ORDNANCE SURVEY MAPS The Basics Ordnance Survey Maps

ORDNANCE SURVEY MAPS

The Basics Ordnance Survey Maps in Ireland are produced by the OSi (Ordnance Survey of Ireland) The maps we use mostly are drawn to a scale of 1: 50, 000. This means that 1 cm measured on a map is equal to 50, 000 cm on the ground (ie: 500 m, which is 0. 5 km) Put another way, every 2 cm measured on one of these maps is equal to 1 km on the ground. Maps showing very large areas (eg: A map of Europe) have scales of approx 1: 500, 000. Maps of small areas (like part of a town) would have scales like 1: 8, 000 By knowing the scale the map is drawn to it allows you to measure distances.

Map Scale

Straight Line distance This involves calculating the distance between 2 points on a map in a straight line. This done by: Marking the 2 points on your map. Taking a strip of paper and laying it along the distance between the 2 points and marking them on the paper. Then placing the paper on the scale and reading off the measurement Give your answer in Kilometres

Reading your Result

Curved Line Distance This involves measuring the distance on a map between 2 points, along a curved feature like a Road. The process is the same as for a Straight Line distance but just involves more steps. Every time you come to a bend in the road you must carefully rotate the paper and mark it each time until you get to the end point. Then read to off on your scale, only paying attention to the first and last mark on your paper

STEP ONE STEP TWO STEP THREE

Map Symbols Features on a map are shown using symbols. These are found on the Legend Page on the back of a map. They are divided into different sections. All the symbols on a map are explained in the Legend. They include symbols for Garda Stations, Tourist Offices, Different types of roads, Historic Sites, etc

Giving a Grid Reference Every map of a part of Ireland has a place on the National Grid. This is represented by a Letter. This is called the SUB-ZONE LETTER

As well as the sub-zone letter each map contains 2 sets of numbers. They are called : EASTINGS and NORTHINGS. Eastings are the numbers that run along the top and bottom of the map. Northings are the numbers that run up either side of the map.

An easy way to remember which is to remember that Eastings are the numbers going Eastwards across the map And Northings are the numbers going North, up the side of the map.

EASTINGS SUBZONE LETTER N O R T H I N G S

A Grid Reference is given by combining these 3 things in the following order: LETTER EASTING NORTHING

A 4 -figure Grid Reference

A 6 -figure Grid Reference This is a more exact way of giving the location of a small item on a map like a Post Office, a Church, a School, etc It works like a 4 -figure reference except you now create imaginary decimal places. FOR EXAMPLE:

The 6 -figure Grid Reference for this Golf Course is… G 603 352