Toba Lake surface area measured based on the outer shoreline perimeter. Measurement using Google Earth polygon tool. Polygon tool created by click 'add polygon' tool at Google Earth toolbar. A Google Earth - New Polygon window will pop up, which named Untitled Polygon. Replace the name 'Untitled Polygon' with any name you want to tag your new polygon. Then use the mouse to create the points of the polygon perimeter. Google Earth automatically will calculated the perimeter length and the polygon area. The calculation will be showed in Measurements Tab below the polygon name. You can choose which unit will be used in the calculation. The units available are centimeters, meters, kilometers, inches, feet, yards, miles, nautical miles, smoots, degrees, arc second. Below is the image of Toba Lake polygon measurement.
The Toba Lake surface area is measured based on the points perimeter showed in the images below. The perimeter points placed at the outer shorelines of Toba Lake. The same calculation probably will have different result. The differences caused by the using of difference images for calculation, the eye altitude range and the Toba Lake surface water level. Different images will shows different time of image created and different water surface level. The eye altitude will show different details of feature in the image, the lower the eye altitude, the more details the terrain features. In this case, the measurement is did with eye altitude lower than 2 km and Toba Lake water surface is 901 m above sea level which indicated in Google Earth status bar.
Image: Toba Lake Surface Area Measurements
The measurement shows that Toba Lake outer shorelines perimeter is 370 kilometers with the area of polygon is 1.797 square kilometers. This surface area measurement value is including Samosir Island and 8 smaller islands area in Toba Lake. The calculation is the total of the surface area in the Toba Lake polygon showed in the image. To calculate Toba Lake Water Surface Area, the value of this calculation should be reduced with the sum value of all island areas in Toba Lake.
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