OSI Discovery Map Change - MountainViews.ie Article

This article is based on material that appeared in the MountainViews.ie monthly newsletter for May 2009 and is reprinted by agreement.

News Item: OS Map Changes

Big changes to 1:50,000 maps proposed.

* OSi Consultation on New Discovery Seriest.
* Existing "Irish Grid" to be replaced by all digit ITM references.
* 69 new sheets to replace the existing 89 sheets.
* New sheets to be double sided (that is a given "sheet" such as 5 would have half the map on each side.

The Ordnance Survey of Ireland (OSi) want to bring out a revised 1:50000 "Discovery" series of maps. This is described on the WAI website following a request to OSi for some background information. (Click Here) An equivalent series of maps would be published in Northern Ireland.
OSi are proposing consultation as outlined below.

What would you like in revised 1:50000 maps?

What would you like to see in new recreational maps? Weather resistant paper? Checking of forestry tracks? Summit names that don't obscure detail and maintain or return to a reasonable bilingual approach? Names for more features? - MountainViews has names for 1048 summits many of which are not named on OS maps. Detail checking of streams, tracks, houses and gardens etc? Well those would be some of the things I'd like to see.
Think out what you would like for inclusion because the OSi are asking for comment.

Using ITM

This is likely to prove the most controversial. OSi want to make a change to using the ITM projection and therefore ITM grid references because it involves less steps in production. As a benefit the large scale maps they produce for town planning etc would then fit exactly with the small scale maps used for recreation.
However this introduces difficulties for walkers. For example the usual Irish grid ref of Carrauntoohil is V803 844. Converting this GR to ITM in a shortened form this would be 4802 5844. The conversion from Irish Grid to ITM is NOT a simple arithmetical matter - the last digit of easting or northing representing 100 metres is likely to be different and for somewhere like Carrauntoohil that could be crucial.
The Irish Grid (or something very close to it) first appeared on maps in the 1940s. There has been extensive use of it in hillwalking books since the late 1970s. For example the late Tony Whilde's book "Irish Walk Guides - West" (1978) makes extensive use of grid references as do most more recent books. Newer books and magazines often describe interesting features out on the hills using grid references derived from GPS. All of these would now be hard to find on the newer maps and, while they can be converted, this is an exercise requiring a computer.
Many walkers have dozens of the existing maps and will have no intention of replacing them immediately so there will be a long messy period of at least 10 to 15 years while people have both. Another issue is that of competitive maps such as Harvey's, Healy's and the East-West map mentioned before. Are they going to change their projection to ITM?

Using GPS with ITM

Newer GPS units support ITM however older ones such as a Garmin GPS72 I bought in 2002 don't. So manual entry of GPS coordinates into an older GPS will have to continue to use Irish Grid. It will not be so easy to see your position on an ITM based map. Automated upload of data from say Gartrip, GPSU or OSi Trailmaster/ Geolives will not be affected whether or not your GPS has ITM because uploads have always been done using the worldwide standard WGS84 using geodectic lat/lon.

Websites such as MountainViews

MountainViews for example has thousands of grid references. Since these are held in electronic rather than paper form, they could be represented as ITM easily enough however the user interface will be more complicated to handle the likely long transition period if this change goes ahead. Where coords can be entered they will have to be enterable in either form and same for display.
Other websites using Irish grid may have considerable difficulty depending on whether they can readily be reprogrammed.

Consultation

OSi have arranged an online questionnaire about this which is at OSi Consultation The WAI who have taken a big interest in Modern Navigation (running courses on it) are arranging a consultation meeting with regards to this with OSi, to be held on 20th May. Places are strictly limited, preference being given to representatives of organisations who have an interest. If you are experienced in these issues and have a point of view it will be possible to contact the WAI shortly in relation to this.
You can comment on this article, below.

OSi have an online questionnaire Click Here

If you are interested in attending a consultative meeting with OSi Click Here

Further Information

Some more on the difference between systems for the summit of Carrauntoohil. According to the averaged readings from 4 MV members it is at V80357 84420. A full ITM grid ref would be 480333 584479. This illustrates the difference between the grids which in this case is -24m east and +59m north. However this difference varies at different places in Ireland because of the different underlying ellipsoids in use.
It also illustrates something else: in the simple conversion from 6 digit Irish grid to ITM, the resulting ITM grid in short form had a different easting (802) however taking in the more accurate summit position the eastings are the same (803). Whether this is true or not would depend on the 10s and units of metres figure for any given Irish grid ref.
The OSi have a tutorial at (Click here) As you will see if you read this the main drivers and main consultees for the proposed change have had nothing previously to do with recreational users.