Article: 486 of sci.geo.satellite-nav Newsgroups: sci.geo.satellite-nav From: "Dave Saville" Message-ID: Reply-To: "Dave Saville" X-Newsreader: PMINews 2.00.1205 For OS/2 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Subject: accuracy check in UK Lines: 36 Date: Thu, 25 Oct 2001 13:29:35 +0100 (BST) NNTP-Posting-Host: 195.44.211.212 X-Trace: news2-hme0 1004012982 195.44.211.212 (Thu, 25 Oct 2001 13:29:42 BST) NNTP-Posting-Date: Thu, 25 Oct 2001 13:29:42 BST Path: news.meer.net!sea-read.news.verio.net!dfw-artgen.news.verio.net!dfw-peer.news.verio.net!news.verio.net!crtntx1-snh1.gtei.net!washdc3-snh1.gtei.net!news.gtei.net!feeder.qis.net!btnet-peer!btnet!newspeer.clara.net!news.clara.net!peernews!peer.cwci.net!news2-hme0.POSTED!not-for-mail Xref: archive.mv.meer.net sci.geo.satellite-nav:486 Out of interest and because I have not seen this mentioned before........ ( but I guess you all knew it anyway :-) ) The Ordnance Survey has thousands of trig points all over the UK. What they have done is designate some as GPS check points. On their website http://www.gps.gov.uk/info.asp is a searchable database. This gives data on the point, what type of marker it is, how to reach it etc. The coordinate are in ETRS89 cartesian & geodetic and National grid. I asked the OS about ETRS89 as I had not seen it mentioned before: "The national coordinate systems are used in a great variety of applications by many different user groups. ETRS89 is a precise version of the GPS coordinate system WGS84, and is the standard coordinate system for precise GPS positioning throughout Europe. " I checked my GPS12 set for WGS84 against three markers with a 3d lock, heights are averages over several readings. Lat Long Alt (Ellipsoid height) EPE OS N 51 19 3.9792 E 0 12 42.4191 249m GPS N 51 19 4.4 E 0 12 42.5 230m 13feet OS N 51 27 35.1008 W 0 1 25.9836 96m GPS N 51 27 35.1 W 0 1 25.8 72m 14feet OS N 51 18 26.2491 W 0 0 31.5654 267m GPS N 51 18 26.5 W 0 0 31.3 239m 1feet Regards Dave Saville NB switch saville for nospam in address