Geomatics Chapter 2,3
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What is the purpose of a coordinate system?
Used to define points and orientation
What are geogrpahic coordinates and how are they used?
- Used to define positionand orientation, change in location or relative distance between points on a sphere
- Based on latitude and longitude
Formed by the intersection of a plain bisection of the earth at right angles to the axis of rotation
Formed by the intersection of vertical planes passing through the center of the earth and the sphere
What is the approximate latitdue of Saskatoon?
58.1333 Degrees North
What is the approximate longitude of Saskatoon?
106.667 Degrees West
What is the approximated radius of the Earth? (Assume the Earth is a sphere)
Path made by the Earth traveling around the sun
Closest point to the sun on the ecliptic path
Farthest point from the sun on the ecliptic path
The Vernal and Autumnal equinox are points on interesection between the ecliptic and celestial equator. This plane also pass through the sun
Azimuth is the angle measured clockwise from North
Formula for calculating latitude based on the lower or upper culmination:
The interval between two successive lower transits of the sun's center of the same meridian
How long does it take for the sun to move 15 degrees?
Who proposed standard time?
International Date Line
Imaginary line that seperates two calendar dates
The interval between two successive upper transits of the vernal equinox over the same meridian
One sidereal day is equal to how many solar days?
0.9973 solar days
A nautical mile equals how many:
Minutes of arc
Branch of mathematics which determines by obsservation and measurement the exact positions of points and areas of large portions of the Earths surface, the shape and size of the earth, and the variations of terrestrial gravity
In geodetic surveying, the computation of the geodetic coordinates of points are performed on what?
Performed on an ellipse as it closely approximates the size and shape of the earth
What is the geoid?
The geoid coincides with the surface to which oceans would conform over the entire earth of free to adjust to the effects of gravity and centrifugal force
Deflection of the Vertical
The angle between a plumb line (line perpindicular to the geoid) and a line perpindicular to the ellipsoid
What does physical geodesy do?
Utilizes measurements and characteristics of the Earths gravity field to deduce the shape of the geoid
If the value of acceleration of gravity can be determined at the point of measurement directly
If only the differences in the value of the acceleration of gravity are measured between two or more points
What is the formula used for determing the orthometric elevation? What does each variable represent?
- H=Orthometric elevation
- h=Height of the ellipsoid measured from Earth's surface
- N=Geodial height (undulation)
Valuable properties of a map are:
When a map preserves shape it is said to be:
Maps that preserve areas are good for:
- Populations per square meter
- Distribution maps (trees, tons of coal etc.)
Projection at the center of the earth. All great ciircles appears as straight lines
Lambert Conformal Conic Projection
- Conical projection with two standard parallels that intersect the zone of interest at 1/6 of the zone width from the North and South zone limits
- Meridians appear as straight lines converging towards the center of the cone
Mercator Map Projection
- Projection of a globe onto a cylinder.
- Merdians are equally spaced vertical lines
- Parallels are horizontal line whose spacing increases towards the poles
- Created to show a line of constant bearing on the the globe. Appears as a straight line on the projection known as a rhumb line
What is the scale factor for a mercator map projection?
Scale at latitude=(Scale at equator) x cos(latitude)
Properties of UTM Map Projections are:
- UTM zones are 6 degrees wide
- Reference ellipsoid is NAD 27 or NAD 83
- Basis for 1:50000 topographic maps
- Origin for latitude (northing) is the equator
- Southern hemisphere given 10,000,000 as false northing at the equator
- Origin for Easting is at the Central meridian of each zone
- False Easting of 500,000 given to central meridian
- North latitude= 84 degrees N
- South latitude= 80 degrees S
At what longitude does the UTM zone numbering begin and how many zones are there?
- 180 degrees West
- 60 zones (6*60 zones = 360 degrees)
Formula for approximate elevation factor:
- Re = Radius of Earth (Sphere)
- H = Height above geoid
Formula for approximate UTM scale factor:
- k=k0+ (1+x2/2R2)
- k0 = 0.9996
- x = Easting
- R = Radius of Earth (sphere)
Formula for grid factor:
Grid Factor = (Scale Factor) x (Elevation Factor)
Formula for ground distance:
Ground distance = Grid Distance / Grid Factor
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