Axle survey

This lab will introduce the concepts of calculating the field measurement adjustments (refer to lectures 8 and 9) and the introduction of coordinates from a known control to the final adjustments.
The scenario is that you have the Rusty Axle survey from lab 2
Now we are going to tie this in to a control point with the use of a control triangle survey (new field notes)
Step 1
• First compute the departure and latitudes for the control triangle
• Compute the closure error
• Adjust the triangle using adjusted Departures and Latitudes

The coordinates for the CTRL point are known so we are controlling the triangle for closure back to this point, Notice that point Atemp is also point A for the Axle survey. It should make sense then, that if we compute adjusted coordinates for Atemp, we can then transfer those coordinates to the Axle Survey

• Transfer X, Y, coordinates from the control survey to the Axle Survey
• Compute departure and latitudes for the Axle Survey (you should have this already from lab 2)
• Compute the closure error (You should have this already from lab 2)
• Adjust the survey departure and latitudes
• Compute the new coordinates

To turn in:

1. You can use a screen shot of excel spreadsheets for this if you wish. Screenshot 1 should be the control triangle adjustments and screen 2 should be the axle survey adjustments
2. Hand drawn map showing the Axle survey and the control triangle

Filed Procedures example
Lab 3 – Area Layout and coordinate computation Field Lab – Rusty Axle Traverse
Prelude
Prior to starting this lab, you should review the Powerpoint presentations on Area Layout with the Hand Compass and Length Measurement if you had difficulty with Lab 2.
This lab is an introduction to the calculations used to generate coordinates for the area layout lab and the concept of starting a traverse from a known control point. Coordinates and coordinate systems will be covered in more detail later in the course. For now, you should think of coordinates as a way of locating an area on the surface of the Earth through a series of x,y coordinates. Additional objectives include continuing to practice proper instrument use and care, and to promote good note-keeping practices.

Preliminary field work

1. Prior to starting the lab, your field book should be complete to date.
2. Lay out a similar traverse to the one in lab 2. If you still have your points marked from Lab 2 you may want to use those.
3. In addition, you need to put in a control point (CTRL) located outside of the traverse area and 100 feet or farther from your beginning point (point A or whatever you have labeled the beginning point.

Note that for this lab you will again need a “helper/assistant”

Objectives

The objectives of the day’s activities are:

1. Layout a large area with at least 6 sides as a minimum
2. Layout the control point
3. Understand how the control point establishes the coordinates for all other points on the traverse
4. Understand the concept of closure
5. Compute linear and relative errors for the traverse
6. Adjust coordinates to corrected values
7. Refine good note keeping practices
8. Refine and practice safe working practices

A. Pre-work
Read completely through the instructions for this lab before starting
You will need to locate a large playground field or a large open area that has some hills or slope to it. It should not be overly steep or brushy. You may use the traverse from Lab 2 if it is still marked.

Perform a class tailgate safety meeting at the field site. Note this in your field book. Record the following for both yourself and your helper/assistant:

1. Each person has been asked about allergies/reactions to bees or other insects
2. A first aid kit is available and everyone knows the location of it
3. Sunscreen and water are available if needed
4. Check and note cell phone coverage
5. Check that each person has all needed equipment
   a. Field book(s)A
   b. Calculator
   c. Sharpie pens
6. Check that you have all needed equipment
   a. Reel Tape
   b. Silva hand compass
   c. Clinometer
   d. Pin flags

B. Field work

Part I. Establishing your control traverse

You will be working with an assistant

1. Begin with an arbitrary point in the ground labeled CTRL. This should be 100 feet or more from your traverse starting point (see diagram below). Assign the coordinates X=1000.00’, Y=1000.00’, Z=1000.00’ to this control point.

Note that we are creating a control traverse in the form of a triangle to determine the starting coordinates for point A of our traverse. We will be correcting this control data as a beginning survey, and then creating a second survey of the traverse itself using the adjusted coordinates for point A as a control point.

2. Measure distance and direction from the CTRL point to the starting point (A) of the traverse.
3. Next, establish a new point (B) to result in a control triangle. You should have something that looks like this
4. Once the survey is complete for the control triangle, move on to Part II. The computations for both traverses will be done later in the office.

Part II. Establishing your traverse area

1. This is a repeat of lab 2 instructions for laying out the traverse. Begin at the pin flag in the ground at point A
2. From this pin flag, pace off a distance that is greater than the total tape length. For example, if your tape is 100’ in length, pace off a distance of about 150’-200’
3. Put a pin flag in at this position (point B)
4. Make a turn that is not a sharp angle
5. Pace to the next position (point C)
6. Repeat steps 3-5 until you have 6 points in the ground. Note that the last traverse point will close back to point A

Part III. Traverse computations

The following steps are used to compute the adjusted coordinates. This will be done on two procedures, one for the control triangle and the second for the traverse itself.

1. Compute departures and latitudes
2. Compute linear error
3. Compute Departure and latitude adjustments
4. Compute adjusted departures and latitudes
5. Compute adjusted coordinates

Example Field Notes for the control

Example Field Notes for the traverse

Sta SD % HD Brg Ahd Brg Bk

        1

A N25E

1217    +5  1215                                

B N65E S25W

1357    +12 1347                                

C S81E S66W

861 -10 857         

D N81W

                                    J. Smith    
                                    Original    

Example Calculations for the control

(refer to the file Lab 3 Control Calculations.PDF)

When doing the calculations for the traverse, remember to use the starting adjusted coordinates for point A

Deliverables

Complete the lab with a write up that includes:

A brief summary of the lab exercise
A brief summary of the measurements
Include the overall traverse length (horizontal distance) and survey data in table format
A scanned or Xerox copy of your field notes
A scanned copy of the calculations in the proper homework format (refer to the file Lab 3 Control Calculations.PDF)
A scale map of the traverse (see the presentation on map requirements)

Sample Solution