RW05 — Comparison of Google Earth and Coordinate-Based Area Determination - Report

RW05 — Comparison of Google Earth and Coordinate-Based Area Determination

Research Work Record

Item	Record
Student	Juan Dela Cruz
Site	Training Site A
Digital Method	Google Earth polygon measurement
Computational Method	Coordinate / shoelace area
Submission	Handwritten computations with printed Google Earth figure

Compared Results

Method	Area (m²)	Area (ha)
Google Earth polygon	18,640	1.8640
Coordinate computation	18,575	1.8575

Absolute difference:

\Delta A=|18{,}640-18{,}575|=65\text{ m}^2

Percentage difference relative to the coordinate result:

\%\Delta=\frac{65}{18{,}575}(100)=0.350\%

Coordinate-Area Computation Record

Vertex	Easting, x (m)	Northing, y (m)	$x_i y_{i+1}$	$y_i x_{i+1}$
P1	1000.0	1000.0	1,120,000	1,000,000
P2	1120.0	1000.0	1,198,400	1,070,000
P3	1198.4	1070.0	1,300,264	1,145,000
P4	1215.2	1085.0	1,150,799	1,111,850
P5	1060.0	1055.0	1,060,000	1,055,000

The complete handwritten solution should show the closed vertex sequence and both shoelace sums. The table above demonstrates the required organization; values must remain internally consistent with the student's assigned dataset.

Comparison and Interpretation

Possible Source of Difference	Effect
Google Earth vertex placement	Changes polygon shape and area
Imagery resolution / perspective	Makes visible boundary interpretation approximate
Coordinate rounding	Introduces small computational differences
Different boundary definition	Can create the largest discrepancy
Terrain vs planimetric interpretation	May influence digital measurement assumptions

A 0.350% difference is small for a classroom desktop-comparison exercise, but neither method should be presented as a legal boundary determination unless the coordinates and boundary definition come from an authorized survey.

Conclusion

The digital polygon produced 18,640 m², while the coordinate-based method produced 18,575 m², a difference of 65 m² or 0.350%. The exercise demonstrates why measurement method, coordinate precision, and boundary interpretation must be stated alongside an area result.

Submission: Handwritten RW due on the next meeting with the Google Earth measurement screenshot attached.