function [mn,mx]=meshdl(fem_grid_struct)
%MESHDL determine the minimum and maximum element edge lengths
% MESHDL determines the minimum and maximum grid element edge lengths,
% suitable for use is a Courant number estimate.  MESHDL trys to
% determine if the input mesh is in Lat/Long of meters.  
%
%  Input  : fem_grid_struct - OPNML mesh structure 
%
% Output  : mn,mx - minumin and maximum element edge lengths.
%                   returned in meters!!
%
% Call as :  [mn,mx]=meshdl(fem_grid_struct);
%
% Written by: Brian Blanton, Jun 1999


if nargin~=1
   error('MESHDL must have a valid FEM_GRID_STRUCT as input.')
else
   if ~isstruct(fem_grid_struct)
      error('Argument to MESHDL is not a structure.')
   elseif ~is_valid_struct(fem_grid_struct)
      error('FEM_GRID_STRUCT to MESHDL is not a valid grid structure.')
   end
end

% Try to determine if the grid is lon/lat
minx=min(fem_grid_struct.x);
maxx=max(fem_grid_struct.x);
miny=min(fem_grid_struct.y);
maxy=max(fem_grid_struct.y);

gxy=fem_grid_struct; % Copy struct

if (maxx-minx)<90 | (maxy-miny)<90
   % grid appears to be in degrees
   gxy.x=deg2km(fem_grid_struct.x)*1000;
   gxy.y=deg2km(fem_grid_struct.y)*1000;
end

gxy=belint(gxy);
dx=gxy.A;
dy=gxy.B;
dxy=sqrt(dx.*dx+dy.*dy);

mn=min(min(dxy));
mx=max(max(dxy));