Web 1:5000 - Gipuzkoa Provincial Council

http://www.autognss.com

AutoGNSSis a free online GPS vector processing service based on static observations. The data collected by a dual frequency receptor are sent in Rinex format to a server, which processes the data by linking them to Gipuzkoa GPS Network and nearby IGS stations. The reference frame is Gipuzkoa GPS Network if the time spam is less than 4 hours and is located less than 60 km from this network. Otherwise, the framework is exclusively IGS. The solutions are offered in both IGS framework and ETRS89. The application sends an email to the user indicating observed incidents and a PDF with the solutions obtained. Centimetric solutions are expected depending on the quality of the data submitted by the user.

The application has been developed based on the National Geodetic Survey's Pages software and other freeware. The aim is to offer the user a comfortable and precise GNSS vector processing tool, and to enable the Gipuzkoa Provincial Council having an uniform surveying control utility.

If you have any queries or wish to integrate other GNSS stations in the application do not hesitate to contact us.

AutoGNSS. How does it work?

The user enters the observation data and e-mail address (together with additional comments, if any), and will receive an e-mail with the solution or detected errors, where applicable. Access to the application is done through a website; this limitation derives from the fact that the majority of users do not have ftp access.

The application only accepts dual frequency observation files in RINEX format (version 2.1. or above) or files with a ZIP extension containing one or more compressed RINEX files. The application accepts sampling intervals of 5, 10, 15 or 30 seconds, always referring to the same day.

Once the file has been received, the application will perform the following steps:

  • Check that the format of the observations is a valid Rinex file.
  • Calculate a centroid, sampling intervals and time spam of observations.
  • The closests suitable GPS stations are determined (Gipuzkoa and IGS). In case the observations are outside Gipuzkoa, only IGS Frame will be considered and the observations will be resampled to 30 seconds.
  • The observations of the GPS stations (Gipuzkoa and IGS) and the IGS ephemeris, IGS, IGR and IGU, in this order of availability, are downloaded.
  • Absolute Phase Center Variation will be used. In case the PCV is unknown for an antenna, ensure to contact us to add it to our database
  • The observations are synchronised and the initial solutions are improved by applying a triple differences model.
  • The vectors that form the minimum spanning tree are determined. The user station (or stations) is processed from the nearest GPS station.
  • The cycle slips and reference satellites for double differences are determined and the quality of the points is checked.
  • Each vector is independently determined.
  • The processed vectors are combined in a single solution.
  • Output reports and process summaries are created.
  • The results are sent to the user.

The most important parameters for the processing of vectors are (March 2006):

  • Dual frequency GPS observations
  • Elevation Mask: 15? (10? for observations < 4 hours)
  • Sampling Interval: 30 s for observations of over 3 hours duration or 1, 5, 10 or 15, according to the user’s data
  • Frequency: L3
  • Ionosphere: L3 combination.
  • Troposphere: Niell Mapping Function and Saastamoinen models combined. Zenith Tropospheric Delays estimated every 3 hours.
  • Terrestrial Tide Model: IERS
  • Oceanic Charge Model from IGS stations.
  • Correlated Double Differences

AutoGNSS. Relevant links

B5m.gipuzkoa.net home page.
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