Thursday, March 22, 2012
Calculating Land Lot Area with GPS Coordinates
As many readers are looking for a reference to calculate land lot area and perimeter with GPS coordinates data (Global Positioning System), so I create an Excel program specifically for that purpose. Download here.
Simply by writing longitude and latitude data of each vertex of a land lot, then the program will instantly calculate the area and perimeter. To avoid confusing, always use a clockwise direction to input vertex coordinates of the land lot. Counter clockwise direction will get negative result of area calculation.
In the picture below, I calculate area and perimeter of an area around National Monument (Monas, Jakarta). Picture shows GPS coordinates obtained from Google Maps. Please note that Google Maps uses latitude-longitude order.
Shown in the picture above the land lot is an irregular shaped polygon with 8 vertices (octagon). The starting point is the vertex at bottom left, then this point is also used as an end point to form a closed irregular polygon so that the program can calculate it’s area and perimeter. Total 9 GPS coordinates are written, as the starting point and end point at the same vertex. Coordinates are written in yellow cells, and they are sorted in clockwise order. On the right, there is a graph illustrating the measured polygon shape. In this example, octagonal polygon area is 231,339 square meters, and the perimeter is 1782.7 meters.
In the attached Excel workbook, there is also formula to convert GPS data with sexagesimal (degrees minutes seconds) format to become decimal format, then that decimal format will be used to calculate the area and perimeter of a land lot with irregular and regular polygon shaped.
This article is related to previous articles: calculation of polygons and calculate distance with GPS coordinates.
There are two methods for calculation of polygon area, by matrix and by rectangles. Matrix method is rather difficult to understand but the formula is simpler. And there is an article that explain about polygon perimeter calculation.