11-12

Question 1

What is intersection and resection?

Answer 1

Intersection: set up the instrument at a control point and observe the unknown point

Resection: set up the instrument at the unknown point and observe control point

BOTH TO FIND 2D COORDINATES

Question 2

Steps to find coordinate by three-point resection

Answer 2

1. Find a and c (line that facing to the known angle)
2. Find the azimuth of those line
3. Calculate the interior angle of the middle known point (B)
4. Find A+C (A+C=180-(x+y+B))
5. Find A and C (refer to page 13)
   A=arctan( (asinxsin(A+C))/(csiny+asinxcos(A+C))
   C=arctan( (csinysin(A+C))/(asinx+csinycos(A+C))
6. Calculate one angle that facing AP or BP (Line that’s connected to the unknown point)
7. Find the length of AP or BP
8. Measure the azimuth of that line
9. Calculate the departure (D=Lengthsin(az)) and latitude (L=Lengthcos(az))
10. Add the departure to the first cooridnate to find the final answer

PLEASE DO QUESTION IN PAGE 14 FOR EXERCISE

Question 3

What should we do if the Known point (A,B,C) and unknown point (P) define a circle?

Answer 3

This will have no unique solution. Thus, we have to select point B and P to lie on the same side of a line connecting points A and C

Question 4

If we have to do other observations, what are they?

Answer 4

One angle and two distances (two control points)

Two angles and one/two/three distances (three control points)

More than three control points

Question 5

Steps to find coordinates by Two-Dimensional Conformal Coordinate Transformation

Answer 5

1. Find angle of known points by arctan(deltx/delty) NOTE: 1 angle using the truth coordinate (beta) and 1 angle using the arbitrary coordinate (alfa)
2. Count the theta = alfa - beta
3. Compute scale factor
   s=(root(deltE^2 + deltN^2))/(root(deltx^2 + delty^2))
   NOTE: numerator is the truth coordinate. Denominator is arbitrary coordinate
4. Determine the X’ and Y’ ( the perpendicular to the axis line, you can pick one know point)
   X’ = sXcostheta - sYsintheta
   Y’ = sXsintheta + sYcostheta
5. Find Tx and Ty
   Tx = E - X’
   Ty = N - Y’
6. Calculate the true coordinate for the unknown point
   E= sXcostheta - sYsintheta + Tx
   N= sXsintheta + s*Ycostheta + Ty

PLEASE DO THE QUESTION PAGE 18

Question 6

What do we need for 2D conformal coordinate transformation?

Answer 6

Minimum of two control points (known points)

Question 7

Methods of measuring area

Answer 7

Field measurement
- division of the part into simple figures
- coordinates
- offset from a straight line and double meridian distance (NOT USED)
Map measurement
- NOT USED

Question 8

Triangle area formula

Answer 8

Area = root(s(s-a)(s-b)(s-c)) with s=(a+b+c)/2

Area = (absintheta)/2