Unit 2 Fundamentals of Surveying

Question 1

What is the Science of Surveying

Answer 1

Surveying determines the relative location of points on or near the earth’s surface.

The science of measuring horizontal and vertical distances between objects, measuring angles between lines, determining line direction, and establishing points based on angular and linear measurements.

Question 2

What are the methods of surveying

Answer 2

Geodetic and Plane

Question 3

What is Geodetic surveying

Answer 3

Have highest precision and cover large areas. More precise instruments and procedures are required than for plane surveys.

Question 4

How are positions expressed in Geodetic surveys

Answer 4

Expressed as latitude/longitude or as Northing/Easting

Question 5

What is latitude

Answer 5

angular distance North or south of the equator

Question 6

What is longitude

Answer 6

angular distance east or west of prime meridian

Question 7

What is Plane surveying

Answer 7

Surveys we are most involved with. When extent of survey is smaller than 250 km and limited accuracy is required. Earth is assumed to be flat surface. Calculations are made using geometry and trigonometry. Examples: highway and railroad surveys considered plane surveys

Question 8

What are the types of surveying?

Answer 8

Optical and GPS

Question 9

What is Optical surveying

Answer 9

Revolves around the concept of a known position, distance, and direction. Direction is expressed in angular unit of measurement known as a degree. Degrees are broken into minutes, Minutes broken into seconds

Question 10

What tools are used for optical surveying

Answer 10

Total station and Auto-level

Question 11

What does Auto-level use to get measurements?

Answer 11

Philly Rod (determines the differences in height between objects

Question 12

What are typical optical errors?

Answer 12

Calibration, Parallax, Refraction, Prism offset, human error. Most common is human error

Question 13

What is parallax?

Answer 13

When instrument is not properly adjusted, resulting in a poor sighting of objects

Question 14

What is refraction?

Answer 14

bending of light rays which causes poor sighting or poor survey shots. Prevent by avoiding excessively long shots

Question 15

What is prism offset

Answer 15

All prisms have an offset regardless of how small, impossible for prism to sit directly over top of a point and provide 360 degree coverage

Question 16

What are common human errors

Answer 16

Fat fingering buttons/numbers, improper notes, not setting up job correctly

Question 17

Describe GPS Surveying

Answer 17

A passive, all weather, 24 hour Global Navigational Satellite System (GNSS) operated and maintained by the DOD. Consists of no less than 24 satellites in orbit. Ground based static or roving GPS receiver is a range measurement device. Distances measured between receiver antenna and four or more satellites in view, position determined from the adjusted intersections of the signals.

Question 18

What are the three segments of GPS

Answer 18

space segment, control, user segment

Question 19

What does space segment of GPS Surveying consist of?

Answer 19

Designed with four satellites in each of six orbital planes inclined at 55 degrees to the equator. Number of satellites varies on time of day and their locations. Satellites are 20,200 km altitude and have 11 hour 58 min orbital periods.

Question 20

What space satellite systems are available?

Answer 20

GNSS (USA), GLONASS (Russia), GALILEO (Europe), CNSS (China)

Question 21

Describe the Control Segment of GPS surveying

Answer 21

Consists of Master Control Station and six monitoring stations located throughout the world. Master Control Station located in Schriever AFB, CO. Backup station is located in Vandenburg AFB, CA. Info from monitoring stations that track satellites is used in controlling the satellites and predicting their orbits. All data from tracking stations are transmitted to Master Control Station. Ephemerides, clock corrections, and other message data are then transmitted back to monitoring stations. Ephemeris data used to calculate precisely where the satellite was at the start of message. GPS almanac is also transmitted which includes health of entire GPS satellite constellation.

Question 22

Describe User Segment of GPS Surveying

Answer 22

Represents the ground based GPS receiver units that process the GPS satellite signals and compute the position and/or velocity of the user.

Question 23

What are typical GPS Errors?

Answer 23

Multipath, Position dilution of Precision (PDOP), Atmospheric effects, Human Error

Question 24

What is multipath

Answer 24

when GPS signal (ephemeris) is reflects off a hard object such as building or car. Causing error due to signal not following direct path

Question 25

What is PDOP

Answer 25

when satellites are all clustered in one location in the sky. Causes poor triangulation

Question 26

What are Atmospheric Effects

Answer 26

Can delay and distort the ephemeris (GPS Signal). Ionosphere contains many electrically charged particles that causes GPS signal to be reflected. Troposphere holds water molecules which causes signal to be reflected

Question 27

What are GPS human errors

Answer 27

Fat fingering, inputting wrong data, not taking enough observations to calculate accurate point

Question 28

What is a datum

Answer 28

Point of origin

Question 29

What are the two types of datums

Answer 29

local and geocentric

Question 30

What is local datum

Answer 30

Reference point that is situated on the earth surface with the ellipsoid or geoid being referenced around that. Local datums are more accurate

Question 31

What is Geocentric Datum

Answer 31

Reference point is the center mass of Earth

Question 32

What horizontal datum does the US use?

Answer 32

NAD 83

Question 33

What vertical datum does the US use?

Answer 33

NAVD 88

Question 34

What datum is tied to GPS and used by DOD and defined by NGA

Answer 34

WGS 84

Question 35

What is a geoid model

Answer 35

Accounts for the differences between the ellipsoid shape and the actual shape of the earth. Geoid is defined as the hypothetical shape of the Earth's surface at mean sea level. It is perpendicular to the direction of gravity pull

Question 36

What is ellipsoid

Answer 36

Also known as spheroid. Ellipsoid has a center, or datum, to which the ellipsoid is referenced from. Geoid is irregular shape which makes calculating distances/angles difficult. SMWs created work around using mathematical shape to best represent the shape of earth using an ellipsoid.

Question 37

What are Coordinate Grid Systems (GCS)

Answer 37

Uses 3-D spherical surface to define locations on the earth. Datums are part of a GCS. GCS includes angular unit of measure, a prime meridian, and a datum. Lat and Long are considered a GCS.

Question 38

What is projected coordinate system

Answer 38

Defined on a flat, 2-D surface. Has constant lengths, angles, and areas across the two dimensions. Always based on a GCS that is sphere or spheroid

Question 39

What is Universal Transverse Mercator Coordinate system?

Answer 39

UTM is a projected coordinate system using Cartesian coordinates. Divides the earth into 60 zones by longitude (vertical) lines. Each zone has its own Cartesian coordinate system independent of other zones. UTM is military's primary coordinate system.

Question 40

What is MGRS?

Answer 40

Grid reference system based upon the UTM coordinate system and its zones. Used by NATO to reference earth.

Question 41

What is Continuously Operating Reference Systems (CORS)?

Answer 41

Used to correct data for GPS surveys. Comprised of several sub networks operated by more than 200 organizations

Question 42

Define accuracy per surveys

Answer 42

closeness of a measured value to a standard or known value

Question 43

Define precision per survey

Answer 43

closeness of two or more measurements to each other

Question 44

What is order of accuracy

Answer 44

Specifications are based on the minimum degree of accuracy allowed for a particular survey, and the range between the allowed degrees is called the order of accuracy. Measurements for first order accuracy surveys are most accurate. Construction surveys require a minimum 3rd order of accuracy

Question 45

Describe high order surveys

Answer 45

Surveys requiring accuracies of First Order (1:100,000) or better should be performed using FGDC geodetic standards and specifications. These Surveys must be adjusted or evaluated by NGS if official certification relative to the national network is required.