Calculate Area Using Google Earth

Calculate area using coordinates from Google Earth

Calculate Area from Coordinates

Input Coordinates and Projected Values

Point	Latitude	Longitude	Projected X (m)	Projected Y (m)

Table of input coordinates and their local projected values used for area calculation.

What is Calculating Area Using Google Earth?

Calculate area using Google Earth refers to the process of determining the surface area of a piece of land, a body of water, or any defined region on the Earth’s surface using coordinates or features obtained from Google Earth Pro or the web version. Google Earth provides tools (like the polygon or path tool) that allow users to draw boundaries around an area of interest and get an approximate area measurement directly within the application.

Alternatively, users can extract the latitude and longitude coordinates of the vertices of the area from Google Earth and use an external calculator (like the one above) to calculate area using Google Earth data. This method can offer more control over units and sometimes allows for different calculation methods.

Who should use it?

• Land Surveyors and Planners: For initial estimations of land parcels, though professional surveys are needed for legal accuracy.
• Farmers: To estimate field sizes for planting, irrigation, and yield calculations.
• Environmental Scientists: To measure the area of forests, lakes, or areas affected by environmental changes.
• Real Estate Developers: For preliminary site assessments.
• Educators and Students: For learning about geography, mapping, and area calculations.
• Hobbyists and Homeowners: To measure their property or areas of interest.

Common misconceptions include believing the area from Google Earth is perfectly accurate for legal purposes (it’s very good but has limitations) or that it measures the true 3D surface area including terrain (it generally measures the area projected onto a reference surface unless 3D models are explicitly used and stated).

Calculate Area Using Google Earth: Formula and Mathematical Explanation

When you calculate area using Google Earth coordinates with a tool like ours, we typically convert the geographic coordinates (latitude, longitude) into a local Cartesian (x, y) coordinate system and then apply the Surveyor’s formula (also known as the Shoelace formula).

1. Coordinate Conversion: For relatively small areas, we can use an equirectangular projection centered around the centroid of the polygon. The Earth’s radius (R ≈ 6371 km) is used.
`x_i = (lon_i – lon_avg) * (pi/180) * R * cos(avg_lat * pi/180)`
`y_i = (lat_i – lat_avg) * (pi/180) * R`
where `(lat_i, lon_i)` are the coordinates of vertex i, `avg_lat` and `lon_avg` are the average latitude and longitude of the vertices.

2. Surveyor’s (Shoelace) Formula: For a polygon with vertices (x1, y1), (x2, y2), …, (xn, yn), the area is:
`Area = 0.5 * |(x1*y2 + x2*y3 + … + xn*y1) – (y1*x2 + y2*x3 + … + yn*x1)|`

3. Unit Conversion: The area is initially calculated in square meters and then converted to the user’s selected unit.

Variables Table

Variable	Meaning	Unit	Typical Range
lat_i, lon_i	Latitude and Longitude of vertex i	Degrees	Lat: -90 to +90, Lon: -180 to +180
avg_lat, lon_avg	Average Latitude and Longitude	Degrees	-90 to +90, -180 to +180
R	Earth’s mean radius	Meters	~6,371,000
x_i, y_i	Projected Cartesian coordinates	Meters	Varies based on area size
Area	Calculated area of the polygon	m², km², ha, etc.	≥ 0

For larger areas, more sophisticated methods considering the Earth’s spheroidal shape are needed for better accuracy when you calculate area using Google Earth data.

Practical Examples (Real-World Use Cases)

Example 1: Measuring a Park

Imagine you want to find the area of a local park using Google Earth. You use the polygon tool in Google Earth Pro and get the following vertices:

• 40.7829, -73.9654
• 40.7850, -73.9631
• 40.7818, -73.9598
• 40.7795, -73.9621

Entering these into the calculator and selecting “Acres”, you might get a result of around 15.3 acres. This helps in understanding the park’s size for maintenance or event planning.

Example 2: Estimating a Farm Field

A farmer wants to estimate the area of a field to calculate fertilizer needs. They get the coordinates from Google Earth:

• 36.5000, -119.5000
• 36.5000, -119.4950
• 36.4970, -119.4950
• 36.4970, -119.5000

Using the calculator with “Hectares” selected, the area might be around 14.8 hectares. This allows the farmer to calculate area using Google Earth data for agricultural planning.

