WEBVTT 00:00:00.500 --> 00:00:03.975 Welcome to GCSE A Q A Geography revision. 00:00:04.125 --> 00:00:07.173 Topic G 21: Geographical skills. 00:00:07.323 --> 00:00:12.176 Use your school’s selected case studies if they differ from these revision examples. 00:00:14.833 --> 00:00:21.958 Latitude measures angular distance north or south of the Equator; longitude measures east or west of the Greenwich meridian. 00:00:22.108 --> 00:00:25.029 Read the direction letters as well as the numbers. 00:00:27.700 --> 00:00:32.745 Describe distributions using location, concentration, gaps and exceptions. 00:00:32.895 --> 00:00:37.517 Use place names and map evidence rather than saying features are spread everywhere. 00:00:40.167 --> 00:00:50.682 The scale 1 to 25,000 means one map unit represents 25,000 of the same units on the ground: one centimetre represents 250 metres. 00:00:50.832 --> 00:00:55.503 At 1 to 50,000, one centimetre represents 500 metres. 00:00:58.167 --> 00:01:05.503 A larger-scale map, such as 1 to 25,000, shows a smaller area in more detail than 1 to 50,000. 00:01:05.653 --> 00:01:12.511 A scale bar remains useful when an image is resized; a printed ratio may no longer match physical ruler measurements. 00:01:15.167 --> 00:01:18.949 Measure straight-line distances with a ruler and the correct scale. 00:01:19.099 --> 00:01:24.376 For a curved route, use thread or short measured segments, then convert to ground distance. 00:01:27.033 --> 00:01:31.971 Area uses squared units: one square kilometre is one million square metres. 00:01:32.121 --> 00:01:36.315 A map square one kilometre on each side covers one square kilometre. 00:01:38.967 --> 00:01:42.077 Eastings increase to the east and northings to the north. 00:01:42.227 --> 00:01:46.661 Read along the corridor, then up the stairs: easting first, northing second. 00:01:49.333 --> 00:01:55.091 A four-figure grid reference identifies a square using the easting and northing of its south-west corner. 00:01:55.241 --> 00:01:57.833 It does not pinpoint the feature within the square. 00:02:00.500 --> 00:02:04.093 A six-figure reference divides each grid square into tenths. 00:02:04.243 --> 00:02:08.881 Give the three-digit easting then the three-digit northing without swapping their order. 00:02:11.533 --> 00:02:20.375 For an illustrative feature four tenths across square two three and seven tenths up square four five, the six-figure reference is two three four four five seven. 00:02:20.525 --> 00:02:24.665 This is a worked grid example, not the location of a named landmark. 00:02:24.815 --> 00:02:26.852 A six-figure grid reference. 00:02:27.002 --> 00:02:29.199 Read eastings before northings. 00:02:29.349 --> 00:02:33.991 This is an invented teaching grid, not an OS map of a real location. 00:02:38.667 --> 00:02:43.285 Compass directions include north, north-east, east and the other main points. 00:02:43.435 --> 00:02:52.021 Bearings are measured clockwise from north: east is zero nine zero degrees, south one eight zero degrees and west two seven zero degrees. 00:02:54.700 --> 00:02:58.725 Contours join points of equal elevation above the map's datum. 00:02:58.875 --> 00:03:04.123 Check their labels and contour interval; close contours usually indicate steeper slopes. 00:03:06.800 --> 00:03:09.787 Spot heights mark elevation at a particular point. 00:03:09.937 --> 00:03:15.898 A triangulation pillar is a surveyed feature and is not interchangeable with every spot-height symbol. 00:03:18.567 --> 00:03:23.847 Gradient is vertical change divided by horizontal distance in matching units. 00:03:23.997 --> 00:03:31.205 A 50 metres rise over 1,000 metres is 1 in 20; use horizontal distance, not the sloping path length. 00:03:31.355 --> 00:03:34.086 Calculate gradient using matching units. 00:03:34.236 --> 00:03:39.111 The horizontal and vertical dimensions are schematic, not drawn to the same scale. 00:03:39.261 --> 00:03:42.778 Do not use the length along the slope as horizontal distance. 00:03:47.433 --> 00:03:55.400 To draw a relief cross-section, mark contour crossings along a line and plot their heights against distance using a labelled vertical scale. 00:03:55.550 --> 00:03:58.407 Join them with a plausible smooth land profile. 00:04:01.067 --> 00:04:06.357 A transect records features along a line, such as land use from a town centre outward. 00:04:06.507 --> 00:04:10.775 It can show relationships but may not represent places away from that route. 00:04:13.433 --> 00:04:18.533 Use map symbols and the key to identify roads, buildings, woodland, paths and water. 00:04:18.683 --> 00:04:23.877 Infer tourism from a combination of evidence rather than one unexplained symbol. 