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Bushy-tailed woodrat on midden Paleo-ecologists have used a variety of techniques to analyze the plant and animal material in pack rat middens describe paleo-communities and infer paleo-climate. For example, the plant species present in middens, and the carbon isotope ratios on material in middens have been widely studied.[7] " all depends on ...
The National Elevation Dataset (NED) consists of high precision topography or ground surface elevation data (digital elevation model) for the United States. It was maintained by the USGS and all the data is in the public domain. Since the 3D Elevation Program came online, the NED was subsumed [1] into The National Map as one of its layers of ...
The USGS Gap Analysis Program maintains four primary data sets: land cover, protected areas, species and aquatic. The GAP Land Cover Data Set is the most complete map ever produced of vegetative associations for the US. Classified into 551 ecological systems, and 32 modified ecological systems (where human impacts have had an effect).
Bryan also introduced Packrat as a parser that uses memoization techniques on top of a simple PEG parser. This was done because PEGs have an unlimited lookahead capability resulting in a parser with exponential time performance in the worst case. [2] [3] Packrat keeps track of the intermediate results for all mutually recursive parsing functions.
A pack rat midden is a debris pile constructed by a woodrat. A midden may preserve the materials incorporated into it for up to 50,000 years. [citation needed] These midden piles may be analyzed to reconstruct their original environment, and comparisons between middens allow a record of vegetative and climate change to be built.
Georeferenced map images are available from the USGS as digital raster graphics (DRGs) in addition to digital data sets based on USGS maps, notably digital line graphs (DLGs) and digital elevation models (DEMs). In 2015, the USGS unveiled the topoView website, a new way to view their entire digitized collection of over 178,000 maps from 1884 to ...
The North American Vertical Datum of 1988 (NAVD 88) is the vertical datum for orthometric heights established for vertical control surveying in the United States based upon the General Adjustment of the North American Datum of 1988.
SRTM data, being derived from radar, represents the elevation of the first-reflected surface—quite often tree tops. So, the data are not necessarily representative of the ground surface, but the top of whatever is first encountered by the radar. Submarine elevation (known as bathymetry) data is generated using ship-mounted depth soundings.