1/28/16. EGM101 Skills Toolbox. Map types. Political Physical Topographic Climate Resource Road. Thematic maps (use one of the above as backdrop)

Transcription

1 EGM101 Skills Toolbox Map types Political Physical Topographic Climate Resource Road Thematic maps (use one of the above as backdrop) Map Types Deriving information from maps Hydrographic Geological Soils Vegetation Etc. Ordnance Survey Maps The Irish Grid is defined as a system of squares whose North-South lines (Eastings) are parallel to the central meridian and whose East-West lines (Northings) are at right angles to it. The grid appears on the published map as an overall pattern of squares, the grid interval being appropriate to the scale of the map that carries the squares. The layout of the 10 kilometre square relating to Northern Ireland is thus: To simplify, referencing Ireland is assumed to be covered by a number of squares, each with 100 kilometre sides and designated by a unique letter. The use of the letter reduces the number of digits required for a grid reference and also serves as a rough indicator of locality to those familiar with the system. 1

2 Ordnance Survey Maps Grid References Grid references are used to indicate the location of a given point or feature They consist of a grid letter in combination with an even number of digits made up of Northings and Eastings. The number of digits in a grid reference depends on the map being used, and the distance Eastward (Easting) is always written or quoted before the distance Northward (Northing). e.g. P (a) 1:1,000,000 scale 1cm = 10 km. Only show cities and major towns together with the motorway and primary route network. County boundaries are shown and are sometimes colour coded to make their shape and location clearly distinguishable. (c) 1:250,000 scale (b) 1:625,000 scale 1cm = 6.25 km Only major towns and cities are detailed together with major roads and rivers. Used for administrative purposes by businesses and government departments wanting to view very large areas of the country. They are also useful for planning journeys over long distances. 1cm = 2.5 km. Map detail is confined to place names and the road network with extent of urban areas shown by a grey background. Large forests and parks are also highlighted by colour. Major river networks are also shown. Map symbols are used extensively to highlight places of interest, again because of the lack of space. These maps are used for planning routes or navigation. (d) 1:50,000 scale 1cm = 500 m. Individual buildings are grouped together as blocks. In rural areas, field boundaries do not appear. This scale of map is for generalpurpose use, for example, business planning, motoring, walking and cycling. 1:25,000 scale 1cm = 250 m. At 1:25,000 scale, major buildings such as the City Hall are clearly visible; other features such as field boundaries also appear in rural areas. Maps at 1:25,000 scale are used by walkers and other outdoor enthusiasts but they also contain enough detail for local area planning purposes. 2

3 1:10,000 scale 1cm = 100m Alternatively, 6¼ inches on the map is equal to 1 mile on the ground. Roads, road names and major buildings are clearly marked together with rivers, streams and other land features. Useful for town planners, builders and farmers who require a high level of detail for a relatively large area. Field workers (geologists, biologists, geomorphologists etc.) generally rely on these maps as basemaps for field surveys. (g) 1:1250 scale 1cm = 12.5 m. At this scale, roads, buildings, fences and landscape features are shown in detail. The shapes of individual buildings are accurately represented as well as being named or numbered. This scale of mapping covers urban areas only. Used by central and local government, utilities (gas, electricity, water and telecommunications companies). Contour (topographic) Maps Height (m) Contour lines are a method of depicting the 3-dimensional character of the terrain on a dimensional map Contour lines drawn on the map represent equal points of height above sea level

4 A variety of surface features can be identified from contour lines. Steep slopes - contours are closely spaced. Gentle slopes - contours are less closely spaced. Valleys - contours form a V-shape pointing up the hill - these V's are always an indication of a drainage path which could also be a stream or river. Ridges - contours form a V-shape pointing down the hill. Summits - contours forming circles. Depressions - are indicated by circular contour with lines radiating to the centre. Admiralty Charts / Hydrographic charts Admiralty Charts are the marine equivalent of Ordnance Survey maps. In addition to detailing the water depth and the charted position of high- and low-water at the shoreline, Admiralty Charts also provide mariners with information on substrate type (the type of sediment comprising the seafloor), the strength and orientation of tidal currents, underwater hazards, magnetic deviation and information to aid accurate navigation at sea. Information on Admiralty Charts Geological Maps Substrate type Currents Water depth Wrecks Navigation Markers Placenames HWM & LWM The geology of an area has a profound effect on many aspects of the environment, from the likelihood of landslides, to the availability of groundwater in wells, from the amount of shaking suffered in an earthquake, to the presence of mineral resources, from the way the landscape is shaped to the kinds of plants that grow best there. Understanding the structure, morphology and composition of the Earth is usually fundamental to the investigation of the surface elements of the Earth - ranging from biology to hydrology to archaeology. Co-ordinates 4

5 A geological map is usually printed on top of a regular map (usually an ordnance survey map) to help you locate yourself. The base map is printed with light colours, so it doesn t interfere with seeing the geologic features on the map. The geology is represented by colours, lines, and special symbols unique to geological maps. Understanding these features will allow you to understand much of the geology shown in almost any standard geological map. 5

6