📚 Year 9 Edexcel Geography: Formula and Theorem Quick Reference Handbook | Edexcel 九年级地理：公式定理速查手册
This quick reference handbook brings together the essential formulas, definitions, and calculation methods you will encounter in Year 9 Edexcel Geography. From map skills and population indicators to climate data and river processes, mastering these quantitative tools will help you analyse geographical patterns, interpret graphs, and answer exam questions with confidence.
这本速查手册汇总了 Edexcel 九年级地理课程中涉及的必备公式、定义和计算方法。从地图技能、人口指标到气候数据和河流过程，掌握这些定量工具将帮助你分析地理格局、解读图表，并在考试中游刃有余。
1. Map Scale | 地图比例尺
Map scale expresses the relationship between a distance on the map and the corresponding distance on the ground. It is usually given as a ratio (e.g. 1:50,000) or a linear scale. The formula to convert between map distance and real-world distance is straightforward.
地图比例尺表示图上距离与对应实地距离之间的关系，通常以比率（如 1:50,000）或直线比例尺给出。将地图距离换算为实际距离的公式很简单。
Scale = Map Distance ÷ Ground Distance
比例尺 = 图上距离 ÷ 实际距离
If the scale is 1:25,000, then 1 cm on the map represents 25,000 cm (or 0.25 km) on the ground. Always ensure that both distances use the same unit before performing any calculation.
如果比例尺为 1:25,000，则地图上的 1 厘米代表实地 25,000 厘米（即 0.25 千米）。计算前务必确保两个距离使用相同的单位。
- Example: map distance of 4 cm at a scale of 1:50,000 equals 4 × 50,000 = 200,000 cm, which is 2 km.
- 示例：在比例 1:50,000 的地图上量得 4 厘米，实际距离为 4 × 50,000 = 200,000 厘米，即 2 千米。
2. Measuring Distance on a Map | 地图上的距离测量
Straight-line distance can be measured with a ruler and converted using the scale. Curved distances, such as along a river or a winding road, are measured using a piece of string, a strip of paper, or an opisometer, and then compared against the linear scale.
直线距离可用直尺量测后通过比例尺换算。弯曲的距离，如河流或蜿蜒道路的长度，可用细线、纸条或曲线计（量图仪）量出，再与直线比例尺比对。
Real Distance = Map Distance (cm) × Scale Factor (cm)
实际距离 = 图上距离（厘米）× 比例尺因子（厘米）
00,000 cm = 1 km). Practising with different line types builds skill in route measurement.
请记住将最终结果转换为千米：除以 100,000（因为 100,000 厘米 = 1 千米）。练习不同类型的线条有助于提高路线测量技能。
3. Calculating Area from Maps | 地图面积计算
When you need to find the area of a feature (e.g. a forest, a lake, or a farmland), you can use grid squares. On many maps, each grid square is 1 km². Count the full squares and estimate partial squares to arrive at the total area.
当需要计算某一要素的面积（如森林、湖泊或农田）时，可利用网格方格。许多地图上每个方格代表 1 平方千米。数出完整的方格并估算部分方格，即可得出总面积。
ea = (Number of Full Squares + Estimated Fraction of Partial Squares) × Area of One Square
面积 = （完整方格数 + 部分方格的估算份额）× 单个方格面积
For irregular shapes, the dot grid method or transect strips can also be used. In an exam, you are usually provided with the scale of grid squares; read the question carefully before counting.
对于不规则形状，也可使用点格法或样带条法。考试中通常会给出方格的比例，数格前请仔细审题。
4. Gradient | 坡度
Gradient measures the steepness of a slope. It is the ratio of vertical interval (the difference in height between two points) to the horizontal distance, often simplified to a ratio such as 1:10.
坡度表示斜坡的陡峭程度，它是两点间的高差（垂直间距）与水平距离之比，通常简化为 1:10 这样的比率。
Gradient = Vertical Interval ÷ Horizontal Distance
坡度 = 垂直间距 ÷ 水平距离
1,000 = 1/10, expressed as 1:10. Both measurements must be in the same unit (e.g. metres).
例如，高差为 100 米，水平距离为 1,000 米，则坡度为 100/1,000 = 1/10，表示为 1:10。两项测量必须使用相同单位（如米）。
5. Birth Rate and Death Rate | 出生率与死亡率
Birth rate is the number of live births per 1,000 people per year. Death rate (or mortality rate) is the number of deaths per 1,000 people per year. These crude rates are essential for studying population change.
出生率指每年每千人中的活产婴儿数。死亡率（或粗死亡率）指每年每千人中的死亡人数。这些粗率是研究人口变化的基础。
Birth Rate = (Total Live Births ÷ Total Population) × 1,000
出生率 = （活产总数 ÷ 总人口）× 1,000
Death Rate = (Total Deaths ÷ Total Population) × 1,000
死亡率 = （死亡总数 ÷ 总人口）× 1,000
Rates are expressed 'per 1,000' to make comparisons between countries of different population sizes meaningful. You will often see them on demographic transition graphs.
比率以“每千人”表示，这样在人口规模不同的国家之间比较才更有意义。你会在人口转型图中经常看到它们。
6. Natural Increase Rate | 自然增长率
Natural increase (or natural change) is the difference between the birth rate and the death rate. It ignores migration and shows how a population is changing through births and deaths alone.
自然增长（或自然变动）指出生率与死亡率之差，它不考虑迁移，仅显示因出生和死亡引起的人口变化。
Natural Increase Rate = Birth Rate − Death Rate
自然增长率 = 出生率 − 死亡率
The result is usually given as a percentage or as a per-1,000 figure. A positive value means the population is growing; a negative value (natural decrease) means it is declining, ignoring migration.