How to Use This Calculate Area Using Google Earth Calculator

1. Get Coordinates: Open Google Earth (Pro or web). Use the “Add Polygon” or “Add Path” tool to outline the area you want to measure. Alternatively, add placemarks at each vertex. Copy the latitude and longitude coordinates for each vertex of your polygon. Make sure you have at least 3 points.
2. Enter Coordinates: Paste or type the coordinates into the “Coordinates (Latitude, Longitude)” box, one pair per line, separated by a comma (e.g., `34.0522, -118.2437`).
3. Select Unit: Choose the desired unit for the area result from the “Output Area Unit” dropdown menu.
4. Calculate: Click the “Calculate Area” button.
5. View Results: The calculator will display the primary result (Area in selected units), the number of vertices, average latitude, and the area in square meters. A chart and table will also show more details.
6. Copy (Optional): Click “Copy Results” to copy the main findings.

The results give you a good estimate of the area. For precise legal boundaries, a professional survey is always recommended, but for many planning and estimation purposes, this method to calculate area using Google Earth data is very useful.

Key Factors That Affect Calculate Area Using Google Earth Results

1. Accuracy of Plotted Points: How carefully you place the vertices in Google Earth directly impacts the area. Zooming in helps.
2. Number of Vertices: More vertices can better approximate a curved boundary, but too many for a simple shape don’t add much accuracy and increase input effort.
3. Size of the Area: For very large areas (hundreds of square kilometers), the simple projection used might be less accurate than methods fully accounting for Earth’s curvature (spherical excess calculations). This calculator is best for small to medium areas where the Earth can be locally approximated as flat after projection.
4. Earth’s Shape Model: Google Earth uses the WGS84 ellipsoid. Simple calculators often use a spherical model, which can introduce small errors.
5. Terrain: The area calculated is usually the area projected onto a flat or reference surface (like the ellipsoid). Hilly or mountainous terrain has a larger surface area than its flat projection. Google Earth Pro’s polygon tool sometimes shows “3D area” but that’s harder to replicate externally without elevation data.
6. Coordinate Precision: The number of decimal places in your coordinates affects precision. More decimal places provide more precise locations.
7. Projection Used: Different map projections preserve different properties (area, shape, distance). The equirectangular projection used here is simple but not equal-area over large scales.

Understanding these factors helps interpret the results when you calculate area using Google Earth data.

Frequently Asked Questions (FAQ)

How accurate is it to calculate area using Google Earth data?

It’s generally very good for estimations, often within a few percent for well-defined areas. However, it’s not survey-grade accuracy for legal purposes due to imagery resolution, how points are placed, and the underlying Earth model.

Can I calculate the area of a very large region, like a country?

While you can input the coordinates, this calculator’s method is more accurate for smaller regions (like parks, farms, small lakes). For country-sized areas, spherical geometry or equal-area projections are needed for high accuracy.

How do I get the coordinates from Google Earth?

In Google Earth Pro, use the “Add Polygon” tool, draw your shape, and in the properties/edit window, you can often see or copy the coordinates. Or, add placemarks at vertices and copy their lat/lon from the properties.

What’s the difference between the area shown in Google Earth and this calculator?

Google Earth might use more complex internal calculations or consider 3D terrain for some measurements. This calculator uses a standard formula on projected 2D coordinates derived from your input, which is very common for GIS area calculations on a reference surface.

Why do I need at least 3 points?

An area is defined by a closed shape (polygon), and the minimum number of vertices to form a closed polygon is three (a triangle).

Does the order of coordinates matter?

Yes, the coordinates should be entered in the order they appear around the perimeter of the area (either clockwise or counter-clockwise).

What if my area has curves?

You approximate curves by using more vertices along the curved boundary. The more points you use, the closer you get to the true area of the curved shape.

Can I use this for non-Earth maps?

This calculator is specifically set up with Earth’s radius for converting latitude/longitude. For other planets or flat maps with Cartesian coordinates, you’d use just the Surveyor’s formula part with x, y inputs directly.