Land cover is raster (pixel) geographic data where each pixel represents a single type of land. Land cover makes it possible to identify and quantify how much of a region (a town, a watershed, a state, etc.) is covered by each land cover class, such as forest, wetlands, impervious surfaces, and agriculture and where. Land cover is different from an aerial or satellite image taken from above. Even those these images may have coordinates and know location, their land cover type can not be easily quantified.
Landsat satellite imagery (30 meter pixels)
Changing Landscape Land Cover (~30 meter/100 foot pixels)
Aerial Imagery (3 inch pixels)
High Resolution Land Cover (1m pixels)
Factors to Consider when Using Land Cover
Spatial resolution is how much land is covered by one pixel. The smaller the area, the more spatial detail, and the larger the file size.
Although high resolution land cover is fantastic, there are benefits to medium resolution including:
- ability for change analysis since there are older dates,
- ability to seamlessly cover large areas, and
- ease and cost of production.
Number of Classes
The number of classes in a land cover dataset can very widely, from very few (forest, water, developed, other) to many. For example, one land cover dataset may have a "wetlands" class where another may have 6 wetland classes (palustrine forested wetland, palustrine scrub/shrub wetland, palustrine emergent wetland, estuarine emergent wetland, etc.). Classes can be combined to be broader, but it takes work to make them more specific.
When was the imagery that was used to create the land cover captured?
There is always error associated with the process of converting and image to land cover. Accuracy assessments report the overall error, as well as class-specific errors (commission and omission). Some errors are more problematic than others. For example, mistaking a forest for developed could be a bigger issue than mistaking a wetland for a forested wetland.
Two types of Land Cover: Medium Resolution and High Resolution
The medium resolution land cover is called Connecticut's Changing Landscape. The Changing Landscape project is a long term, remote sensing-based land cover study that charts landscape changes in Connecticut and portions of New York. It covers the 30-year period from 1985 to 2015 (with in-between dates of 1990, 1995, 2002, 2006 and 2010). It also includes subsidiary analyses such as forest fragmentation, riparian area analysis, impervious surface analysis, and more. The availability of satellite imagery starting in 1985 has made it possible for long-term change mapping.
The high resolution land cover offers tremendous detail in both spatial resolution (LOTs of pixels) and number of classes making it useful in many disciplines. Currently there is just one date (2016) making it impossible to use for change. We are working towards more high resolution land cover in the future.