updateMetaData.m

function metaData = updateMetaData(metaData,Header,GPS,seq,stat,dupl)

% metaData = updateMetaData(metaData,Header,GPS,seq,stat,dupl)
%       
% If the metaData structure has changed since
% this file was written, update it
%
% Last modified by A. Kelbert, 1 June 2018

fields = fieldnames(metaData);
oldMetaData = metaData;
instrumentType = metaData.InstrumentType;

if isnumeric(metaData.dt)
    HZ = 1/metaData.dt;
else
    HZ = 1/str2double(metaData.dt);
end

if nargin >= 5
    metaData = initMetaData(Header,GPS,seq,stat,dupl,HZ,instrumentType);
elseif nargin <= 1
    metaData = initMetaData;
else
    error('Please specify Header, GPS, seq and stat strings');
end
    
i = find(strcmp(fields,'NIMS'));
if i>0
    metaData.InstrumentType = 'NIMS';
    metaData.InstrumentID = oldMetaData.NIMS;
end

i = find(strcmp(fields,'nims_comments'));
if i>0
    metaData.field_comments = oldMetaData.nims_comments;
end

if nargin <= 1
    % in this case only add new fields
    for k=1:length(fields)
        if isfield(metaData,fields{k})
            metaData.(fields{k}) = oldMetaData.(fields{k});
        end
    end
else
    % in this case, trust the newly computed times and errors, etc.
    for k=1:length(fields)
        if isfield(metaData,fields{k})
            switch fields{k}
                case {'startDate', 'endDate'}
                    % if new date is a valid date, leave it; new logic is
                    % to also trust the XML file over GPS is GPS_ERROR=1 
                    if strcmp(metaData.(fields{k}),'yyyy-mm-dd') || metaData.GPS_ERROR
                        metaData.(fields{k}) = oldMetaData.(fields{k});
                    end
                case {'startTime', 'endTime'}
                    % if new time is a valid time, leave it; new logic is
                    % to also trust the XML file over GPS is GPS_ERROR=1 
                    if strcmp(metaData.(fields{k}),'HH:MM:SS') || metaData.GPS_ERROR
                        metaData.(fields{k}) = oldMetaData.(fields{k});
                    end
                case {'lat', 'lon'}
                    % if new coordinates are more accurate, use them
                    if abs(metaData.(fields{k}) - oldMetaData.(fields{k})) < 0.001
                        % use new values (previously truncated them early)
                    else
                        metaData.(fields{k}) = oldMetaData.(fields{k});
                    end
                case {'elev'}
                    % as of 2020, elevation seems more robustly computed.
                    % Use that.
                case {'decl'}
                    % as of 2020, we use IGRF to compute the declination,
                    % to replace the old GNSS NMEA sentence with outdated
                    % world magnetic model. Overwrite the old values!
                    % ... but do this AFTER lat,lon,elev & time are updated
                case {'nscan'}
                    % if valid, use new value, else leave the old one
                    if metaData.(fields{k}) <= 0
                        metaData.(fields{k}) = oldMetaData.(fields{k});
                    end
                case {'InstrumentID', 'Magnetometer'}
                    % always explicitly use the old values
                    metaData.(fields{k}) = oldMetaData.(fields{k});
                case {'SystemResponse'}
                    % if valid, use new value
                    if isempty(metaData.(fields{k}))
                        metaData.(fields{k}) = oldMetaData.(fields{k});
                    end
                case {'nsec', 'ngaps', 'gaps'}
                    % we do NOT want this information updated, unless we
                    % just fixed a bug in the gap processing routine;
                    % in this case, temporarily comment out this line.
                    %metaData.(fields{k}) = oldMetaData.(fields{k});
                case {'system_errors','errors'}
                    % leave them alone
                otherwise
                    metaData.(fields{k}) = oldMetaData.(fields{k});
            end
        end
    end
end

% once everything else is updated, compute the IGRF declination
% Compute declination using IGRF and an open-source toolbox by Drew Compston
valid_date = datenum([metaData.startDate ' ' metaData.startTime]);
try
    map_elev = natmaplook(metaData.lat,metaData.lon);
catch
    if isnan(metaData.elev)
        map_elev = 0;
    else
        map_elev = metaData.elev;
    end
end

% The latest IGRF dat file is 2020-2025 dat file as of JWC 7/12/23
if (valid_date > datenum('2025-01-01'))
    valid_date = datenum('2025-01-01');
    warning('Declination computed as of 2025-01-01. May be off by decimals.');
end
B = igrf(valid_date,metaData.lat,metaData.lon,map_elev/1000.);
igrfdecl = rad2deg(atan2(B(2),B(1)));

% Document what we are doing here!
decl_info.igrf.version = 13;
decl_info.igrf.toolbox = 'igrf.m by Drew Compston';
decl_info.igrf_conf.date = datestr(valid_date,'yyyy-mm-dd');
decl_info.igrf_conf.lat = metaData.lat;
decl_info.igrf_conf.lon = metaData.lon;
decl_info.igrf_conf.elev = metaData.elev;
decl_info.file_decl = metaData.decl_info.file_decl;

% Let the user know if a pre-2020 NIMS was used and declination updated
if ~isnan(metaData.decl)
    disp(['NIMS file declination ' num2str(metaData.decl) ...
        ' replaced with IGRF declination ' num2str(igrfdecl) '. ']);
end
metaData.decl_info = decl_info;
metaData.decl = igrfdecl;

% finally, update the system response structure
if strcmp(metaData.InstrumentType,'NIMS')
    metaData.SystemResponse = NIMsysRsp(metaData.InstrumentID,HZ);
elseif strcmp(metaData.InstrumentType,'ZEN')
    metaData.SystemResponse = ZENsysRsp(metaData.InstrumentID,HZ);
end