📚 Year 7 OCR Geography: Formula & Theorem Quick Reference | Year 7 OCR 地理：公式定理速查手册
This quick reference handbook collects all the essential formulas, calculations, and key geographical ‘rules’ that a Year 7 student following the OCR Geography course will need. From mapwork skills to population data, keep this page bookmarked for easy revision.
这本速查手册汇集了跟随 OCR 地理课程学习的七年级学生所需的所有基本公式、计算以及关键的地理“规律”。从读图技能到人口数据，请将此页面加入书签以便于复习。
1. Map Scale (Ratio and Statement) | 地图比例尺（比率与文字）
The map scale tells you the relationship between a distance on the map and the real distance on the ground. It can be written as a ratio (e.g., 1:25,000) or as a statement (e.g., 1 cm to 250 m). A large-scale map shows a small area in lots of detail; a small-scale map shows a large area with less detail.
地图比例尺告诉你地图上的距离与地面实际距离之间的关系。它可以用比率表示（例如 1:25,000），也可以用文字描述（例如图上 1 厘米代表实地 250 米）。大比例尺地图详细地展示小片区域；小比例尺地图以较少细节展示大范围区域。
2. Measuring Straight-Line Distance | 测量直线距离
Use a ruler to measure the distance between two points on the map in centimetres. Then multiply by the scale factor to find the real distance. For example, on a 1:50,000 map, 1 cm = 50,000 cm, which equals 500 m or 0.5 km. So if two points are 4 cm apart on the map, the real straight-line distance is 4 × 0.5 = 2 km.
用直尺在地图上测量两点之间的距离，单位为厘米。然后乘以比例尺系数，求出实际距离。例如，在 1:50,000 的地图上，1 cm = 50,000 cm，等于 500 m 或 0.5 km。因此，如果地图上两点相距 4 cm，则实际直线距离为 4 × 0.5 = 2 km。
- Real distance (km) = Map distance (cm) × (Scale number ÷ 100,000)
- 实际距离 (km) = 图上距离 (cm) × (比例尺分母 ÷ 100,000)
3. Six-Figure Grid References | 六位网格坐标
A six-figure grid reference pinpoints a location within a 100 m × 100 m square on an Ordnance Survey map. The first three figures are the eastings (along the corridor), and the last three figures are the northings (up the stairs). To give the third and sixth figures, imagine each grid square divided into ten equal parts along the bottom and side.
六位网格坐标可在 Ordnance Survey 地图上精确定位 100 m × 100 m 方格内的一个地点。前三位数字是东向线（沿横向走廊读数），后三位数字是北向线（沿纵向楼梯向上读数）。为了给出第三位和第六位数字，可以将每个网格方格沿底边和侧边均分为十等份。
The formula for remembering the order: Eastings first, then Northings. For example, reference 123456 means the point is in easting square 12, 3/10 across the square, and northing square 45, 6/10 up the square.
记忆顺序的公式：先读东向，后读北向。例如，坐标 123456 表示该点位于东向方格 12、距方格左侧 3/10 处，北向方格 45、距方格底边 6/10 处。
4. Compass Bearings and Direction | 罗盘方位角与方向
A compass bearing is the angle measured clockwise from north. It is always given as three figures (e.g., 045°, 180°, 315°). North is 000° or 360°, East is 090°, South is 180°, and West is 270°.
罗盘方位角是从正北顺时针测量的角度。它始终用三位数字表示（例如 045°、180°、315°）。正北为 000° 或 360°，正东 090°，正南 180°，正西 270°。
To find a bearing on a map, draw a line from the start point to the destination, place the protractor with 0° pointing grid north, and read the angle clockwise.
要在地图上测定方位角，从起点向目的地画一条线，将量角器的 0° 对准网格北，然后读取顺时针角度。
5. Contour Lines and Relief | 等高线与地形
Contour lines join points of equal height above sea level. The contour interval is the vertical difference between two neighbouring contour lines. Closely spaced contours mean a steep slope; widely spaced contours indicate a gentle slope. Concentric contours with higher values towards the centre usually represent a hill or mountain.
等高线连接海拔高度相同的各点。等高距是相邻两条等高线之间的垂直高差。等高线密集表示陡坡；等高线稀疏表示缓坡。向中心数值增大的同心等高线通常代表山或丘陵。
To calculate the height difference: Height difference = Highest contour – Lowest contour. Be sure to check the contour interval on the map key.
计算高差：高差 = 最高等高线数值 – 最低等高线数值。务必查看图例中的等高距标示。
6. Slope Gradient | 坡度计算
Gradient compares the vertical rise of the land to the horizontal distance covered. The formula is:
坡度比较了地面的垂直升高与水平行进距离之间的关系。公式为：
Gradient = Vertical Height ÷ Horizontal Distance
坡度 = 垂直高度 ÷ 水平距离
Both measurements must be in the same unit (e.g., metres). A gradient of 1 in 10 means that for every 10 metres walked horizontally, you go up (or down) 1 metre. You will often see it written as 1:10.
两者必须使用相同单位（例如米）。坡度为 1 in 10 表示每水平行走 10 米，高度上升（或下降）1 米。通常写作 1:10。
To find horizontal distance from a map: measure the straight-line distance between the two contour lines, using the scale to convert to metres.
