ekkoread(datafile,varargin)

function [x,t,A,hdr] = ekkoread(datafile,varargin)
% EKKOREAD Import a WinEKKO Ground Penetrating Radar File (.as2). 
%   [x,t,A] = EKKOREAD('FILE') reads an ascii Sensors & Software WinEkko 
%   export file (.as2 extension). Output values are:
%   x: vector of trace positions in x direction.
%   t: vector of travel times
%   A: apmlitude data array
%   hdr: srtucture array of parameters from headerfile in field .name and 
%   .value (empty if no headerfile exists).
% 
%   EKKOREAD('FILE','HEADERFILE') uses the specified headerfile. Default =
%   'FILE.dh'.
%  
% Ian M. Howat, Applied Physics Lab, University of Washington
% [e-mail]
% Version 1: 06-Oct-2005


A= DLMREAD(datafile,' ',1,0);
t = A(:,1); A(:,1) = [];
x = str2num(fgetl(fopen(datafile))); fclose all;


if isempty(varargin)
    headerfile = [datafile(1:find(datafile == '.')),'hd'];
else
    headerfile =  varargin;
end

if ~exist(headerfile,'file')
    disp('>> Header file does not exist, no header information returned');
    hdr = [];
else
    
    fid = fopen(headerfile);
    i=1;
    while i
        line = fgetl(fid);
        if ~isempty(line); 
            if line == -1;
                break   
            elseif ~isempty(find(line == '=')) &&  isempty(str2num(line(1)))
                hdr(i).name = line(1:find(line == '=')-1);
                tmp = line(find(line == '=')+1:end);
                if isempty(str2num(tmp))
                    hdr(i).value = tmp;
                else
                    hdr(i).value = str2num(tmp);
                end
                i =i+1;
            end      
        end
    end
end
fclose all;