{"id":23632,"date":"2022-04-01T10:18:57","date_gmt":"2022-04-01T09:18:57","guid":{"rendered":"https:\/\/reseau-orpheon.fr\/the-orpheon-network\/referencing-and-external-control-of-the-network\/"},"modified":"2022-04-06T13:19:27","modified_gmt":"2022-04-06T12:19:27","slug":"referencing-and-external-control-of-the-network","status":"publish","type":"page","link":"https:\/\/reseau-orpheon.fr\/en\/the-orpheon-network\/referencing-and-external-control-of-the-network\/","title":{"rendered":"Referencing and external control of the network"},"content":{"rendered":"\t\t
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For the highest quality of your measurements<\/h3>\r\nEach of the reception sites for the reference stations in the Orph\u00e9on network is selected with the greatest care and must respect criteria allowing stability and the best reception of satellite signals. The buildings on which the antenna masts are stowed were selected primarily on the basis of stability criteria.\r\n\r\nThe antenna masts are designed (diameter and thickness of sheets) to ensure subcentimetric stability of the phase center of the antenna, under all usual weather conditions (dilation under the effect of temperature and vibration under the effect of wind).\r\n

\"\"\u00a9 Leica CrossCheck<\/p>\r\n\r\n

Stationing procedure<\/h2>\r\nAfter the final installation of a reference station on a new site or after maintenance, we obtain a first approximate position of this site by observations over a minimum period of 72 hours. This duration makes it possible to obtain the first coordinates of the site.\r\n\r\nThen these observations are conducted over a month in order to acquire the time series which will be used to calculate the position thanks to the Leica CrossCheck Solution (service for calculating the coordinates of the GNSS reference station and monitoring the integrity of the network) and Bernese GNSS software (high-precision scientific multi-GNSS data processing software developed at the Astronomical Institute of the University of Bern (AIUB).\r\n\r\nLeica Geosystems experts process this geodetic GNSS data to provide high-precision estimates of the positioning and movements of each of the sites making up the Orpheon network.\r\n

Referencing<\/h2>\r\nAll the sites are referenced in the RGF93 via a “state of the art” procedure from the stations of the RGP (Permanent GNSS Network).\r\n\r\nThe RGF93 is a national reference:\r\n
    \r\n \t
  1. three-dimensional geocentric<\/li>\r\n \t
  2. linked to the global ITRS reference system<\/li>\r\n \t
  3. associated with the IAG GRS 1980 spheroid<\/li>\r\n \t
  4. having as its prime meridian the International Meridian (or Greenwich Meridian)<\/li>\r\n \t
  5. having as associated projections the Lambert-93 projection and the CC 9 Zones projections<\/li>\r\n \t
  6. horizontal accuracy between 1 and 2 cm (compared to global systems)<\/li>\r\n \t
  7. vertical accuracy between 2 and 5 cm (compared to global systems)<\/li>\r\n \t
  8. suitable for modern positioning techniques<\/li>\r\n<\/ol>\r\n

    We then obtain the position and the precise three-dimensional coordinates of the site which we can then integrate into the network to deliver the correction services.<\/p>\r\n\r\n

    LAMBERT parameters and Geoid model<\/h2>\r\nIn metropolitan and continental France, the legal geodetic system is RGF93v2b which is aligned with ETRF2000 epoch 2019.0.\r\n\r\nAll of our station coordinates are defined in this system. The associated ellipsoid is GRS80.\r\n\r\nThe legal projection is the Lambert 93 9 zone conformal conic projection. Each of these zones covers a latitude band of 2\u00b0. The titles of the 9 zones are:\r\nCC42\/CC43\/CC44\/CC45\/CC46\/CC47\/CC48\/CC49\/CC50. “CC” for conformal conic followed by the value of the zone’s central parallel. For example, CC48 covers a band in latitude going from parallel 47\u00b0N to parallel 49\u00b0N. The definition of these 9 zones ensures an overlap of 1\u00b0 between each zone.\r\n\r\nThe parameters of these projections are:\r\n\r\n– Origin latitude: 42\/43\/…\/50 depending on the area considered\r\n– Automecoic parallel 1: Origin latitude – 0.75\u00b0\r\n– Automecoic parallel 2: Origin latitude + 0.75\u00b0\r\n– Prime meridian: 3\u00b0E\r\n– Origin coordinates: 1,700,000 E; (1,000,000 x (origin latitude – 41\u00b0)) + 200,000 N\r\n\r\nIn terms of altimetry, the legal system is IGN69, for mainland France, the RAF20 altimetric conversion surface was updated at the end of 2021 to take into account the maintenance operations of the RGF93 reference mark.\r\n\r\nSince the summer of 2021, you can therefore download this new ‘grid’ from the IGN website (https:\/\/geodesie.ign.fr) which takes into account both the evolution of the RGF93 benchmark (ETRF2000 ep.2019.0) and the last two ERNIT field campaigns 2019 and 2020 in mainland France. IGN is also trying to improve the model at each occurrence by introducing some minor corrections from reports or redeterminations caused by local tectonic activity.\r\n\r\nFor mainland France, the RAF20 altimetric conversion surface was updated at the end of 2021 to take into account the maintenance operations of the RGF93 reference mark\r\n