patches of forest which were not large enough to pass the "10% of 1-degree cell" criteria and were therefore excluded. We expect that other areas were missed as well.
The bottom line is that we only need to know what areas you need to have included in the dataset and we should be able to add then relatively quickly. Updates to the database will be shortest for those 5-degree grid cells that fall within the 20-degree subsets. Otherwise, we will need to make a new data request from NASA and that will take additional time.
Please post requests for adding additional areas to the ivp dataset as responses to this thread.
Tuesday, February 6, 2007
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