Continuing our look at Primary and Secondary data presentation.
Scatter Graph. <ul><li>Scatter plots are used to show a relationship between two data sets. The dependent data should be placed on the horizontal (x) axis. The points should not be joined up but a line of best fit showing the general trend is useful where there is an obvious correlation. </li></ul>
Line Graph <ul><li>Line graphs show changes over time. All the points are joined up and the axes should normally begin at zero. Rates of change are shown well, although careful thought to the scale should be given. Unsuitable if there are only a few data points. </li></ul>
Homework. <ul><li>Answer the following questions that could be typical of the type of questions you would get in an exam on graphs. </li></ul><ul><li>Give 4 features of a well presented and appropriately used bar graph. </li></ul><ul><li>Give an example of an occasion when you would use a histogram rather than a bar graph, and say how you would construct it. </li></ul><ul><li>State 2 advantages and 2 disadvantages of using bar graphs in a geographical investigation. </li></ul>
Secondary Data. <ul><li>The most common form of secondary data presentation is the use of maps. </li></ul><ul><li>Purpose of maps: </li></ul><ul><li>Maps are important to geographers. </li></ul><ul><li>They represent features of the land and are useful to show spatial patterns. </li></ul><ul><li>Every geographical investigation should make use of published maps to locate the study area, and many are likely to involve base maps onto which results can be drawn. </li></ul><ul><li>Base maps can vary from a homemade sketch maps to copies of Ordnance Survey maps and outlines of the UK. </li></ul>
What are the uses of maps? <ul><li>Locates the study area and helps to guide sampling decisions. </li></ul><ul><li>Show changes over time when maps of different survey dates are compared. </li></ul><ul><li>Maps of urban areas show clear functional zones, building density, street patterns, transport links etc. </li></ul><ul><li>Contours indicate the shape of the land: height and gradient of slopes. </li></ul><ul><li>Patterns of urban growth and pressure on the countryside can be identified by studying the location of urban zones, golf courses, motorways etc. </li></ul><ul><li>Maps of rural areas show the intensity of agricultural use and highlight natural/undeveloped regions. </li></ul>
Task <ul><li>How many maps can you think of. </li></ul><ul><li>2 minutes. </li></ul>
What are our main types of Maps. <ul><li>Ordnance Survey </li></ul><ul><li>1:125,000 (road atlas scale: shows wide area/region; useful for showing sphere of influence) </li></ul><ul><li>1:50,000 Landranger (2cms = 1km scale: useful for identifying study area and broad land uses such as rural/urban) </li></ul><ul><li>1:25,000 Explorer (4cms = 1km scale: useful to aid sampling decisions and can be adapted to produce a suitable base map) </li></ul><ul><li>1:10,000 Landplan (10cms = 1km scale: shows patterns of land use in both urban and rural areas; street map detail) </li></ul><ul><li>1:2,500 Superplan (40cms = 1km scale: very detailed showing individual buildings, pavements and shops). </li></ul>
Goad Maps. <ul><li>GOAD PLANS (published by Charles Goad not the Ordnance Survey) These are modern large scale plans for town centres and although the Surrey History Centre holds some plans for some towns you may find that if there is a large library in the town you're interested in they may have a copy of the map you want there. Goad plans are produced every year and this makes them particularly useful for tracing the recent development of town centres. </li></ul>
Finally. <ul><li>Geology and Soil maps </li></ul><ul><li>Sketch maps, Dot maps, Choropleth maps, </li></ul><ul><li>Topological maps (London Underground) and Isoline maps. </li></ul>
The Limitations of Maps. <ul><li>Selecting the correct scale of map is important and will depend on the purpose it's trying to serve. </li></ul><ul><li>The more detailed the map the less area it covers and so a spatial pattern may not become obvious. </li></ul><ul><li>It should also be remembered that maps are "snapshots" in time and are likely to be out of date as soon as they are published! </li></ul><ul><li>Specialist maps are expensive but fortunately Ordnance Survey maps at up to 1:25,000 scale can be downloaded from the web. </li></ul>
What do these maps look like? <ul><li>I am now going to show images of all these maps highlighting the limitations of some types. </li></ul>
Sketch Maps <ul><li>Sketch maps </li></ul><ul><li>valuable to students completing a geographical investigation. They simplify what is shown on published maps (such as Ordnance Survey) by only showing the features that are of interest. </li></ul><ul><li>As such unnecessary detail is ignored and the map is easier to interpret. </li></ul>
Dot Maps. <ul><li>Dot maps </li></ul><ul><li>use small dots of a fixed size to represent a variable, such as numbers of people, shops, etc. located on a base map. </li></ul><ul><li>The value of each dot should be high enough to avoid extremes and low enough to avoid too many areas having no data plotted giving the false impression of emptiness. </li></ul><ul><li>Different coloured dots could be used to represent different data for comparison. </li></ul><ul><li>These maps are helpful to show distributions but they do have limitations: (a) it is very difficult to count a large number of dots so accurate reading of the map is not possible; (b) this mapping technique relies on the dots being plotted accurately on a map representing a specific location rather than a broad region - detailed knowledge of the data is therefore necessary. </li></ul>
Choropleth Maps <ul><li>Also known as density shading maps. </li></ul><ul><li>Areas are shaded according to a key representing a range of values. </li></ul><ul><li>It is an easy presentation technique which gives a good visual impression of change over space . </li></ul><ul><li>It relies on a suitable key and is limited by the following: </li></ul><ul><li>(a) it gives a false impression of abrupt change at the boundaries; </li></ul><ul><li>(b) variations within each area are hidden, particularly if a wide data range is used; </li></ul><ul><li>(c) reading exact data figures from the map isn't possible. </li></ul><ul><li>All areas should be shaded unless there is "no data" for an area. </li></ul><ul><li>There are 3 ways the data can be grouped into classes: (i) divide the range of values into equal-size classes; </li></ul><ul><li>(ii) rank the values in order and then divide the list into the number of groups you want; </li></ul><ul><li>(iii) inspect the data values carefully and divide them up to reflect the distribution of the data (good with extreme values). </li></ul>
Lets pick out these limitations. <ul><li>Use the atlases to find a Choropleth Map and a Dot map showing the population of the world. </li></ul><ul><li>Use Egypt as an example to show the differences. </li></ul>
Topological Maps <ul><li>Topological maps </li></ul><ul><li>use area or distance to represent values. Actual distance and direction are disregarded but the relative position of places is retained. There are two types: </li></ul><ul><li>(1) Maps of areas (e.g. countries) in which the area has been distorted to be proportional to some value (such as population, GNP etc.) (2) Maps of route networks , e.g. the London Underground Map. These maps retain the relative position of each station. They are much easier to read and understand than conventional maps. </li></ul>
Isoline Maps. <ul><li>Isolines- lines on a map that join points of equal value, e.g. contours on a relief map, isotherms of temperature, isobars of pressure, etc. </li></ul><ul><li>The interval between the Isolines should be consistent and the numerical values should be added to each line. </li></ul><ul><li>They only work where there is plenty of data spread all over the study area and the changes across space are fairly gradual. They avoid the problems that boundary lines create on choropleth maps. </li></ul>
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