IVS-EOP file format Version 3.0 (Jun 27, 2022) Claudia Flohrer, BKG (claudia.flohrer@bkg.bund.de) John Gipson, IVS Analysis Coordinator (john.m.gipson@nasa.gov) INTRODUCTION The IVS is using a dedicated IVS-EOP file format for distributing its EOP time series. The previous format version 2.2 (provided at the IVS AC webpage: https://ivscc.gsfc.nasa.gov/IVS_AC/files_IVS-AC/eop_transfer_format.txt) consists of a data block and optional comment lines. The information on the used nutation model was indicated by the file name extension only. Other relevant information, as e.g. the format version, AC, time window, reference frame, were not provided in a standardized format inside the EOP file. Therefore, this format version was updated to add relevant basic information on the EOP generation in a standardized format directly in the EOP file by using a dedicated header block with keywords. The new format description is inspired by the SINEX format description and makes use of a similar block structure. The changes from version 2.2 to 3.0 are given in the next section of this document. CHANGES FROM VERSION 2.2 TO 3.0 1) The character set to be used is defined being ASCII. 2) The naming convention of the file name is defined. 3) A first line as mandatory data description line (similar to SINEX format) is added. This line includes the specification of the used time scale. 4) A header block is added after the data description line and before the data block, containing keyword-based information. 5) A last line as mandatory footer line (similar to SINEX format) is added. 6) Two additional comment lines are added above the actual data lines, describing the data columns (column identifier and units) for better readability. 7) The units of the data field entries are no longer fixed but can be chosen. The units are indicated as part of the header keyword EOP_ESTIMATED. Valid unit values are specified in the format description. 8) The format of the data field entry for column 30 (network) has changed. The sequence of 2-character station identifiers is no longer directly attached to each other, but using '-' between each station identifier. 9) An additional data field 31 for comments is added. REFERENCES - IVS-EOP format version (2.2): https://ivscc.gsfc.nasa.gov/IVS_AC/files_IVS-AC/eop_transfer_format.txt - Proposal for extending the IVS-EOP 2.2 format: Proposal_EOPfileformat_v30.pdf - SINEX format description: https://www.iers.org/IERS/EN/Organization/AnalysisCoordinator/SinexFormat/ sinex.html ------------------------------------------------------------------------------- + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + ------------------------------------------------------------------------------- IVS-EOP file format Version 3.0 (Jun 27, 2022) A P P E N D I X I V S - E O P V E R S I O N 3. 0 D E T A I L F O R M A T D E S C R I P T I O N 1. INTRODUCTION 2. DATA STRUCTURE 3. DATA DESCRIPTION LINE 4. HEADER BLOCK 5. DATA BLOCK 6. FOOTER LINE 7. FILE NAME CONVENTION 1. Introduction This document describes the IVS-EOP format. The IVS is using a dedicated EOP format, to provide it's EOP estimates to the IERS Rapid Service/Prediction Centre, the IERS Earth Orientation Centre and to the scientific community. The IVS-EOP format was suggested by Leonid Petrov in 1999. In 2021, the IVS analysis working group accepted a proposal made by BKG for a format update from version 2.2 to version 3.0. This latest update of the format introduced a bigger change, by adding a dedicated header block with keywords, which give information in the underlying solution used to generate the reported EOP time series. We are thankful for feedback from the IVS community, and particularly want to acknowledge the comments of James Anderson and Leonid Petrov. 2. Data Structure An IVS-EOP file must start with a data description line and ends with a footer line. The file is subdivided into two blocks. Each block is enclosed by a header and trailer line. The following blocks are defined: HEADER DATA These block titles are immediately preceded by a '+' or a '-' marking the beginning and the end of a block. The block titles must be in capital letters. After a block has started(+) it must be ended(-) before another block can begin. The general structure is as follow: %=IVS-EOP... (Data description line)----+ ............. | +HEADER -------------+ | ............. | | ............. | | ............. | | -HEADER -------------+ | ............. | +DATA -------------+ | ............. | | ............. | | ............. | | -DATA -------------+ | ............. | %IVS-EOP...END (Footer line)----+ The DATA block comes after the HEADER block. Lines starting with '#', '*', '!' in column 1 are considered as comment lines. Comment lines are allowed everywhere, i.e. also within the header and data block. The IVS-EOP file is an ASCII file using the ASCII character set. 3. Data Description Line (Mandatory) Description: The data description line is mandatory and must be the first line in an IVS-EOP file. Contents: __________________________________________________________________________ |_____________D_A_T_A___D_E_S_C_R_I_P_T_I_O_N___L_I_N_E____________________| | | | | |__Field_________|__Description______________________|__Format_____________| | | | | | First Character| Single character '%' in column #1.