Question

Hi again,

I wishing to clarify the definition for the column 'Estimate' in the DDRFileOutput of DDBase.

Estimate is the output from the DDBase LSQ estimation process (also known as post-fit)... and it is an estimation of the... ? (double difference - or are there other corrections applied?)

smile

To summarise my limited knowledge :):

DDRFileOut: RES .... Data .... Estimate .... Residual

RDDFileOut: RDD .... DDL1_m .... DDER_m .... resL1_m

I understand:

Data (DDRFileOut) = DDL1_m (RDDFileOut)

And that in each case the residual is the difference between the observed data and the estimation (or true range in the case for RDDFileOut).

Thanks smile

Michael

ps. Sorry if this may seen trivial. I just need to make sure 100% of what I'm writing about smile

-- MichaelRigby - 14 Nov 2007

Answer

ALERT! If you answer a question - or have a question you asked answered by someone - please remember to edit the page and set the status to answered. The status is in a drop-down list below the edit box.

Each of these output files includes one or more header rows describing the file format and contents. This header starts with a “title” line that begins with the ‘#’ character and contains the DDBase version number, and the date and time at which the file was created. This is followed by one or two lines that begin with the unique 3-character tag (RDD, DDR, etc.), followed by column labels. These labels should be somewhat self-explanatory. After these header lines, the data consists of the same form: one line per epoch, always beginning a unique 3-letter tag, often including the one that appears in the –-XXXFileOut option. Specific information on some of the files follows. The RDD output file contains the raw double differenced data. Double differences are of the form (site1,sat1)-(site2,sat1)-(site2,sat1)+(site2,sat2). Each line RDD consists of the following, separated by spaces. 1.‘RDD’ the tag, 2.the first site ID, 3.the second site ID, 4.the first satellite ID, 5.the reference (second) satellite ID, 6.the GPS week number, 7.the GPS seconds of week, 8.a quality flag (0 means good), 9.the double difference of L1 phase in meters, 10.the double difference of L2 phase in meters, 11.the double difference range predicted by the ephemeris in meters, 12.the difference of 9 and 11, and 13.the difference of 10 and 12. If dual frequency data is being processed, then there is a column 14.the wide lane bias in meters.

The RDD file also contains raw triple differences, using the tag ‘RTD’. Triple differences are double differences (the RDD data) differenced over with the same data from the previous epoch. These lines consist of 1.‘RTD’ the tag, 2-8 as with RDD, 9.the triple difference of L1 phase in meters, 10.the triple difference of L2 phase in meters, 11.the triple difference of the predicted ephemeris range in meters.

The DDR file is written from within the estimation part of the algorithm, and includes information on the post-fit residuals. The tag in this file is ‘RES’, and the columns consist of 1.’RES’ the tag, 2.the first site ID, 3.the second site ID, 4.the first satellite ID, 5.the reference (second) satellite ID, 6.the GPS week number, 7.the GPS seconds of week, 8.an integer count of timesteps, 9.the double difference data, in meters, that was used in the estimation, 10.the estimate of column 9 that DDBase produced, in meters, and 11.the difference of 9 and 10 in meters. It should be clear from the input which phase is used in column 9 : L1, L2 or the ionosphere-free combination.

-- BrianTolman - 14 Nov 2007

Thank you for your very comprehensive explaination. It has been very helpful smile And I should add that the help you provided has been perfect - thank you.

Cheers,

Michael

Topic revision: r8 - 12 Jun 2015, UnknownUser
 

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