RW05 — Comparison of Google Earth and Coordinate-Based Area Determination
Learning Objectives
- Determine the area of one site using a Google Earth polygon.
- Compute the same site's area using an assigned coordinate-based method.
- Quantify and interpret the difference between the two results.
Activity Scope
Use the same closed boundary for both methods, document the Google Earth polygon result, compute area from the provided or derived coordinates using the assigned coordinate-area method, calculate absolute and percentage differences, and explain likely causes including imagery interpretation, coordinate source, point placement, projection, and rounding.
Comparison Limitation
The comparison is an educational accuracy and method exercise. A close numerical match does not convert imagery-derived boundaries into legal or survey-grade property boundaries.
Submission Requirement
Research Work is due on the next class meeting and is handwritten. Required Google Earth screenshots and coordinate tables may be printed and attached.
Placeholder Status
The final activity will specify the coordinate dataset, required computation method, comparison formula, and grading criteria.
RW05 — Required Data Tabulation
Use this structure as the minimum field or research data table. Add columns when the activity requires more detail.
Add a comparison table showing Google Earth area, coordinate/shoelace area, absolute difference, percent difference, perimeter if required, and an explanation of likely sources of discrepancy.
RW05 — Grading Rubric
Award points according to the evidence shown for each criterion.
| Criterion | Full-credit evidence | Points |
|---|---|---|
| Google Earth area measurement | The same site boundary is measured carefully and the digital area/perimeter result is documented with units and map evidence. | 4 |
| Coordinate-based area setup | Vertices are ordered correctly, coordinate units are consistent, and the polygon is closed correctly. | 5 |
| Shoelace/coordinate computations | Products, summations, final area, conversions, and arithmetic are correct and traceable. | 5 |
| Method comparison and error analysis | Absolute/percent differences are correct and plausible causes of discrepancy are technically discussed. | 3 |
| Handwritten presentation | Computations and discussion are handwritten, organized, legible, and supported by the required map/coordinate attachments. | 3 |
| Total | 20 / 20 | |
Scoring guide: full credit for complete, technically correct, traceable evidence; reduce proportionally for minor errors, incomplete work, or weak documentation.
Key Takeaways
- Method comparison requires the same boundary definition and consistent units.
- Differences must be quantified and technically interpreted rather than hidden.