结果通常以百分比或千分比表示。正值表示人口在增长；负值（自然减少）表示人口在下降，同样不考虑迁移。
7. Population Density | 人口密度
Population density describes how crowded an area is. It is the average number of people living per square kilometre (or sometimes per square mile).
人口密度描述一个地区的拥挤程度，它指平均每平方千米（有时每平方英里）居住的人口数。
Population Density = Total Population ÷ Total Land Area (km²)
人口密度 = 总人口 ÷ 总土地面积（平方千米）
For example, if a country has 10 million people and an area of 500,000 km², its population density is 20 people per km². High-density areas can be cities, while low-density areas may be deserts or mountainous regions.
例如，某国人口 1,000 万，面积 50 万平方千米，则其人口密度为每平方千米 20 人。高密度地区可能是城市，低密度地区则可能是沙漠或山区。
8. Urbanisation Rate | 城市化率
The urbanisation rate measures the percentage of a country’s population living in urban areas. It can also refer to the speed of urban growth over time.
城市化率衡量一个国家生活在城镇地区的人口百分比，也可指城市增长的速度。
Urbanisation Level (%) = (Urban Population ÷ Total Population) × 100
城市化水平（%）= （城市人口 ÷ 总人口）× 100
In Edexcel Geography, you may be asked to compare urbanisation rates between HICs, MICs and LICs, or to interpret population pyramids and discuss the growth of megacities. The rate of urbanisation is the annual percentage increase in the urban share.
在 Edexcel 地理中，你可能需要比较高收入国家、中等收入国家和低收入国家之间的城市化率，或解读人口金字塔，讨论超大城市的增长。城市化速度指城市人口占比的年增长率。
9. Temperature Range and Mean Annual Precipitation | 气温范围与年均降水量
When reading climate graphs, the temperature range is the difference between the highest and lowest average monthly temperatures. Mean annual precipitation is the total rainfall (or melted snow) over a year, usually given in millimetres.
在阅读气候图表时，气温范围指月平均气温最高值与最低值之差。年均降水量是一年中的总降雨量（或融化后的雪量），通常以毫米计。
Temperature Range = Maximum Monthly Temp. − Minimum Monthly Temp. (°C)
气温范围 = 月平均最高气温 − 月平均最低气温（°C）
Mean Annual Precipitation = Sum of All Monthly Precipitation (mm)
年均降水量 = 各月降水量之和（毫米）
Although mean annual precipitation is not a 'formula' in the strict sense, it is a critical calculation for describing climate. You may also need to identify seasonal distribution: do most rains fall in summer or winter?
虽然年均降水量并不算严格的“公式”，但它是描述气候的关键计算。你还可能需要判断降水的季节分布：大部分雨水是降在夏季还是冬季？
10. GDP per Capita | 人均国内生产总值
Gross Domestic Product (GDP) per capita is a common indicator of a country’s standard of living. It is calculated by dividing the total value of goods and services produced in a year by the mid-year population.
人均国内生产总值是衡量一国生活水平的常用指标，其计算方法是将一年内生产的商品和服务的总价值除以年中人口数。
GDP per Capita = Total GDP ÷ Total Population
人均 GDP = 国内生产总值 ÷ 总人口
In Edexcel Year 9, you will use GDP per capita (often in US dollars) to classify countries into high-income, middle-income and low-income groups. Remember that it is an average and does not show income inequality within a country.
在 Edexcel 九年级中，你将用人均 GDP（通常以美元计）把国家划分为高收入、中等收入和低收入组。请记住这是一个平均值，并不反映国内收入不平等的状况。
11. River Discharge | 河流流量
River discharge is the volume of water flowing through a river channel at a given point and time, usually measured in cubic metres per second (cumecs). It is essential for understanding flood risk and river regimes.
河流流量指某一时刻流经河道某断面的水量，通常以立方米每秒（cumec）计量。它对理解洪水风险和河流情势至关重要。
Discharge (Q) = Cross-sectional Area (A) × Velocity (V)
流量 (Q) = 横截面积 (A) × 流速 (V)
To find the cross-sectional area, multiply channel width by mean depth. Velocity can be measured using a flow meter or a float. Even simple fieldwork can apply this formula; just be consistent with units (m² for area, m/s for velocity).
计算横截面积时，用河道宽度乘以平均水深。流速可用流速仪或浮标测量。即使简单的实地考察也可应用此公式，只需单位一致（面积用平方米，流速用米/秒）。
12. Coastal Erosion Rate | 海岸侵蚀速率
Coastal erosion is often measured as the average annual loss of land, typically given in metres per year. The formula is straightforward, but accurate data relies on repeat surveys or historical map comparisons.
海岸侵蚀常以年均土地损失量来表示，通常以米/年为单位。公式很简单，但准确的数据依赖于重复测量或历史地图比对。
Erosion Rate = Distance of Land Lost ÷ Time Period (years)
侵蚀速率 = 损失的土地距离 ÷ 时间段（年）
For example, if a cliff retreats 30 metres over 20 years, the average erosion rate is 1.5 m/year. This indicator helps geographers evaluate the effectiveness of sea defences and predict future coastline changes.
例如，一处悬崖在 20 年间后退了 30 米，则平均侵蚀速率为 1.5 米/年。这一指标有助于地理学家评估海防工程的有效性并预测未来岸线变化。
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