00:04:26.533 --> 00:04:36.859 Compare coastal maps for headlands, bays, beaches and spits; river maps for meanders, floodplains and valley sides; glacial maps for steep corries, U-shaped valleys and lakes. 00:04:37.009 --> 00:04:41.153 Explain how contour and drainage evidence support identification. 00:04:43.833 --> 00:04:52.857 Ground photographs show a view from near the surface; oblique aerial images show a sloping view; vertical aerial or satellite images give an overhead view. 00:04:53.007 --> 00:04:56.151 Perspective affects apparent distances and sizes. 00:04:58.833 --> 00:05:04.091 Match photographs to maps using several landmarks, such as river bends, roads and hills. 00:05:04.241 --> 00:05:06.863 Check view direction and whether dates differ. 00:05:09.533 --> 00:05:14.791 A geographical sketch selects important features rather than copying every detail. 00:05:14.941 --> 00:05:19.495 Label observations and annotate explanations supported by evidence. 00:05:22.167 --> 00:05:28.939 G I S combines geographically located data in layers, such as population, flood zones and roads. 00:05:29.089 --> 00:05:34.645 Comparing layers can reveal patterns, but data accuracy and scale still limit conclusions. 00:05:37.300 --> 00:05:41.469 Bar charts compare categories and normally have spaces between bars. 00:05:41.619 --> 00:05:47.015 A line graph shows change across an ordered continuous variable, such as time or distance. 00:05:49.667 --> 00:05:53.839 Histograms display grouped numerical data with adjoining bars. 00:05:53.989 --> 00:06:01.422 For equal class intervals, frequency can be plotted consistently; do not treat unrelated categories as continuous classes. 00:06:04.100 --> 00:06:06.361 A pie chart shows parts of a whole. 00:06:06.511 --> 00:06:16.142 Calculate each sector as category value divided by total multiplied by 360 degrees; 25 percent makes a 90 degree sector. 00:06:18.800 --> 00:06:22.074 A divided bar also shows proportions of a total. 00:06:22.224 --> 00:06:28.965 Equal-length bars help compare percentages when group totals differ, but the absolute totals should still be stated. 00:06:31.633 --> 00:06:34.799 A pictogram uses repeated symbols for quantities. 00:06:34.949 --> 00:06:41.114 Include a key and interpret partial symbols correctly rather than enlarging symbols inconsistently. 00:06:43.767 --> 00:06:48.135 A scattergraph plots paired numerical values to investigate a relationship. 00:06:48.285 --> 00:06:51.471 Label both axes and plot each pair accurately. 00:06:54.133 --> 00:07:01.939 Positive correlation means values tend to increase together; negative correlation means one tends to decrease as the other increases. 00:07:02.089 --> 00:07:05.745 No clear correlation does not mean no conceivable connection. 00:07:08.400 --> 00:07:15.044 A line of best fit follows the overall pattern, rather than joining every point or forcing the line through the origin. 00:07:15.194 --> 00:07:18.531 Correlation does not by itself establish causation. 00:07:18.681 --> 00:07:21.454 Positive correlation and a best-fit line. 00:07:21.604 --> 00:07:26.968 Axes are schematic: these points illustrate a relationship and are not fieldwork results. 00:07:27.118 --> 00:07:31.619 A best-fit line follows the overall pattern rather than joining points. 00:07:36.300 --> 00:07:39.359 Interpolation estimates within the observed range. 00:07:39.509 --> 00:07:44.767 Extrapolation estimates beyond it and is less secure because the relationship may change. 00:07:47.433 --> 00:07:54.962 Population pyramids show age groups and sex categories, with population numbers or percentages on the horizontal axes. 00:07:55.112 --> 00:08:00.871 Read the units; a wide base suggests a large young share, not a precise future birth rate. 00:08:03.533 --> 00:08:09.421 Dispersion graphs show individual observations along a scale, making spread and clusters visible. 00:08:09.571 --> 00:08:13.881 Several groups with similar averages can still have very different spreads. 00:08:16.533 --> 00:08:19.964 Choropleth maps shade areas according to value classes. 00:08:20.114 --> 00:08:26.330 Rates or percentages are often more comparable than raw totals when areas have different populations. 00:08:29.000 --> 00:08:32.761 Choropleth boundaries can hide variation inside each area. 00:08:32.911 --> 00:08:38.255 Class thresholds and colour choices can change the apparent pattern, so read the key carefully. 00:08:40.933 --> 00:08:45.085 Isolines join equal values, such as temperature or rainfall. 