Topic 02 pt 2

Question 1

geoid

Answer 1

equipotential surface
gravity measurements
variations in mean sea level
rises under continents and lowers under oceans generally

trying to model mathematically

constantly changing

Question 2

ellipsoid

Answer 2

regualr geometric shape used to approximate the geoid

semi - minor axis (Y)

semi-major axis (X)

Question 3

NAD27

Answer 3

describes Clark 1866 ellipsoid
was latered to maximize NA
based entirely on ground surveys
lots of distortions built into it

local datum

Question 4

NAd 83, WGS84

Answer 4

almost identical, growing further apart

both shared GRS80 ellipsoid, but origin differs by about 2,=m

Question 5

what is the best fitting ellipsoid

Answer 5

WGS84

Question 6

datums

Answer 6

not just the ellipsoid (is geometric shape)

size of ellipsoid

position of ellipsoid relative to earth

two types

ECEF
Not ECEF

Question 7

ECEF

Answer 7

global datum (doesnt move)

Question 8

Not ECEF

Answer 8

local datums for specific regions

moves

plate-fixed

Question 9

horizontal datums

Answer 9

NAD 27

clark 1866

Not ECEF

Question 10

NAD83

Answer 10

GRS80

plate-fixed
almost ECEF

Question 11

WGS84

Answer 11

World geodetic model
ECEF
slight change from NAd 83

Question 12

ECEF vs plate fixed

Answer 12

ECEF
location of permanent flag would change locations

plate fixed
changes alongside with the flag location so coordinates don’t change

Question 13

ITRS

Answer 13

international terrestrial reference system
procedures and standards

Question 14

ITRF

Answer 14

international terrestrial reference frames

reference frames
realization of the procedures
describes regulations for measuring the earth

Question 15

realizations of WGS84 since original data

Answer 15

in weeks EPOCH

Question 16

EPSG

Answer 16

european petroleum survey group

codes on realizations

Question 17

GCS

Answer 17

combinations of datum and how we put lat/long on that datum
arbitrary starting starting point at the equator

Question 18

vertical datums

Answer 18

NAVD88

CGUD2013

GNSS

Question 19

NAVD88

Answer 19

supplement for the NAVD29
vertical datum

Question 20

CGUD2013

Answer 20

used in canada
provides the separation between NAD83 (CSRS)

Question 21

GNSS

Answer 21

based on ellipsoid, not sea level measurements

Question 22

calculating heights

Answer 22

getting elevation above ellipsoid not the sea level

H = orthometric height
h = ellipsoid height
N = geoid height
(changes, correction factor)

H = h - N

Question 23

CSRS

Answer 23

collection of standards, protocols, models etc

all the things that go into geospatial positioning

Question 24

NAD83 (original)

Answer 24

pretty much the same as the NAD27

ground based

static

Question 25

NAD83 (CSRS)

Answer 25

based on satellite 3d dynamic realization `

Question 26

NAD83 coordinate transformations

Answer 26

transformations between NAD83 (CSRS) to ITRF NTV2

Question 27

grid shift lines

Answer 27

grid cells where distortions are similar and has a distinct correction factor density grid in urban areas to be more precise

Question 28

NTV2 (NAD27 - NAD83 original)

Answer 28

6.1m Lat distortion 70m Long in calgary

Question 29

NTV2 (NAD83 original - NAD83 (CSRS 2010 Alberta)

Answer 29

4cm lat 6cm long

Question 30

GPS -H

Answer 30

vertical datums convert between ellipsoid height to height of geoid based on gravitational model CGVD2013 (difference of 16m)

Question 31

Choice of a map projection

Answer 31

based on type of distortions that are acceptable go by desired properties how much error exists within each projection (IE scale factor)