Interactive Ground Sampling Distance (GSD) Calculator
Use this tool to calculate image resolution on the ground and estimate coverage footprint for drone or aerial mapping missions.
Need altitude for a target GSD?
What is Ground Sampling Distance?
Ground Sampling Distance (GSD) is the real-world distance represented by one pixel in an image. If your GSD is 2 cm/pixel, then each pixel covers a square area of roughly 2 cm by 2 cm on the ground. Smaller GSD values mean higher spatial detail, which is usually what you want for precision mapping, inspections, and measurement workflows.
Core GSD Formula
GSD (m/pixel) = Altitude (m) × Pixel Size (mm) / Focal Length (mm)
Because pixel size is often listed in micrometers (µm), convert it first:
- Pixel Size (mm) = Pixel Size (µm) ÷ 1000
- GSD (cm/pixel) = GSD (m/pixel) × 100
This calculator handles these conversions for you and reports your result in mm/pixel, cm/pixel, and m/pixel.
How to Use This Calculator
Option 1: Calculate GSD from flight settings
- Enter flight altitude above ground level.
- Enter camera focal length.
- Enter sensor pixel size.
- Optionally enter image width and height in pixels to estimate single-image footprint.
Option 2: Calculate required altitude for a target GSD
- Enter desired GSD in cm/pixel.
- Enter focal length and pixel size.
- The calculator returns required altitude in meters and feet.
Where to Get Pixel Size
Camera specs sometimes include pixel size directly. If they do not, you can estimate it from sensor width and image width:
Pixel Size (µm) = (Sensor Width in mm ÷ Image Width in pixels) × 1000
Example: a 13.2 mm wide sensor with 5472 px image width gives approximately 2.41 µm pixel size.
Typical GSD Targets by Use Case
- General orthomosaic mapping: 3-5 cm/pixel
- Construction progress and stockpiles: 1.5-3 cm/pixel
- Survey-grade detail checks: sub-2 cm/pixel (plus strong ground control)
- Agricultural scouting: 3-10 cm/pixel depending on crop stage and objective
Common Planning Mistakes
- Using altitude above sea level instead of AGL: GSD calculations should use altitude above ground.
- Ignoring slope/terrain variation: Height changes across a site can change local GSD.
- Using wrong focal length: Use actual focal length at capture, not 35mm equivalent value.
- No overlap strategy: Good GSD alone does not guarantee a good 3D model or orthomosaic.
Quick Example
Suppose you fly at 120 m AGL with a 24 mm focal length camera and 2.4 µm pixel size:
- Pixel size in mm = 2.4 ÷ 1000 = 0.0024 mm
- GSD = 120 × 0.0024 ÷ 24 = 0.012 m/pixel
- That is 1.2 cm/pixel
At this resolution, small site details are more visible than they would be at 3-5 cm/pixel.
Final Thoughts
Ground sampling distance is one of the most important planning numbers in drone mapping. Use it to match data quality to mission needs, avoid collecting too little detail, and keep flight time under control. This calculator gives you a fast way to move between camera settings, altitude, and expected ground resolution before you fly.