| A1 | | | No other character than '%' is al-| | | | lowed. | | |________________|___________________________________|_____________________| | | | | | Second | Single character '=' in column #2.| A1 | | Character | Indicates resultant solution. No | | | | other character than '=' is al- | | | | lowed. | | |________________|___________________________________|_____________________| | | | | | Document Type | Seven characters 'IVS-EOP' | A7 | | | indicating that this is an IVS-EOP| | | | file. | | |________________|___________________________________|_____________________| | | | | | Format Version | Three digits indicating the format| 1X,F3.1 | | | version used. | | | | '3.0' for this version | | |________________|___________________________________|_____________________| | | | | | File Agency | Agency creating the file, e.g, | 1X,A3 | | Code | IVS for IVS combination center | | |________________|___________________________________|_____________________| | | | | | File Time | Creation time of this IVS-EOP file| 1X,I4,"-",I2,"-", | | | (YYYY-MM-DDTHH:MM:SS) | I2,"T",I2,":",I2, | | | | ":",I2 | |________________|___________________________________|_____________________| | | | | | Agency Code | Agency providing the data in the | 1X,A3 | | | file, e.g., BKG, which runs the | | | | IVS combination center | | |________________|___________________________________|_____________________| | | | | | Start Time | Start time of the data used in the| 1X,I4,"-",I2,"-", | | | file | I2,"T",I2,":",I2, | | | (YYYY-MM-DDTHH:MM:SS) | ":",I2 | |________________|___________________________________|_____________________| | | | | | End Time | End time of the data used in the | 1X,I4,"-",I2,"-", | | | file | I2,"T",I2,":",I2, | | | (YYYY-MM-DDTHH:MM:SS) | ":",I2 | |________________|___________________________________|_____________________| | | | | | Time scale | Three letters indicating the time | 1X,A3 | | | scale used | | |________________|___________________________________|_____________________| | | | | | Observation | Single character indicating the | 1X,A1 | | Code | technique(s) used to generate the | | | | EOP solution. It should be | | | | consistent with the IERS | | | | convention. This character code | | | | may be: | | | | C - combined techniques used | | | | D - DORIS | | | | L - SLR | | | | M - LLR | | | | P - GNSS | | | | R - VLBI | | |________________|___________________________________|_____________________| 4. HEADER block (Mandatory) Description: The header block is built of single lines for each keyword, starting with a keyword, followed by a value. Keywords can be mandatory or optional. The keyword values can be specific values from a given list (for machine readability) or free values (for information only). Contents: __________________________________________________________________________ |________________H_E_A_D_E_R___K_E_Y_W_O_R_D___L_I_N_E_____________________| | | | | |__Field_________|__Description______________________|__Format_____________| | | | | | Keyword | Keyword in free format, in capital| A, 1X | | | letters, no blanks are allowed in | | | | between words forming one keyword | | | | (use '_' instead). | | | | | | | | The keyword starts at the | | | | beginning of each line and is | | | | separated from the following value| | | | by a single ASCII character space.| | | | | | | | The list of allowed keyword is | | | | provided below. | | |________________|___________________________________|_____________________| | | | | | Value | Values may be preceded by extra | see below | | | ASCII spaces or ASCII tabs to aid | | | | forming readable columns. Values | | | | that contain lists must have the | | | | values separated by one or more | | | | ACSII spaces or ASCII tabs between| | | | each element of the list. | | | | | | | | Values use either a fixed format, | | | | tokens from a defined list or free| | | | format. The list of allowed values| | | | for each keyword is provided | | | | below. | | |________________|___________________________________|_____________________| List of allowed keywords and values: Most keywords are mandatory. Optional keywords are given in brackets in the table below. __________________________________________________________________________ | | | | |__Keyword_______|__Description__________________|__Value__________________| | | | | | GENERATION_TIME| Time of file generation | YYYY-MM-DDTHH:MM:SS | | | | | | | | I4,"-",I2,"-",I2,"T" | | | | I2,":",I2,":",I2 | |________________|_______________________________|_________________________| | | | | | DATA_START | Start of data | as above | |________________|_______________________________|_________________________| | | | | | DATA_END | End of data | as above | |________________|_______________________________|_________________________| | | | | | DESCRIPTION | Description of solution | free format | |________________|_______________________________|_________________________| | | | | | ANALYSIS_CENTER| IVS analysis center code | free format | |________________|_______________________________|_________________________| | | | | | CONTACT | IVS analysis center point of | free format | | | contact | | |________________|_______________________________|_________________________| | | | | | SOFTWARE | Software and version number | free format | | | used to generate the EOP | | | | solution | | |________________|_______________________________|_________________________| | | | | | TECHNIQUE | Observation technique(s) used | Choose one value | | | to generate the EOP solution | from list for single | | | | technique solution: | | | | | | | | V24 | | | | (VLBI R1/R4) | | | | VINT | | | | (VLBI Intensives) | | | | VGOS | | | | (VLBI VGOS sess.) | | | | VLBI | | | | (VLBI, if none of | | | | the above) | | | | GNSS | | | | SLR | | | | DORIS | | | | | | | | Combine individual | | | | codes with '+' to | | | | generate one value | | | | for combined sol- | | | | ution, e.g.: | | | | | | | | VINT+V24 | | | | VINT+V24+GNSS | | | | VINT+GNSS | | | | V24+GNSS+SLR | |________________|_______________________________|_________________________| | | | | | NUTATION_TYPE | Representation of nutation | Choose one value | | | | from list: | | | | | | | | EQUINOX-BASED | | | | CIO-BASED | |________________|_______________________________|_________________________| | | | | | ROTATION_TYPE | Representation of rotation | Choose one value | | | | from list: | | | | | | | | UT1-UTC_LOD | | | | UT1-TAI_LOD | |________________|_______________________________|_________________________| | | | | | CRF_APRIORI | A priori celestial reference | free format | | | frame | | |________________|_______________________________|_________________________| | | | | | TRF_APRIORI | A priori terrestrial reference| free format | | | frame | | |________________|_______________________________|_________________________| | | | | | EOP_SUBDAILY | Sub-daily pole model | Choose one value | | | | from list: | | | | | | | | IERS2010 | | | | DESAI-SIBOIS | | | | GIPSON | | | | NONE | |________________|_______________________________|_________________________| | | | | | EOP_APRIORI | A priori EOP | free format | |________________|_______________________________|_________________________| | | | | | EOP_ESTIMATED | One line for each estimated | Examples for | | | EOP, with values separated by | | | | one or more ASCII spaces or | offsets: | | | ASCII tabs, following the | XPOL 0.045 as | | | notation: | YPOL 0.045 as | | | | DUT1 0.003 s | | | NAME[_TIMEDEP_DEGREE] | DPSI NONE mas | | | CONSTRAINT UNIT [RHS] | DEPS NONE mas | | | | | | | with [] indicating optional | rates: | | | arguments | XPOL_DER_1 0.045 as/day | | | | YPOL_DER_1 0.045 as/day | | | NAME specifies the parameter | LOD 0.003 s | | | name. Valid names are: | DPSI_DER_1 NONE mas/day| | | | DEPS_DER_1 NONE mas/day| | | XPOL, YPOL, DUT1, LOD, | | | | DPSI or DX, DEPS or DY | piece-wise linear | | | | offsets: | | | TIMEDEP could be either | XPOL_BSP_1 0.045 as | | | | YPOL_BSP 1 0.045 as | | | DER (time derivative) or | DUT1_BSP_1 0.003 s | | | BSP (B-spline) | DPSI_BSP_1 NONE mas | | | | DEPS_BSP_1 NONE mas | | | DEGREE is the degree of the | | | | time derivative/B-spline. | | | | | | | | CONSTRAINT is the value for | | | | the constraint (i.e. the | | | | reciprocal weight) applied | | | | for the specific parameter. | | | | Use 'NONE' if no constraint | | | | was used. | | | | | | | | UNIT specifies the unit of the| | | | EOP estimates and of the | | | | corresponding constraint | | | | (both units have to be the | | | | same). Valid units are: | | | | | | | | s - second | | | | ms - millisecond | | | | us - microsecond | | | | | | | | as - arcsecond | | | | mas - milliarcsecond | | | | uas - microarcsecond | | | | | | | | /day - each unit above/day | | | | | | | | RHS specified the right hand | | | | side value. | | | | | | | | EOP, which are not estimated, | | | | should not be specified here. | | | | EOP can appear in random | | | | order. | | | | | | | | Note: LOD is treated here as | | | | individual parameter and not | | | | as dUT1 derivative. It is | | | | maintained with the group of | | | | rates for consistency with the| | | | other techniques. | | |________________|_______________________________|_________________________| | | | | | [NUMBER_OF_ | Total number of entries (data | Integer number | | ENTRIES] | lines) in the data block | | |________________|_______________________________|_________________________| 5. DATA block (Mandatory) Description: The data block is built of single lines per epoch. Two additional comment lines, with the first line