Measuring Land on a Satellite Map: Method and Limits

Sizing up a plot before you buy, sanity-checking the quantity a seller quotes, planning a subdivision, or estimating fencing from the perimeter — all of these are well served by tracing the boundary on satellite imagery. It is a cheap first step before paying for a ground survey.

Taking a measurement

1. Find the land

   Type the area name into the search box to move the map there, or use the locate button to jump to where you are standing.

2. Zoom in properly

   The clearer the boundary, the better the measurement. Zoom until ridges, walls, roads or tree lines are distinguishable.

3. Choose a tool

   Polygon for an area, rectangle for a regular four-sided plot, line when you only need a length.

4. Click the corners

   Place a point at each corner of the boundary. Add extra points along curves.

5. Finish

   Press Done after the last point. The area appears immediately in decimals, katha, bigha, acres and square feet.

6. Fine-tune

   Drag the white handles to adjust the boundary; the figures update as you move them.

7. Export

   Download the PDF report if you want something to take into a negotiation.

How accurate is it really

The honest answer: good, but not legal. Traced carefully at high zoom on high-resolution imagery, the area usually lands close to reality. The error comes from three places:

• Georegistration offset — satellite imagery can sit a few metres off its true ground position. On a small plot that offset is proportionally large.
• Boundary interpretation — tree shadow, scrub or cloud make it hard to place a corner exactly where the boundary is.
• Slope — map area is the horizontal projection. The true surface of steeply sloping ground is larger, although official records also generally use horizontal area.

Getting a better measurement

• Place points at maximum zoom, then zoom out to check the overall shape looks right.
• Use more points on curves. Too few points cuts corners and under-reports area.
• Trace the same plot twice. The difference between the two results is a fair estimate of your uncertainty.
• Calibrate against something known — a road width or a building whose length you can verify.
• Switch base maps. The street or terrain layer sometimes shows a boundary the imagery hides.

When only a ground survey will do

In any of these situations a map measurement is not enough and you need a licensed amin or surveyor working from the mouza map:

• A boundary dispute with a neighbour, or litigation.
• Registration, mortgage or bank lending paperwork.
• A final partition between co-owners.
• Building plan approval or setback calculations.
• A large discrepancy against the quantity stated in the record.

Frequently asked