This map shows the locations of about 900 passive GPS stations in Great
Britain which will be available from 2000. The red dots are passive
stations which are co-located with OS fundamental bench marks, and
the yellow dots are passive stations which are co-located with OS
triangulation monuments. The black dots are purpose-made GPS monuments.
Some passive stations are re used triangulation pillars or fundamental
benchmarks; others are purpose-built GPS marks such as buried concrete
blocks or Berntsen markers. All these types of passive station have
GPS coordinates of the same high quality, and are equally good for
the purpose of controlling GPS surveys in the ETRS89 coordinate
system. In addition to those shown on this map, new passive stations
on several Scottish islands will be installed during 2000.
