2020-12-20 17:55:47
The preparation of the CienciaEs podcasts requires a lot of dedication time, generally sitting in front of the computer, and I go jogging around the studio at least once a day to stretch my legs. Since sport is not at odds with the fans, I always wear a watch that, in addition to allowing me to listen to other podcasts while I exercise, monitors my route at all times thanks to the connection GPS that it incorporates. Thus, when I return, I know with remarkable accuracy the path followed and the time spent in traversing it. This effort to know my position at all times also helps me when I travel with my vehicle through the city to go to record an interview. I never get lost because on my mobile phone I have information about where I am and the way to go thanks to an application that uses global positioning systems. And, at night, when the weather allows it, I usually observe the firmament with my telescope, a telescope that thanks to the GPS built-in, it knows its position with remarkable accuracy and, from it, it allows me to locate astronomical objects comfortably. These few examples are enough to illustrate to what extent my life has changed and I imagine yours too, thanks to modern positioning systems.
Today we are dedicating the program to high-precision positioning systems, that is, those that go beyond everyday applications and are essential in fields such as agriculture, civil engineering, topography, volcanology, and many other scientific and commercial activities. If the systems in general use provide information about the position with an accuracy of a few meters, which our guest explains to us today in Speaking with Scientists, Jose Antonio Sanchez Sobrinoengineer in Geodesy and Cartography of the National Geographic Institute
, allow to know the position with a precision of a few millimeters. This is achieved with the GNSSacronyms that derive from its English name “Global Navigation Satellite System”.
The modern positioning revolution began with the GPS, a set of 24 satellites that orbit at an altitude of more than 20,000 km, whose orbits are designed in such a way that any person on the Earth’s surface can always have several of them transiting above. Each satellite carries a very precise atomic clock and emits a signal that a receiver on the ground can perceive and use to calculate its position to an accuracy of a few meters. To the GPSinitially conceived for military purposes, other constellations have been added, such as the European one GALILEOthe Russian GLONASS or the china Beidou. However, despite their enormous achievement, the accuracy provided by satellite networks may be insufficient for certain applications. José Antonio Sánchez Sobrino explains that the electromagnetic signals sent by satellite networks have to pass through the Earth’s atmosphere to reach the receiver and suffer variations due to changes in density and composition of the ionosphere and troposphere. These changes result in inaccuracies in the position that can be improved if additional systems are used to correct errors. To achieve higher precision, of the order of centimeters or millimeters, in addition to the satellite constellations, a set of permanent geodetic stations distributed throughout the territory are used, whose position is known with great precision.
Currently the IGN It has about 120 permanent stations evenly distributed throughout the national territory. Of course, this set participates in broader networks that cover European and global territories. So the system GNSS It allows the error of the signal transmitted by the satellites to be calculated at all times and makes it easier for users who have adequate equipment to make the corrections that they must apply to obtain a much more precise positioning.
The applications of GNSS They cover many fields of knowledge. One of those fields is geodynamics, that is, the branch of knowledge that studies the internal and external movements of the Earth. Thanks to GNSS it is possible to monitor the movements of the tectonic plates, the variations of the terrain due to seismic movements, the processes that modify the elevation or subsidence of the soil, etc. Another field of application is meteorology. Since the signals from the positioning satellites must pass through the atmosphere and are affected by its variations, the received signal provides useful information on water vapor content and other useful data for weather forecasting services. The study of the changes caused by Climate Change, such as the variation in the average sea level, also benefit from the data provided by the GNSS. Added to these applications are those whose field of action is human activities that require knowing the position with a high degree of precision, such as agriculture, civil engineering and the development of autonomous vehicles.
He talks about all this today Jose Antonio Sanchez Sobrinoengineer in Geodesy and Cartography, head of the Geodetic Programs Service of the National Geographic Institute (IGN). I invite you to listen to it.
References:
National Geographic Institute
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