NOWOŚĆ
TOP (Trimble Online Processing)
APPS (Automatic Postprocessing Software)
The POZGEO website is intended for post-processing calculations of GPS observations made using the static method. Phase observations from single- and dual-frequency receivers, converted to a fixed observation data format, are used for calculations. Access to the website is provided via the system website: system.asgeupos.pl. After logging in, the user can send observation data using the prepared submission form. After uploading the observation file, it is checked for correctness of the format and then transferred to the automatic postprocessing application implemented through Automatic Postprocessing Software for Trimble Application (APPS). The software performs calculations based on double differences of phase observations. An additional feature of the software is the use of absolute calibrations for GPS antennas. Calculations for the sent observation files are performed based on the 6 nearest reference stations, for which the designated vectors meet certain accuracy criteria. On their basis, alignment is performed, resulting in station coordinates in the ETRF2000 (European Terrestrial Reference Frame) system. Additionally, the coordinates are converted to the 2000, 1992 and 1965 systems. Depending on the date of entering the observation file, navigation orbits, IGS-rapid or IGS-final are used for calculations. Since the POZGEO service is an automatic service, please verify whether the name of the antenna model given in the RINEX file header is consistent with its designation in the igs08.atx file. Otherwise, the antenna phase center model will not be taken into account in the calculations. Calculations in the POZGEO website are performed for observation files that meet the following criteria:
Data format
Observations from GNSS systems should be saved in the RINEX v2.x format (Receiver Independent Exchange Format). The system only uses observation files (extension e.g. 24o – for 2024). The POZGEO website does not accept files in the RINEX v3 format, as well as navigation and meteorological files. In order for the file to be recognized well by the system, it is important that the RINEX file header contains the following entries:
RINEX VERSION / TYPE
PGM / RUN BY / DATE
MARKER NAME
OBSERVER / AGENCY
REC # / TYPE / VERS
ANT # / TYPE
APPROX POSITION XYZ
ANTENNA: DELTA H/E/N
WAVELENGHT FACT L1/2
# / TYPES OF OBSERV
INTERVAL (wpis opcjonalny, zaleca się jego stosowanie)
TIME OF FIRST OBS
TIME OF LAST OBS (wpis opcjonalny, zaleca się jego stosowanie)
END OF HEADER
After completing the header, the next entry should be the definition of the observation epoch, e.g.: 08 06 24 12 05 30.000000 0 4G07G08G10G13 The height of the antenna in the RINEX file (entered in the ANTENNA: DELTA H/E/N line) should be related to the ARP point (Antenna Reference Point). This point is usually referred to as the bottom of the antenna mounting.
Here You can find the specification of RINEX standards: https://igs.org/formats-and-standards/
Number of satellites
Calculations in the POZGEO website are performed for static observations made simultaneously of up to 4 GPS satellites. This is the minimum resulting from the mathematical problem of determining the position in the GPS system (determining the XYZ coordinates and time corrections for the receiver clock). The recommended number of satellites for this service should be greater than or equal to 5.
File size
The maximum file size that can be sent for calculations is 17 MB. To reduce size, observation files can be limited to observations C1, P1, P2, L1, L2. Only such signals are taken into account for calculations.
Observation period
Observation files submitted for calculation should be longer than 15 minutes and shorter than 24 hours. However, they must meet additional conditions regarding the number of registered measurement epochs. Since POZGEO is an automatic service, it is recommended that observation files sent for POZGEO calculations contain at least 40 minutes of 1-second dual-frequency GPS phase observations. Otherwise, the accuracy of the calculations cannot be guaranteed. Only observations to satellites located above 10 degrees above the horizon are included in the observation time. The minimum number of epochs for which calculations are performed is 720 (e.g. 15 minutes of observation with an interval of 1 second). Observation files that do not meet this condition are automatically rejected. Maximum number of epochs used: 3600 (e.g. 1 hour of observation with an interval of 1 second). If this value is exceeded, observations are diluted to a smaller interval that is a multiple of the base format (e.g. from an interval of 5 seconds to 10 seconds).