Are you trying to figure out the exact ground resolution for your aerial or satellite images? It can be confusing to juggle altitude, pixel size, and lens details to understand what your images really mean for mapping, surveying, or research.
That’s why we built this simple Ground Resolution Distance Calculator. In this article, you’ll not only get a free tool to calculate instantly, but you’ll also learn how the formula works behind the scenes.
By the end of this page, you’ll be able to confidently calculate ground resolution distance (GRD) and make accurate, data-driven decisions for your projects.
How to Use This Calculator
- Enter Altitude (H): This is the height of the sensor above the ground.
- Input Pixel Size (p): This is the physical size of each sensor pixel.
- Add Focal Length (f): The focal length of the lens in use.
- Click Calculate: Your result, the Ground Resolution Distance, will be displayed instantly.
The Formula Explained: How It All Works
For those who like to see the mathematics, here are the formulas our calculator uses:
- Ground Resolution Distance (Nadir/Vertical View):
GRD = IFOV × H - Ground Sampling Distance (GSD):
GSD = (H × p) / f - Oblique View GRD:
GRD_oblique = GRD_nadir / cos(θ)
Variable Breakdown
- GRD: Ground Resolution Distance
- GSD: Ground Sampling Distance
- IFOV: Instantaneous Field of View (in radians)
- H: Altitude of the sensor
- f: Focal length of the lens
- p: Pixel size on the sensor
- θ: Off-nadir angle
Practical Example: Let’s Walk Through It
Let’s imagine you want to calculate the ground sampling distance for a drone survey.
Scenario Data
- Altitude (H): 120 meters
- Pixel size (p): 0.005 mm
- Focal length (f): 20 mm
Calculation
GSD = (H × p) / f
GSD = (120 × 0.005) / 20
GSD = 0.03 meters
The Result
The final result is 0.03 meters (3 cm). This means that each pixel in the captured image represents 3 cm on the ground.
Ground Resolution Distance Reference Table
| Altitude (H in meters) | Pixel Size (p in mm) | Focal Length (f in mm) | Ground Resolution Distance (GSD in meters) |
|---|---|---|---|
| 100 | 0.005 | 20 | 0.025 |
| 150 | 0.005 | 20 | 0.0375 |
| 200 | 0.005 | 20 | 0.05 |
| 300 | 0.005 | 20 | 0.075 |
| 400 | 0.005 | 20 | 0.10 |
This table helps you quickly estimate without recalculating each time.
Helpful Tips and Tricks
- Always keep units consistent to avoid errors in your calculations.
- Flying at higher altitudes increases GRD, which reduces image detail.
- Use GSD results to plan optimal flight paths for mapping and surveying.
FAQs
The accuracy depends on the precision of your input values. With correct sensor details and altitude, the results are highly reliable.
For professional mapping, a GSD of 2–5 cm per pixel is considered very good. For general surveys, 10–20 cm may be acceptable.
Check the camera’s datasheet or manufacturer’s website. These values are usually listed under the camera specifications.