从地图求水平距离的方法：测量两条等高线之间的直线距离，利用比例尺换算为米。
7. Population Density | 人口密度
Population density tells you how crowded a place is. It is the average number of people living in a square kilometre.
人口密度告诉你一个地方有多拥挤。它是平均每平方千米居住的人口数量。
Population Density = Total Population ÷ Total Area (km²)
人口密度 = 总人口 ÷ 总面积 (km²)
For example, if a country has 50 million people and an area of 500,000 km², its density is 50,000,000 ÷ 500,000 = 100 people per km². Densely populated areas have a high figure; sparsely populated areas have a low figure.
例如，某国有 5000 万人口，面积为 500,000 km²，其密度为 50,000,000 ÷ 500,000 = 100 人/km²。人口稠密区的数值高；人口稀少区的数值低。
8. River Discharge and Velocity | 河流流量与流速
Discharge is the volume of water flowing past a point in a river each second. It is measured in cubic metres per second (cumecs). The formula is:
流量是每秒钟流经河流某一点的水的体积，单位为立方米每秒 (cumecs)。公式为：
Discharge (Q) = Cross-Sectional Area (A) × Velocity (V)
流量 (Q) = 横截面积 (A) × 流速 (V)
Cross-sectional area is the width of the river multiplied by the average depth. Velocity is often measured by timing a float over a known distance (distance ÷ time).
横截面积是河宽乘以平均水深。流速通常通过测量浮标漂过已知距离的时间求得（距离 ÷ 时间）。
In Year 7, you may also need to calculate infiltration rate (volume of water absorbed per unit of time) or precipitation total by simple addition.
七年级可能还需通过简单加法计算下渗率（单位时间内吸收的水量）或降水总量。
9. Climate Averages: Temperature and Precipitation | 气候平均值：气温与降水
A climate graph shows average monthly temperature (as a line) and precipitation (as bars). To calculate the mean annual temperature, add all 12 monthly averages and divide by 12.
气候图以折线展示月平均气温，以柱状图展示降水量。要计算年平均气温，将 12 个月的月平均值相加后除以 12。
Mean Annual Temperature = Sum of 12 monthly averages ÷ 12
年平均气温 = 12 个月平均值之和 ÷ 12
For total annual precipitation, simply add the precipitation for each month together.
对于年降水总量，只需将各月的降水量相加即可。
Temperature range is the difference between the hottest month and the coldest month averages. Range = Highest average – Lowest average.
气温年较差是最热月与最冷月平均气温之差。年较差 = 最高月均值 – 最低月均值。
10. Data Presentation: Chart Types and Rules | 数据展示：图表类型与规则
Different charts are chosen for different data types. Always label axes, give a title, and include a key if needed.
不同的数据类型选择不同的图表。务必标注坐标轴、给出标题，必要时附上图例。
| Chart type 图表类型 | Used for 用途 | Key rule 关键规则 |
|---|---|---|
| Bar chart 柱状图 | Comparing categories 比较类别 | Bars same width, gaps between bars 柱宽一致，柱间留间隙 |
| Line graph 折线图 | Showing change over time 显示随时间的变化 | Points joined by straight lines 用直线连接各点 |
| Pie chart 饼图 | Parts of a whole 显示部分与整体的关系 | Sectors add to 100% 各扇区总和 100% |
| Scatter graph 散点图 | Relationship between two sets of data 两组数据之间的关系 | Draw line of best fit 绘制最佳拟合线 |
11. Natural Increase and Population Change | 自然增长与人口变化
The natural increase of a population is found by subtracting the death rate from the birth rate. This gives you a percentage.
人口自然增长率通过出生率减去死亡率求得，结果以百分比表示。
Natural Increase (%) = (Birth Rate – Death Rate) / 10
自然增长率 (%) = (出生率 – 死亡率) / 10
Birth rate and death rate are usually given as per 1,000 people per year. So if birth rate is 20 per 1,000 and death rate is 8 per 1,000, the natural increase is (20 – 8) = 12 per 1,000, or 1.2%.
出生率和死亡率通常以每千人每年的数量给出。因此，如果出生率为 20‰，死亡率为 8‰，自然增长率为 (20 – 8) = 12‰，即 1.2%。
Total population change also includes net migration (immigrants minus emigrants).
总人口变化还包括净迁移（入境移民减去出境移民）。
12. Urbanisation Rate and Settlement Patterns | 城市化率与聚落模式
The urbanisation rate measures how quickly the proportion of people living in urban areas is growing. The percentage urban is:
城市化率衡量城市人口比例的增长速度。城市人口百分比的计算公式为：
Urban Population (%) = (Urban Population ÷ Total Population) × 100
城市人口百分比 = (城市人口 ÷ 总人口) × 100
When studying settlement patterns, remember the relationship between services and threshold population. A high-order service (like a hospital) needs a larger threshold population than a low-order service (like a corner shop). This is more a concept than a formula, but it helps explain why some settlements grow.
在研究聚落模式时，记住服务与其门槛人口之间的关系。高等级服务（如医院）需要的门槛人口大于低等级服务（如街角小店）。这更是一个概念而非公式，但有助于解释某些聚落为何会发展壮大。
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