Look for complete geospatial metadata in this layer's associated xml document available from the download link


* Metric Name: Joshua Tree  

* Tier: 2  

* Data Vintage: 2003  

* Unit Of Measure: Binary layer, 1 represents current range, 0 not in range  

* Metric Definition and Relevance: This data set represents the digital range map of Joshua Tree ( _Yucca brevifolia_ ) in western North America. It is only found in the Southern California Region of California.  

* Creation Method: Data from multiple sources, including existing digitized maps, tabular data, personal communication, and figures from other publications, were synthesized to create a single digital distribution. Several steps were undertaken in the process of generating the final distribution. Paper map or figure sources were scanned using a flatbed scanner. Scanned images were then georeferenced in ArcMap (ESRI ArcGIS 8.3) using the Georeferencing Toolbar utilities. Once georeferenced, scanned images were then digitized using heads-up digitizing into respective shapefiles using ArcMap (ESRI ArcGIS 8.3). These shapefiles were then used, in conjunction with a digital elevation model (GTOPO30 from http://edcdaac.usgs.gov/gtopo30/gtopo30.html), to visually compare, edit, and generate a new distribution. Editing encompassed moving, adding, deleting, and reshaping polygons in the shapefile subjectively based upon visual comparison of all datasets in the GIS. Only polygons of species presence are included in the final version, and all polygons of presence have a CODE equal to 1. Once a draft distribution was completed, the distribution was distributed to regional experts and critically reviewed. Following review, the distribution draft version was iteratively edited and modified to meet the suggestions of the aforementioned reviewers. Subsequent review is possible, and the current version of this data set could be modified again in the near future based on feedback from existing and additional reviewers. The purpose of this digital data set is to delimit the modern geographic distribution of Joshua Tree ( _Yucca brevifolia_ ) based on existing publicly available data.

The polygons were then transformed to a binary 30m raster layer, where 1
represents Joshua Tree’s range.

Credits: Kenneth L. Cole, Keith Pohs, and John A. Cannella. U.S. Geological
Survey, Southwest Biological Science Center, Colorado Plateau Field Station

  

* Credits: USGS \--U.S. Geological Survey