Map Layers and Data Products
Developed by the Joint Research Centre (JRC) of the European Commission, the GLC-2000 was derived from SPOT 4 satellite imagery at a resolution of 1km. The MODIS land cover product (MOD12Q1 V005), at a resolution of 500mm, was created by Boston University using the Moderate Resolution Imaging Spectoradiometer instrument on the NASA Terra Platform. Version 5 (MOD12Q1 V005) for the year 2005 is the most recent product available. GlobCover was developed at the JRC in collaboration with other European partners as European Space Agency (ESA) initiative using data from the MERIS sensor on-board the ENVISAT satellite. GlobCover 2005 is intended to update and complement existing comparable global products such as the GLC-2000 and provide a finer spatial resolution (300m). The latest version is GlobCover 2009.
In addition to the global land cover maps, users can also view maps of spatial disagreement on Geo-Wiki. An example is provided in Figure 1. The disagreement was determined by examining the amount of definitional overlap between legend categories as described in Fritz et al. (2011) and expressed in the form of lookup tables. The lookup tables were then applied to each pair of land cover products to create maps of disagreement in forest, cropland and combined domains. These maps were created to highlight those areas where the global global land cover products currently disagree and to then target our crowdsourcing efforts towards validating these areas using Google Earth. These disagreement maps have been registered in the Global Earth Observation System of Systems (GEOSS) portal so users can display them using a Web Map Service (WMS) or Web Coverage Service (WCS).
Figure 1: An example showing the disagreement between the GLC-2000 and MODIS in the cropland domain.
The third data product available on Geo-Wiki is the set of validations provided by the users along with photos uploaded via geo-wiki.org or Geo-Wiki mobile. The data provided by the users are stored in a Postgresql database along with their registration information. A subset of these contributions was used to validate a hybrid cropland map in Africa (Fritz et al. 2011), which can be viewed and downloaded from agriculture.geo-wiki.org, as well as a map of land availability for biofuel energy production (Fritz et al., submitted). Users can download their own validations as well as the validations of all other users from the site, which they can use for their own purpose.
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