1) Definitions Surveying – the art of measuring distance and angles on or near the surface of the earth
Plane surveying – the land surface is considered to be a plane for all X and Y dimensions, and all Z dimensions (height) are referenced to this plane. Most engineering surveys are plane surveys, those that cover long distances may need to correct for the earth’s curvature.
2) Equipment notebook – record all your data and sketches transit – used to establish straight lines and measure horizontal and vertical angles tape – measures distances
level rod – measures distances in elevation
total station – electronic measuring instrument that records and processes field data.
prism rod – locates the points of interest and reflect laser back to total station for angle and distance measurements.
engineer’s tape – measures the height of the instrument (transit or total station)
survey nails – locate points of interest for future use
two-way radios – keeps contact between the instrument person and the rod person
2.1)Notebook
One of the most important aspects of surveying is taking accurate, neat, legible, and complete field notes. The degree of completeness comes from practice.
Details that seem obvious in the field may be obscure back in the office a couple weeks later.
Sketches of your surveyed area will also aid in comprehension and ordering of the data.
These sketches do not need to be to scale. Do not crowd your notes.
At a minimum, ALWAYS record the instrument height, rod height, occupying point, backsight point, and datapoint ranges in your notebook.
Then, if there was an error in inputting the correct data into your total station, you have a double check.
A description and sketch of each surveyed point are very useful as well.
2.2)Level Transit
we can determine the elevation difference between Points 1 and 2 as such:
Reading on Level Rod 1 from
horizontal line of sight = 2.63 ft
Reading on Level Rod 2 from
horizontal line of sight = 7.21 ft
Elevation Difference = 4.58 ft
The distance between the points can be determined with a measuring tape.
If elevation at the instrument is known:
Actual Elevation at Point 2 = Elev at instrument + HI + LR1 Reading – LR2 Reading
If elevation at Point 1 (backsight) is known:
Actual Elevation at Point 2 = Elev at Pt 1 + LR1 Reading – LR2 Reading
2.3 Total Stations
A total station records and processes all the data collected in the field. It measures distances and angles by use of a laser shot from the instrument and reflecting prism on the survey rod. A total station is simply a computer. It can only know what you input. When you orient the total station with a 3-D location and an angle at each setup, it will reference all ensuing point data to that.
2.3) Location
If there is a benchmark available that has known XYZ coordinates, then great, use that as a setup or backsight point. Most sites that EWB work in will not have benchmarks. You have two other options, and the choice depends on the level of detail needed in your survey. If precise detail is needed, bring an accurate GPS system with you to locate your position. If relative detail is needed, then enter any value for your location and reference everything to that point, i.e. label your northing as 5000, easting as 10,000, and elevation as 1000. If the precise coordinates are not necessary, this latter option may be easier to perform in the field. *)Angle Just giving your total station a location lets it know where it is, but it doesn’t know where it’s looking. So, you will have to orient the instrument as well. The options for doing this again depend on the level of precision needed for the project. For accuracy and precision, you can either bring a compass that tells you which direction is true north, or you can shoot a second point that has known XYZ coordinates. Again, this latter one will be very rare in most EWB locations. If you bring a compass, then station your prism rod in the direction of true north and shoot with the total station. The instrument will then know where it is and where it is looking. If precision is not necessary, you can make an educated guess as the direction of north (without the aid of a compass) and shoot the prism rod. This will at least orient your instrument and the rest of your points will be referenced to this location and direction.
2.4) Leveling
For each setup, the survey instrument must be level. The locations and orientation
established above assume a level instrument. The basic procedure for tripod and instrument leveling is provided below:
1. Center tripod over desired point at an appropriate height and make the base fairly level
2. Attach the instrument to the base screw (Note: Do not let go of instrument until the bottom screw has been attached)
3. Turn on the instrument if using a total station
4. Turn on the laser level or attach plumb
5. Maneuver the tripod to center the plumb on the control point
6. Coarse-level the instrument by adjust the tripod legs individually until the level bubble is mostly centered (Note: this adjustment will only minimally adjust the location of the plumb)
7. To fine-tune the leveling, orient the three black fine-tune level knobs (at base of instrument) as a triangle with a point facing away from you
a. Adjusting the two closest to you at the same time, turning them both inward will move the bubble to the left. Turning them both outwards will move the bubble to the right.
b. Adjusting the knob away from you, turning it counter-clockwise will move the bubble away from you. Turning it clockwise will move it towards you.
8. After instrument is level, check location of plumb. If you are within a couple of inches, you may move the instrument by half-unscrewing the bottom screw and sliding the instrument into place. If you are too far off, then you will have to move the whole tripod into position.
9. Repeat until the instrument is level and over the correct point.
2.5) View scope Orientation If you are using a total station, sometimes it may not be obvious as which way is up for the survey gun. The correct orientation has the horizontal fine- tune knob on the lower right and the vertical fine-tune knob on the upper left as you are sighting through the instrument. Running the instrument upside-down will invalidate your data.
2.6)Moving the Instrument
When you shoot a point to use as your next location, place a nail or some other relatively stable marker in the ground. Move the instrument to the new nail. When setting up the total station, tell the instrument which point you are on. Since you have already shot this point, it knows its location. Backsight to another control point, and the instrument will now be correctly oriented and ready to continue on. Be sure to check your error after the backsight. If it is large, there might have been a mistake in some previous measurement that you’ll need to double check.
3) Point Descriptions Be consistent with point descriptions. Label all your control points the same, i.e. do not label them as “control1”, “control2”, etc. Label them all as “control” (or some variation thereof) and let the point ID number be the differentiating factor between them.
The importance of these distinctions will become apparent if you are using a CAD program afterwards to draw up your survey points, since each point descriptions will become its own layer in the program.
0 Comments