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First, how do the times synchronize between the in-situ data, the ITT data, and the navigation information? The times of the data acquisition computers are supposed to be synchronized before each flight. In practice this is sometimes omitted. What I have done in the past is to compare the ITT and the LaRC gps files and find the time the aircraft takes off in each one. I then adjusted the LaRC time so that takeoff occurs in the LaRC file at the same time as in the ITT file. The difference in time has been from 0 to 77 seconds, usually just a few seconds. I need to do this because I must assign altitudes from the gps file to the in situ co2 values. It may not be necessary for your application. Second, could you please provide additional information regarding the file structure of the ITT data? I’ve attached an updated document for ITT data formats – look at the “CO2” tab. Unfortunately this data format has changed several times over the years and it changed between flights 2 and 3 in October. I suggest you start with flight 3. If you look in the idl module updatin.pro the data stream is explained. You have 9 64-bit values per line, or 9 columns of data. The first is a time stamp generated by either LabView or Matlab. Items 2-5 are reference signal values. Items 6-9 are return signal values. So you need to convert the time stamp to GMT or local time for the flight location. If you look at the first_leg*.gif files in sample plots on the DVD you will see time series of reference and return or “science” signals for one file of flight 3. Third, of what are the negative altimeter readings in the in-situ data indicative? The LaRC gps altimeter was giving negative values but these are within the measurement accuracy of the instrument. I adjusted them so that the average altitude before takeoff matched that of the Newport New airport. ITT’s gps instrument appeared to be more accurate. <a href="http://spreadsheets.google.com/pub?key=pN6N2arOWoYVaFc8HXfAIfA">Attachment</a> 2008-07-01T15:26:35-07:00 32286 answers

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2008-07-02T12:04:36-07:00

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