On Sun, May 18, 2014 at 9:29 AM, Rolf Turner <r.turner at auckland.ac.nz> wrote:
On 18/05/14 14:35, Hossain, Md wrote:
Very grateful to Rolf and Adrian for your kind suggestions. Obviously I am going to follow, but it seems there is no quick fix. In the mean time, just wondering, is there anything that I can do with the "map2SpatialPolygons" function. The data came with the long-lat, but no information about how these long-lats are created, i.e., whether using "WGS84" is apropriate or should I try for other options, e.g., for GCS_North_American_1983_HARN. My knowledge in geography is very poor, please help.
Have you done whats been suggested and plotted the points to see *why* the points are thought to be outside your map? Various things can happen with data: x and y coordinates get swapped x and y coordinates are set to 0,0 or -999,-999 to make missing data numbers get typed in wrong minus signs in western or southern hemisphere coordinates get left off locations are rounded to the nearest 100m, then converted to lat-long etc the other problem is that the boundary is an APPROXIMATION to the border. To keep the dataset size small enough, a lot of the wiggly coastline is approximated by a straight line. If you have points near the coast then some may end up on the wrong side of the approximated line. Is that what's happening? Have you plotted the points? don't go messing around with projections and datums (which might only move points by a few metres) until you've had a look at why the points are outside your polygon. Barry