3. Examples

Although we carried an additional digit in all previous computations, we'll carry a few more extra here. We'll discuss the area error at the end of the chapter but for now we want to over-compute the area accuracy then report it to an appropriate resolution after we analyze it. If we don't carry additional digits, we could easily increase error due to rounding. To be on the safe side, we'll carry the computations to 0.1 which should be less than the expected error.

a. Example 1

Figure G-7 is a continuation of the Bearing Traverse example we have been using in the past few chapters.

	Point North (ft) East (ft) A 500.000 2000.000 B 323.614 1561.426 C 526.996 1488.321 D 719.336 1686.956
Figure G-7 Example 1 Traverse

 Step (1) Start at point A and going clockwise around the traverse list the coordinates:

Step (2) Cross multiply in one direction:

Step (3) Cross multiply in the other direction

Point	N (ft)	E (ft)	(), sq ft	(), sq ft
A	500.000	2000.000	647,228.0
B	323.614	1561.426	822,865.2	780,713.0
C	526.996	1488.321	1,070,602.9	481,641.5
D	719.336	1686.956	843,478.0	889,019.1
A	500.000	2000.000		1,438,672.0

Step (4) Add up the columns

Step (5) Using Equation G-3 compute the area

Until we discuss area accuracy more fully, we'll state the area as 102,935.8 sq ft.

There's nothing magical or sacred about point A. We could have stated our list at point C and traveled counter-clockwise around the traverse. As long as we remember to repeat the initial point at the bottom of the list, we will come up with the same area although one could be positive and the other negative.

b. Example 2

Figure G-8 shows the Crossing Traverse we've been using as another running example.

With a crossing traverse, one must be careful when listing the coordinates. In this case, if you list the coordinates along the original traverse path, E-F-G-H-E, you will be able to compute an area but it will be nonsensical. The traverse turns itself inside out.

Recall that this survey was on a four-sided parcel having two obstructed lines, Figure G-9.

We want the the area of the parcel, not the traverse.

Step (1) Start at point E and going clockwise around the parcel, list the coordinates.

Step (2)-(4) Cross multiply in both directions; sum the columns.

Step (5) Use Equation (G-3) to compute the area