read_side_scan_sonar_dvs.m

function [side_scan_data] = read_side_scan_sonar_dvs(file_name)
% Read Side Scan Sonar file generated by DeepVision Sonars
%
% Input-
% file_name: The name of the file that contains the sonar data in *.dvs
% file format
%
% Output- 
% side_scan_data structure, with the following contents:
% side_scan_data.src, the source file name (same as input)
% side_scan_data.res: Ping resolution [m] across track
% side_scan_data.nSamples: The number of samples per ping per channel(side)
% side_scan_data.left: Left side sonar data 2D(ping ix, sample ix)
% side_scan_data.right: Right side sonar data 2D(ping ix, sample ix)
% side_scan_data.lat: Latitude in [rad]
% side_scan_data.lon: Longitude in [rad]
% side_scan_data.heading: Sonar heading in [rad]
% side_scan_data.speed: Vehicle speed in [m/s]
% 
%
%
% Author: Fredrik Elmgren DeepVision [fredrik@deepvision.se]
% Date: May 11, 2016
%
% Example: 
% [x] = read_side_scan_sonar_dvs('WE1.dvs')
%
%
%
%
% Project SWARMs http://www.swarms.eu/
%
% License:
%=====================================================================
% This is part of the UNDROIP toolbox, released under
% the GPL. https://github.com/rawi707/UNDROIP/blob/master/LICENSE
% 
% The UNDROIP toolbox is available free and
% unsupported to those who might find it useful. We do not
% take any responsibility whatsoever for any problems that
% you have related to the use of the UNDROIP toolbox.
%
% ======================================================================
%%

tic;
% Constants
SIZE_FILE_HEADER = 4+4+4+4+1+1+2;
SIZE_PING_HEADER = 8+8+4+4;

% File handler
fileID = fopen(file_name,'rb');
if fileID == -1 
    fprintf('Could not open file %s \n', file_name);
    side_scan_data=[]; % just to get rid of the useless warnning
    return;
end

side_scan_data.src = file_name;

% file length
fseek(fileID, 0, 'eof');
file_length = ftell(fileID);
fseek(fileID, 0, 'bof');

% version
file_version = fread( fileID, 1, 'int32');
%side_scan_data.file_version = file_version;

if file_version == 1 
    
	% Read Header
 	side_scan_data.res = fread( fileID, 1, 'float' );
 	fread( fileID, 1, 'float' ); % Skip 1 float(line rate)
 	side_scan_data.nSamples = fread( fileID, 1, 'int32' );
 	side_scan_data.leftActive = fread( fileID, 1, 'int8' );
 	side_scan_data.rightActive = fread( fileID, 1, 'int8' );
    
    %Read 2 padded bytes
    fread( fileID, 1, 'int8' );
    fread( fileID, 1, 'int8' );
        
    if( side_scan_data.leftActive > 0 ) && ( side_scan_data.rightActive > 0 )
        side_scan_data.number_of_ping = round( (file_length-SIZE_FILE_HEADER)/(2*side_scan_data.nSamples+SIZE_PING_HEADER) );
    else
        side_scan_data.number_of_ping = round( (file_length-SIZE_FILE_HEADER)/(side_scan_data.nSamples+SIZE_PING_HEADER) );
    end
    
    % Read Ping data
    side_scan_data.left = zeros(side_scan_data.number_of_ping,side_scan_data.nSamples, 'double');
    side_scan_data.right = zeros(side_scan_data.number_of_ping,side_scan_data.nSamples, 'double');
    side_scan_data.lat = zeros(side_scan_data.number_of_ping,1);
    side_scan_data.lon = zeros(side_scan_data.number_of_ping,1);
    side_scan_data.heading = zeros(side_scan_data.number_of_ping,1);
    side_scan_data.speed = zeros(side_scan_data.number_of_ping,1);
    
    for i=1:side_scan_data.number_of_ping
        % Read Ping Header Data
        side_scan_data.lat(i) = fread( fileID, 1, 'double' ); 
        side_scan_data.lon(i) = fread( fileID, 1, 'double' ); 
        side_scan_data.speed(i) = fread( fileID, 1, 'float' );
        side_scan_data.heading(i) = fread( fileID, 1, 'float32' ); % in rad 
        
        % Read Ping Received Signal Strength
        side_scan_data.left(i,:) = fread( fileID, side_scan_data.nSamples, 'uint8' );
        side_scan_data.right(i,:) = fread( fileID, side_scan_data.nSamples, 'uint8' );        
    end
            
end

fclose(fileID);

fprintf('Time needed to read the image is %.2f second(s) \n', toc);