gpsmap: Routine for verifying and returning the attribute table of given decimal degree GPS coordinates

GPS coordinates are collected by many organizations, however in order to derive any meaningful statistical analysis from these coordinates they need to be joined with geographical data. Previously users were required to export the GPS data out of Stata and into a GIS mapping program to map the co-ordinates, validate them and join them to an attribute table. The results of which would then need to be imported back into Stata for statistical analysis. gpsmap is a routine that imports a user provided shapefile and its attribute table. Using a ray casting algorithm it maps the GPS coordinates to one of the polygons of the given shapefile and returns a dummy variable indicating whether or not the GPS coordinates were mapped successfully. Where the GPS coordinates were successfully mapped the attribute table applicable to that particular polygon is also returned to Stata. One of the contributions of gpsmap is to allow users to circumvent GIS Software and to incorporate GIS information directly within Stata. The other is to give users who are not familiar with GIS software the opportunity to use GIS information without having to familiarize themselves with GIS software.