Archive for 2008

SAC helping the ESA/ESOC GPS Reprocessing

Saturday, November 29th, 2008

Vapor de Agua sobre Observatorio Roque de los Muchachos (LPAL)

Saturday, September 27th, 2008

What is EGNOS?

Saturday, August 23rd, 2008

IGS reprocessing, an exciting project!

Sunday, July 13th, 2008

After the IGS workshop which we recently concluded to great success, one of the most important and interesting activities for the near future is the reprocessing of all the historical IGS data using current state-of-the-art techniques.

Reprocessing of GPS data back to 1994 is a high-priority of the IGS since modern techniques can better estimate the IGS products of the past. The original products produced week to week continue to be the “gold standard” of GPS precision as they are store in Data Centers around the world. These products can be used by scientist, engineers and researchers as the best GPS orbit, clocks and ITRF values for their own research and post-processing. The reasons for the urgent need for reprocessing all of the IGS products are as follows:

  1. The IGS is now using absolute Antenna Phase Center calibrations for ground and space antennas (ANTEX), this has brought the IGS ITRF station position estimations closer to other techniques and reduced uncertainty. This jump introduced in GPS week 1400 (Nov, 2006) creates a discontinuity with the previous IGS products, which needs to be removed by reprocessing the older data with the new standards.
  2. The IGS product consistency and accuracy has improved over time as better processing methods and standards have been implemented at each of the Analysis Centers. This high-level of consistency and increased accuracy which now exists needs to be extended backwards in time for the benefit of all. With more precise past products better science can be produced by the users of the IGS products.
  3. The IGS has adopted many reference frame updates as the ITRF reference frame has been updated over time. This creates a set of products that is not continuous over time as each new ITRF realization introduces a new set of precise coordinates and velocities for the stations. The reprocessing will produce a consistent set of products using the latest ITRF05 reference frame.
  4. Data processing limitations of the past are removed. As computer speed and power has increased , it is now possible to include many more stations as available in the reprocessing of the IGS products. The inclusion of more data for the reprocessing allows for better products and for many more reference station coordinates to be estimated precisely.

The improvement of the IGS products over time can be best highlighted by the IGS Analysis Center Coordinator orbit quality plot:

IGS Final Orbits from each AC since the IGS start

IGS Final Orbits from each AC since the IGS start

The justification for the IGS reprocessing are therefore clear, and most of the IGS Analysis Centers have committed time and resources to contribute to this effort to reprocess the data for the time period between 01/1994 to 12/2007. The reprocessing efforts are being coordinated by the IGS ACC from this website which I encourage anyone interested to visit: ACC Reprocessing website.

The main output, apart from the much improved GPS products, will be the station positions to be used in the next realization of the International Terrestrial Reference Frame (ITRF).

Take care
Nacho Romero

The CGC Station Information System

Wednesday, June 18th, 2008

CGC Station System – Manual de Uso

IGS Workshop 2008 Contents & Summary

Monday, June 9th, 2008

  1. Incorporating the 2nd and 3rd order iono corrections to the GPS processing
  2. Correlating antenna monuments with problems in our ESA IGS processing
  3. Participating in the incipient IGS Infrastructure Committee
  4. Learning more about the albedo/infrared implementation to resolve the SLR residual issues in the GPS processing

The IGS Workshop 2008

Monday, June 2nd, 2008

Datos GNSS libres y abiertos de España

Wednesday, May 21st, 2008

Data Policy – Política de Datos

Saturday, April 26th, 2008

Política de Datos es la especificación clara y por escrito por la institución que instala una estación permanente GNSS para que los datos recabados sean de dominio público en algun momento. Especificando un tiempo determinado para acceder a los datos es fundamental para que los datos, que normalmente se han pagado por todos los contribuyentes, sean accessibles a todos en igualdad de condiciones.

Actualmente existen muchas estaciones GPS permanentes en Canarias y Africa que simplemente NUNCA ofrecen sus datos a la comunidad científico/técnica. Esto no es positivo para el avance de los estudios de nuestra región y sólo sirve para que varios organismos terminen duplicando esfuerzos con recursos limitados lo cual es un despilfarro.

Lo más importante para cualquier organización que instale un equipo permanente GNSS (GPS o GPS+GLONASS, etc), o cualquier otro equipo científico, es institutir una “Política de Datos” que sea pública y clara para que todos sepamos cuanto tenemos que esperar por esos datos (1 seg, 1 dia, 1 semana, 1 mes, 1 año), pero NUNCA es inaceptable. Esos datos serán beneficiosos para estudios y analisis a largo plazo y si nunca se hacen públicos corren el serio riesgo de perderse por olvido o error.

Una vez que se tenga una Política de Datos” hay que cumplirla! y dar los datos libremente a todos sin ningún tipo de traba ni cortapisas. Para esto lo mejor es publicarlos en servidores de datos globales y regionales como SIO, CDDIS, CGC, EUREF, etc, y anuncuar este echo en comunicaciones oficiales y en las webs pertinentes.

Si tiene cualquier duda al leer esto o le sugiere alguna idea adicional por favor contacteme y ayudenme a cambiar la forma de pensar de tantos investigadores que trabajan en nuestra region! Gracias.

Data Policy with respect to permanent GNSS installations is a very critical issue. I generally work in the IGS context which has an “open data policy” and also an “open product policy”.

It is easy to assume that since the IGS has 300+ permanent GNSS stations from dozens of organizations we have “won this battle” but nothing is further from the truth. In fact more data is hidden than open especially in areas with difficulties for permanent installations. We have recently discovered many GPS stations in the Canary Islands which never make their data public, the same is true for many stations in the African continent. This seems unacceptable and should change.

Considering that all these stations belong to public institutions which are paid with tax payer’s money this hidding of data seems incorrect. All organisations that decide to invest in GNSS stations should have a publicly available “Data Policy” so that after a certain amount of time the data is “opened” for free access to all. This could be 1 second, 1 hour, 1 week, 1 month, 1 year or whatever. What is reasonable is to have a Data Policy so that all the data is available “at some point” for long term scientific studies to all members of the scientific community in an open and uncomplicated download method (CDDIS, SIO, EUREF, CGC, etc).

Estaciones GNSS en Canarias

Tuesday, March 25th, 2008