Swepos changes antenna models

On 11 November 2019, Swepos will switch to using the new antenna models that have been developed and are now used by IGS (International GNSS Service), igs14.atx.

An antenna model describes the relationship between the electrical measuring points that the GNSS measurements primarily refer to and a physical point on the antenna (ARP, Antenna Reference Point). The coordinates of a station are closely related to the antenna model used, as it is the antenna model that relates the measurements to a physical point which can then be linked to the geodetic marking to which the station coordinates refer. Changing the antenna model therefore gives changed coordinates.

To compensate for the difference between the old (igs08.atx) and new antenna models at the Swepos stations, the coordinates of the stations are updated.

Read more about antenna models and why they are updated (pdf, 0.1 MB, new window).

Network RTK

Regarding Network RTK, it should be noted that the new antenna models have already been introduced with a previous upgrade of the software that delivers the RTK corrections.

The change of antenna models and station coordinates may make a small difference in the result when using Network RTK, mainly depending on the type of antenna and antenna model used in the field measurement and the type of antenna used at the nearest Swepos station.

We are not able to perform complete tests of Network -RTK before the introduction of the updated coordinates, partly we do not have access to all rover equipment / antenna types on the market, partly we have no control over which antenna models are used in different rover receivers; some have probably already introduced igs14.atx and others may still uses relative antenna models. 

Swepos Calculation Service has been tested with the new antenna models and updated coordinates at the Swepos stations and there the differences are small. The calculation service uses the same calculation model (ionospheric-free linear combination and estimation of tropospheric parameters) as the calculation that is the basis for updating the coordinates of the Swepos stations. Then other Swepos services, i.a. network RTK, partly using other calculation models (mainly L1 in the final solution) one can expect to get a slightly larger difference when updating Network RTK.

Tests have been performed by the project-adapted calculation services (pdf, 0.2 MB, new window) which has been developed in collaboration with, among others, the Swedish Transport Administration, where L1 is used in the final solution. The introduction of igs14.atx and adapted station coordinates also means some major differences here. All horizontal differences are within 2 mm and the maximum deviation is 6 mm in height. in Network RTK would be significantly larger.

The general recommendation is that users of Network RTK should primarily use the antenna model found in igs14.atx for the rover receiver's antenna - according to the principle to use the most modern antenna models as they hopefully correspond better with reality than older antenna models. However, horizontal offset values or azimuth-dependent variations should not be used if the antenna is not oriented to the north when measuring.

A possible change of antenna model does not need to take place in direct connection with the updates of Swepo's Network RTK. Contact your GNSS dealer to find out their antenna model recommendations, get information about the antenna model used in your rover equipment and, if necessary, get help updating your antenna model.

Calculation Service

The change to the new antenna models can give a small difference in the result when using the calculation service, mainly depending on the type of antenna and antenna model used in the measurement in the field.

A larger number of calculation jobs have recalculated with the new antenna models and updated station coordinates in Swepos Calculation Service (pdf, 0.2 MB, new window). In the test material, the maximum deviation was 7 mm in height and 4 mm in plane. height and the maximum deviations 2 mm in plane and 4 mm in height, which shows that the updated coordinates of the Swepos stations compensate for the antenna model differences.

Contents of this page may be automatically translated, we take no responsibility for the accuracy of the translation. Feel free to contact our customer support centre if you have any questions.

Read more about our website