Data Sources (in no particular order)

All programs are created by me, although I have borrowed some code from few places (mentioned below),
but the data is all from other sources, this site would be nothing without data! If you use any of these sources on your own site then please aknowledge the original site, some are still in copywrite and permission should be sought first.

Where images have been reproduced the source is mentioned on the page in question, Ordnance Survey sourced outline maps are “Reproduced by kind permission of Ordnance Survey © Crown Copyright NC/2004/35281”

UK Trigpoints

This dataset is taken from Trigonomy Yahoo Group [ Release no. 3.06 (29 February 2004)], many thanks to the many contributors that have put together the list.

Of course ultimate credit goes to the Ordnance Survey who installed all the various types of markers, and at different points have released various lists that the above datasets are based upon.

Levelling Benchmarks

Recently data from the Second Geodetic Levelling of Great Britain has come to the attention of members of Trigonomy, this is in the form of a report made by Colonel Sir Charles Close in 1921. Currenty this data is being transcribed to digital format, mainly by members of Trigonomy.

We have also got hold of a abstract of the First Geodetic Levelling. And lots of files have been found at The National Archives including slides.

Some data about non pillar flush brackets are taken from the MSN OSBM Group, again thanks to the contributors.

Irish Trigpoints - Northern Ireland and Republic of Ireland

Compiled by members of Trigonomy by visually scanning 50k maps.

The OSI have also kindly supplied a list of Primany stations.

Location Search

See Information about the datasets, for links to the websites where the data is taken from. The sets are either obtained by (in order of preference) negotation with the maintainer, use of the bulk download option on the site or webscraped. (a few use a live download, because the dataset is large and/or regullay updated, eg Geocaches)

The results for the General Web Search (still in Alpha) are obtained by running general searches for 'Grid Ref' and then parsing the webpages for anything that resembles a grid reference. As time progresses this alogorithm will probably be refined somewhat. It is actully along similar lines to SearchArea Demo, but using GR rather than Postcodes and placenames. I have avoided looking for postcodes to help cut down on the number of general sites turned up - I am looking for more specialist results. Similally could also parse links to streetmap/mutlimap to get a location, but the number of results would increase and lower the quality.

Interactive Map

Coastline - NGDC-WDC MGG, Boulder-Coastline Extractor via Jonathan Russell

Second Geodetic Levelling Benchmarks - the abstract by the OS and many contributers to the transcription project.

non pillar flush brackets - are taken from the MSN OSBM Group, again thanks to the contributors.

Landranger Outlines - Lez Watson via Jonathan Russell

Explorer Outlines - Personally compiled by Ian Richardson

Primary Trigs and Secondary Blocks - Compiled by Graeme Paterson from the History of the Retriangulation of Great Britain

Secondary Trigs - from the OS via

Motorways, A Roads, Urban Areas, Coastline - Compiled from the Digital Chart of the World by

Rivers, Lakes and Railways - Compiled from the Digital Chart of the World

Populated Places - For the moment from T:UK, but hope to extract from Digital Chart of the World

TrigpointingUK Section

The data is taken direct from, so the data is based on the sources used in compiling the site.

Small Outline Map of UK - Reproduced from Ordnance Survey map data by permission of the Ordnance Survey © Crown copyright 2001.

Bayesian Weighted Rank calculation - from Freshmeat

Co-ordinate Converter

OSGB/OSI grid to WGS84 - approximate alogrithm from - NOT USED ANY MORE!

GridRef/Easting&Northing <=> Lat/Long - Geography::NationalGrid CPAN Module - after fixing a few bugs!

OSGB36 <=> WGS-84 (both Lat/Long) - Helmert Transformation, from OS Spreadsheet, with help from Teasel from (includes Lat/Long => XYZ)

Easting/Northing <=> Grid Reference <=> Map Tile Reference - (GB & Ireland) - Self Developed

UTM <=> Lat/Long - Geo::Coordinates::UTM CPAN Module

IARU Locator <=> Lat/Long - Self Developed from examples online

Approx <=> Lat/Long - Geo::Approx CPAN Module

NAC <=> Lat/Long - Used under Licence from NAC Geographic Products Inc

Also thanks to wildlifewriter who has helped immensely with debuging the Eastings/Northings <=> Lat/Long calculations!

UK Postcode Sector to GridRef - unknown source, but as I remember it was from a American developed product which said they found the data freely available (this was in 2002 - so could be well out of date) - have since seen this data in many places!

Postcode areas -

UK Std Telephone Codes Areas -

UK Std Telephone Codes to GridRef - PocketGPS

Pre 1974 Counties - complied by Ian Richardson

Post 1974 Counties - algorithm from

Landranger Outlines - Lez Watson via Jonathan Russell

Explorer Outlines - Personally compiled by Ian Richardson

Irish Discover/Discovery Outlines - Tom from (NEW!)

UK PlaceName Gazetteer

Toponymic information is based on the Geographic Names Data Base, containing official standard names approved by the United States Board on Geographic Names and maintained by the National Geospatial-Intelligence Agency. More information is available at the Products and Services link at The National Geospatial-Intelligence Agency name, initials, and seal are protected by 10 United States Code Section §445.

Background Picture

myself - its Moel Oernant

External Sites

Also a big thanks to the siteswith geospatial information that allow linking to them, these are used quite a bit in the Co-ordinate Converter, they provide far more information than I hope to be able to provide. Also the source sites for the Location Search datasets deserve another mention.

( Home | Location Search | Levelling | Coordinate Converter | Map Sites | Sources | Links )

This page created by Barry Hunter (c)2005 part of TrigTools