00:08:45.235 --> 00:08:51.006 Close lines indicate rapid change across distance; contour lines are a height-based example. 00:08:53.667 --> 00:08:57.397 Dot maps represent quantities using dots of a stated value. 00:08:57.547 --> 00:09:03.489 A dot within a district may represent an allocation, not the exact location of each individual. 00:09:06.167 --> 00:09:09.260 Proportional symbols vary in size with quantity. 00:09:09.410 --> 00:09:14.657 If circle area is proportional to value, doubling the value does not double its radius. 00:09:17.333 --> 00:09:21.449 Desire lines join origins and destinations to show connections. 00:09:21.599 --> 00:09:27.838 Flow lines can use width and arrows to indicate quantity and direction; they may not trace the actual route. 00:09:30.500 --> 00:09:34.726 A ratio compares quantities, while a proportion is a part of a whole. 00:09:34.876 --> 00:09:40.378 Keep units consistent and state whether a figure is an absolute number, rate or percentage. 00:09:43.033 --> 00:09:46.252 Mean is total divided by number of observations. 00:09:46.402 --> 00:09:53.225 For illustrative readings 2, 3, 3, 6 and 11, the mean is 25 divided by 5 equals 5. 00:09:55.900 --> 00:10:00.923 Median is the middle value after ordering; with an even number, average the middle two. 00:10:01.073 --> 00:10:05.392 The illustrative set 2, 3, 3, 6, 11 has median 3. 00:10:08.067 --> 00:10:12.291 Mode is the most frequent value: the illustrative set's mode is 3. 00:10:12.441 --> 00:10:19.256 A modal class is the grouped interval with the highest frequency; it does not identify an exact individual value. 00:10:21.933 --> 00:10:24.365 Range is maximum minus minimum. 00:10:24.515 --> 00:10:31.350 For the illustrative set it is 11 minus 2 equals 9; the mean and range are both affected by extreme values. 00:10:34.000 --> 00:10:37.017 Quartiles divide ordered data into four parts. 00:10:37.167 --> 00:10:43.821 The inter-quartile range is upper quartile minus lower quartile and describes the middle half of the observations. 00:10:46.500 --> 00:10:51.363 Cumulative frequency is the running total at or below each class boundary. 00:10:51.513 --> 00:10:57.624 Use it to estimate the median at half the total frequency and quartiles at one-quarter and three-quarters. 00:11:00.300 --> 00:11:05.342 A percentile gives the value at or below which a stated percentage of observations falls. 00:11:05.492 --> 00:11:10.131 The 90th percentile is not the same as 90 percent of the maximum reading. 00:11:12.800 --> 00:11:20.041 Percentage change is the difference between the new and original values divided by original multiplied by 100. 00:11:20.191 --> 00:11:27.646 A rise from 40 to 50 is 25 percent; this is an illustrative calculation, not a case-study statistic. 00:11:30.300 --> 00:11:37.029 A rise from 40 percent to 50 percent is ten percentage points and a 25 percent relative increase. 00:11:37.179 --> 00:11:39.611 State which comparison you are making. 00:11:42.267 --> 00:11:46.131 Population density is population divided by area. 00:11:46.281 --> 00:11:53.427 For an illustrative 12,000 people over 30 square kilometres, density is 400 people per square kilometre. 00:11:56.100 --> 00:11:58.084 Use units and show working. 00:11:58.234 --> 00:12:04.889 Check whether an answer is reasonable and round only at the end when intermediate rounding would alter the result. 00:12:07.567 --> 00:12:13.955 Look for misleading axes, selective dates, inconsistent boundaries and averages that hide inequality. 00:12:14.105 --> 00:12:18.790 Compare absolute totals with rates before deciding one place performs better. 00:12:21.467 --> 00:12:25.515 Assess sample size, selection, measurement quality and data age. 00:12:25.665 --> 00:12:30.157 A precise-looking number can still be unreliable or unrepresentative. 00:12:32.833 --> 00:12:39.136 Quantitative evidence measures amounts; qualitative evidence explains characteristics or experiences. 00:12:39.286 --> 00:12:43.698 Using both can provide a fuller explanation when their limitations are considered. 00:12:46.367 --> 00:12:53.736 Describe states what the evidence shows; explain gives reasons; assess or evaluate weighs evidence to reach a judgement. 00:12:53.886 --> 00:12:57.829 Read the command word and focus on the specified place or issue. 00:13:00.500 --> 00:13:06.228 Extended answers need a connected argument, relevant evidence and a justified conclusion. 00:13:06.378 --> 00:13:11.156 Clear sentences and accurate geographical terms help communicate the reasoning. 00:13:13.833 --> 00:13:16.147 That completes Geographical skills. 00:13:16.297 --> 00:13:19.643 Revisit the notes and test yourself on the revision website.