Geodetic Surveying Flashcards
(19 cards)
What are the four reference surfaces used to determine positions on the earth?
Geoid, Ellipsoid (spheroid), plane surface, earth surface
What is the Geoid?
It is a reference surface that uses variations in gravity to approximate the earths surface.
Why is it hard to perform calculations on the Geoid?
Because its a random, non uniform shape.
What is an ellipsoid?
A mathematic approximation of the earth. It can be geocentric (earth centered) or geodetic (not earth centered)
What is a plane surface
A plane surface is the flat surface which assumes the survey area is flat over a small area.
which surface reference do most of our data collection, plane survey trig calculations, data representation and set out occur?
Plane Surface
What is a geodesic?
The shortest distance between two points on the earths surface and is part of a great circle.
Why are geodesics hard to naviate
They cross successive meridians at different angles.
What is a rhumb line? Are they the same size as geodesic lines?
A curved line that crosses each meridian at the same angle. No they are longer because they curve.
Are rhumb lines easier to navigate than Geodesics and why?
Yes, because they have constant azimuths.
What is a great circle?
The largest possible circle that can be drawn around a sphere.
What are geographical coordinates?
Longitude and Latitude
What direction does longitude go?
from north to south
What direction does latitude go?
east to west.
Known as _____ what of longitude?
meridians of longitude
known as ______ what of latitude?
parallels of latitude.
What value does longitude start at, what does it finish at, and where is the prime meridian?
Prime meridian in line over Greenwich in England. The prime meridian starts at 0 degrees, and goes east or west 180 degrees.
What value does latitude start at, what does it finish at, and what is its origin.
Latitude is parallel to the equator and moves north or south. Latitude ranges from 0 degrees at the equator to +90 north or -90 south.
