This effort to map standardized, meso-scale ecosystems for both the conterminous United States and Africa is the first of its kind, and represents a biophysical stratification. The data developed for this mapping process were not all of the same quality or spatial resolution, but each dataset obtained and used for the mapping was considered to be "best available data" for that theme at a National extent. The primary goal for the first round of this mapping effort was to utilize the best source data currently available to generate a first iteration of ecosystems as quickly as possible. This goal was framed on the logic that reasonably robust and satisfactory results could be obtained from this method without a multi-year, million-plus dollar investment, and the methodology would therefore prove suitable for application in the global ecosystems mapping project under GEOSS.
As such, these data should be considered as first generation, first iteration products assembled specifically for the purpose of delineating ecosystems in a standardized manner. The input layers that represent interim products in the geospatial delineation of ecosystems should not be construed, in and of themselves, as "definitive" products. All these products could be improved in terms of strength of concept, quality of source data, and spatial resolution. These data should therefore be considered as representative of a first iteration attempt to use best available data to model standardized ecosystems, and improvements in the data input layers and final products all have the potential to be improved over time, in subsequent iterations.
Based on the nature of this first iteration of products, the following potential issues were already identified for two of the ecosystems data layers generated for the conterminous United States:
Data artifact transfer from CTI source data to Topographic Moisture Potential
1) Topographic Moisture Potential - This dataset was derived from the Compound Topographic Index (CTI) dataset, which was itself a derivative product of the National Elevation Dataset (NED), created by the Elevation Derivatives for National Applications (EDNA)
project. Therefore any data artifacts found in either the CTI dataset or NED were inherited in the Topographic Moisture Potential dataset. These artifacts appear as grid patterns in the Topographic Moisture Potential and can be found in areas of flatter terrain. The Topographic Moisture Potential dataset also includes small occurrences of No Data areas, with a pixel value of zero, based on No Data areas in the CTI dataset. No attempt was made to eliminate these artifacts or No Data pixels from the derived dataset; however, additional efforts are planned to research the effects of these issues.
2) Land Surface Forms - This dataset was derived from the NED based on various neighborhood analysis using a 1-km2
analysis window. However, it was determined that the NED did not include sufficient elevation data on Canadian side of the northwestern U.S.–Canada border. As a result, in the areas within approximately 600-meters to the south of this border, neighborhood analysis were run with insufficient input data therefore land surface form classes in this area are expected to have lower accuracy.