BSCI 3300 - Field Surveying - Quiz 1 (Ch. 1-3)

public land survey system

30 US states use this; a rectangular system using meridians, latitude, and longitude

line

- lines and points on a horizontal plane; can determine the layout of the site, structure, systems or finishes

- measured in the x and y plane

grade

- elevation of any given point

- measured in the Z dimension

offset

- layout control line or point that is a known dimension off a column line, wall, or slab

- used so that we still have a line of sight once the components of the building are installed

datum

- known or commonly agreed on reference point for elevation and grade work

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benchmark

primary control used as a reference or grade for elevation work in the Z dimension

finished floor

a common datum for building construction

errors

part of the process; limitations of the human eye, limitations from mechanical instruments, and limitations from wind and weather

mistakes

typically avoidable; math errors, incorrectly transferring data, incorrectly reading measurements, or placing measurements and instruments in the wrong location

metric

most widely used measurement system around the world

imperial

used by the US; also called the standard system; we will use this

engineering units

we use this for civil work; use partial feet

pacing

most adults have a pace length of between 2.75 and 3.50 feet per pace

chain

100' or 200' fiberglass or metal tape measure; far more accurate than pacing

plumb bob

used in measuring two surfaces with different heights; gravity makes this show where the measurement should be; keep string as short as possible

outside to outside

between columns or walls

inside to inside

between stud walls, cabinets, or door frames

inside to outside

wall corners and steel framing members

centerline to centerline

center of one stud, column or footing to the center of the next one

grade rod

basically a heavy duty tape measure that supports itself vertically

control points

- references that we know some information about

- in the case of vertical control, it is the elevation that is known and we use that to lay things out in the Z dimension

mean sea level

the most used datum for vertical construction; also the primary datum for the national geodetic survey and for the reference point used for vertical layout on the construction site

builders level

most commonly used for vertical measurement and layout; used for differential leveling, which is the process of comparing elevations of two objects

three components of the builders level

tripod, level and grade rod

backsight

reference point; starting point

foresight

target point

turning point

temporary point that is closer to the point of interest when there is an obstruction; must be visible and stable; a point used when there is an obstruction between the reference point and target point

gunsight

used as a guide to point the level in the correct general direction

foot indicator

large red number of the grade rod

reminder numbers

small red number of the grade rod

black numbers and white spaces

0.1 foot intervals

how to use builders level

1. identify benchmark point and write it down in field book

2. set the rod on benchmark and take rod reading - this is the backsight and is the height of the cross hairs of the builder's level above the benchmark; the height of the instrument will be the elevation of the benchmark plus the height of the cross hairs above it

3. move rod to the point you wish to measure, rotate the builder's level until you can see the grade rod through the scope and take a reading;; this will be the foresight and it is how far below the cross hairs the object is

4. the elevation of the object will be the height of the instrument - the foresight

error of closure

(sum of the backsites) - (sum of Foresites) = should equal the beginning elevation