1、 Op. ITU-R 91-2 1 OPINION ITU-R 91-2 World Atlas of Ground Conductivities (1993-1997-2007) The ITU Radiocommunication Assembly, considering a) the need for ground conductivity data when planning radiocommunication services, including those concerning navigation, in the VLF, LF and MF bands; b) that
2、the World Atlas of Ground Conductivities is published as Recommendation ITU-R P.832; c) the desirability for the World Atlas to contain ground conductivity data for all countries of the world; d) that there have been many changes of the borders between countries; e) that the effective conductivity f
3、or ground-wave propagation depends on the frequency being used; f) that the effective conductivity can only be measured by using suitable techniques which take account of the penetration depth of the radio waves into the ground; g) that for some types of geological ground structure and ground cover
4、there may be a seasonal and inter-annual change in effective conductivity; h) that the ITU-R can revise the data in the World Atlas of Ground Conductivities only on the basis of information from individual countries, is of the opinion 1 that administrations should check and, if necessary, revise the
5、 information given in the World Atlas, noting that in some cases seasonal changes may need to be included; 2 that new administrations should check that their needs are covered in the current World Atlas of Ground Conductivities and contribute to revisions of the data; 3 that for those countries for which no conductivity data are contained in the World Atlas, the administrations concerned should collect and provide data in accordance with the information given in Recommendation ITU-R P.832.