describing the data field and the second line describing the units, are placed immediately before the first data line. For readability the values in these two comment lines should be placed centered over the columns. The values of the first description line have to correspond to the identifier given in the 2nd column of Table 4, but all values are case insensitive. The units have to be consistent with the units described in the header block (keyword UNIT). They can differ from the example given in the DATA LINE table below (3rd column). Consult the keyword table above (Sec. 4) for valid units. All data records have to be ordered in time. The lines of the data block are free format, allowing for a variable field length. The fields are separated by at least one ASCII space. The lines should be parsed by splitting on whitespaces rather than using hard-coded field widths. There are 31 data fields (columns) per line. Data which is unavailable is replaced by NA. This is the case for example with Intensives, which don’t estimate polar motion, nutation, or EOP rates. Several data entries (i.e. lines) per parameter and session are possible, depending on the EOP parameterization, e.g., high resolution of offsets (every hour) or piece-wise linear offsets. Contents: __________________________________________________________________________ |_____________________________D_A_T_A___L_I_N_E____________________________| | | | | | | |Field| 1st line | 2nd line| | Number of min.| |_No._|_Identifier_|__Unit___|__Description________________|_decimal_digits| | | | | | | | 1 | epoch | [MJD] | Decimal MJD of measurements | 5 | |_____|____________|_________|_____________________________|_______________| | | | | | | | 2 | xPol | [as] | x component of the pole | 7 for [as] | |_____|____________|_________|_____________________________|_______________| | | | | | | | 3 | yPol | [as] | y component of the pole | 7 for [as] | |_____|____________|_________|_____________________________|_______________| | | | | | | | 4 | dUT1 | [s] | UT1-UTC or UT1R-UTC or | 8 for [s] | | | | | UT1-TAI or UT1R-TAI | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 5 | dPsi or | [mas] | Nutation component dPsi or | 4 for [mas] | | | dX | | dX | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 6 | dEps or | [mas] | Nutation component dEps or | 4 for [mas] | | | dY | | dY | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 7 | sig_xP | [as] | Uncertainty in x pole | 7 for [as] | |_____|____________|_________|_____________________________|_______________| | | | | | | | 8 | sig_yP | [as] | Uncertainty in y pole | 7 for [as] | |_____|____________|_________|_____________________________|_______________| | | | | | | | 9 | sig_UT | [s] | Uncertainty in UT1-UTC or | 8 for [s] | | | | | UT1-TAI | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 10 | sig_dPsi or| [mas] | Uncertainty in nutation | 4 for [mas] | | | sig_dX | | component dPsi or dX | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 11 | sig_dEps or| [mas] | Uncertainty in nutation | 4 for [mas] | | | sig_dY | | component dEps or dY | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 12 | wRMS | [ps] | WRMS residual delay of the | 1 for [ps] | | | | | session | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 13 | cor_xPyP | [-] | Correlation coefficient: | | | | | | xPol, yPol | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 14 | cor_xPUT | [-] | Correlation coefficient: | | | | | | xPol, dUT1 | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 15 | cor_yPUT | [-] | Correlation coefficient: | | | | | | yPol, dUT1 | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 16 | cor_dPdE or| [-] | Correlation coefficient: | | | | cor_dXdY | | dPsi, dEps or dX, dY | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 17 | nObs | [-] | Number of observables used | | | | | | for deriving reported EOP or| | | | | | '0' for a global solution. | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 18 | sessID | [-] | 6-character session code | | | | | | according to the 2nd column | | | | | | of IVS master schedules | | | | | | | | | | | | Use the key 'COMBINED' for | | | | | | combined sessions or | | | | | | techniques. | | | | | | | | | | | | Use the key 'GLOBAL' for a | | | | | | global solution. | | | | | | | | | | | | Note: The current | | | | | | 6-character session code | | | | | | might, in the future, change| | | | | | to at least 32 characters. | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 19 | span | [h] | Span of the observation used| | | | | | for deriving reported EOP or| | | | | | '0' for a global solution. | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 20 | xPolR | [as/day]| Rate of the x pole component| 8 for [as/day]| |_____|____________|_________|_____________________________|_______________| | | | | | | | 21 | yPolR | [as/day]| Rate of the y pole component| 8 for [as/day]| |_____|____________|_________|_____________________________|_______________| | | | | | | | 22 | LOD | [s] | Excess length of day | 9 for [s] | | | | | | | | | | | Note: see comment below | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 23 | dPsiR or |[mas/day]| Rate of the nutation | 5 for | | | dXR | | component dPsi or dX | [mas/day] | |_____|____________|_________|_____________________________|_______________| | | | | | | | 24 | dEpsR or |[mas/day]| Rate of the nutation | 5 for | | | dYR | | component dEps or dY | [mas/day] | |_____|____________|_________|_____________________________|_______________| | | | | | | | 25 | sig_xPR | [as/day]| Uncertainty in x pole rate | 8 for [as/day]| |_____|____________|_________|_____________________________|_______________| | | | | | | | 26 | sig_yPR | [as/day]| Uncertainty in y pole rate | 8 for [as/day]| |_____|____________|_________|_____________________________|_______________| | | | | | | | 27 | sig_LOD | [s] | Uncertainty in LOD | 9 for [s] | |_____|____________|_________|_____________________________|_______________| | | | | | | | 28 | sig_dPR or |[mas/day]| Uncertainty in rate of the | 5 for | | | sig_dXR | | nutation component dPsi or | [mas/day] | | | | | dX | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 29 | sig_dER or |[mas/day]| Uncertainty in rate of the | 5 for | | | sig_dYR | | nutation component dEps or | [mas/day] | | | | | dY | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 30 | network | [-] | Configuration of network | | | | | | employed for the solution: | | | | | | sequence of 2-character IVS | | | | | | station identifiers as | | | | | | maintained in the IVS master| | | | | | control file ns-codes.txt | | | | | | with '-' between the | | | | | | station codes (no blanks) | | | | | | | | | | | | Example: Ts-Wz-Ny | | | | | | | | | | | | Use the key 'COMBINED' for | | | | | | combined sessions or | | | | | | techniques. | | | | | | | | | | | | Use the key 'GLOBAL' for a | | | | | | global solution. | | |_____|____________|_________|_____________________________|_______________| | | | | | | | 31 | comments | [-] | Comment field, could be used| | | | | | for any additional informat-| | | | | | ion, e.g. session specific | | | | | | constraints, details on | | | | | | combined sessions. | | | | | | | | | | | | Entry has to start with a | | | | | | leading '!' | | |_____|____________|_________|_____________________________|_______________| Comment: Although it is inconsistent to have LOD in the group of rates due to the toggling of the sign, it is maintained here for consistency with the other space-geodetic techniques. LOD = UT1(n)-UT1(n+1) with n in days LOD has the same magnitude but opposite sign of the UT1-UTC rate or the UT1-TAI rate, which are normally determined in VLBI analyses and given in s/day. 6. Footer Line (Mandatory) Description: The footer line is mandatory and must be the last line in an IVS-EOP file. Contents: __________________________________________________________________________ |__________________________F_O_O_T_E_R___L_I_N_E___________________________| | | | | |__Field_________|__Description______________________|__Format_____________| | | | | | First Character| Single character '%' in column #1.| A1 | | | No other character than '%' is al-| | | | lowed. | | |________________|___________________________________|_____________________| | | | | | Document Type | Seven characters 'IVS-EOP' | A7 | | | indicating that this is an IVS-EOP| | | | file. | | |________________|___________________________________|_____________________| | | | | | Format Version | Three digits indicating the format| 1X,F3.1 | | | version used. | | | | '3.0' for this version. | | |________________|___________________________________|_____________________| | | | | | End | Last 3 characters 'END' marking | 1X,A3 | | | the end of the file. | | |________________|___________________________________|_____________________| 7. File name convention The IVS-EOP file name follows the file name convention as given at: https://ivscc.gsfc.nasa.gov/products-data/submit-product.html There are three file types with different extensions: __________________________________________________________________________ | | | | |__File_type____|__Naming_convention__|__Comment___________________________| | | | | | EOP-I results | aaaccccc.eopi | Intensives EOP series (without | | | | nutation offsets) | |_______________|_____________________|____________________________________| | | | | | EOP-S results | aaaccccc.eops | Session EOP series (with nutation | | (IAU1980) | | offsets referring to the IAU1980 | | | | model) | |_______________|_____________________|____________________________________| | | | | | EOP-S results | aaaccccc.eoxy | Session EOP series (with nutation | | (IAU2000) | | offsets referring to the IAU2000 | | | | model) | |_______________|_____________________|____________________________________| The following keys are used: - aaa = Analysis Center 3-letter code - ccccc = Solution 5-character code