giscourses.cfans.umn.educogo coordinate geometry cogo involves directly entering the …direct data...
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Direct Data Entry
•COGO – Coordinate geometry
•COGO involves directly entering the
coordinates measured in the field,
•Coordinates may be tagged with attribute data
in the field, e.g. well depth or pressure, when
their locations are measured
Survey instrument for collection of
coordinate geometry data
Theodolite or Transit –
measurement of horizontal and
vertical angles
Level – measurement of vertical
angles
Electronic Distance Meter -
measurement of distance
Total Station – measurement of
angles and distances
azimuth distance X Y
p0 10128.3 6096.4
p1 32.4 122
p2 91.7 207
P3 123.3 305
P4 212.5 193
P5 273.9 206
P6 355.5 145
Given a Table of Azimuths and Distances, What are the Coordinates?
P0
P1 P2
P3
P4
P5
P6
sine (a) = A/Hcosine (a) B/Htangent (a) A/B
op
po
site
sid
e
adjacent side
Direct Data Entry
•Data then down-loaded to computer, ingested
by the GIS software, and processed to form a
spatial data layer.
•To date, surveying-based COGO has proven
too expensive for most natural resource
applications
•GPS (discussed later) increasingly common
for COGO
_____ Direction ?
_____
Degrees ?
Azimuth Angle_____
Degrees ?
_____
Degrees ?
Label direction and 0, 90, 180 and 270 Degrees
Draw a 42 degree azimuth; Draw a 256 degree azimuth
NORTH
90°
Azimuth Angle180°
270°
Label direction and 0, 90, 180 and 270 Degrees
Draw a 42 degree azimuth; Draw a 256 degree azimuth
~42°
~256°
0°
SOH - CAH - TOAIt is pronounced "so - ka - toe - ah".
SOH - CAH - TOAIt is pronounced "so - ka - toe - ah".
The SOH stands for "Sine of an angle is Opposite over Hypotenuse."The CAH stands for "Cosine of an angle is Adjacent over Hypotenuse."The TOA stands for "Tangent of an angle is Opposite over Adjacent."
http://wright.nasa.gov/airplane/trig.html
Adjacent
Op
po
site
Sine(a) = A/H
Solve for A Sine(a) x H = A
Cosine(a) = B/H
Solve for B Cosine(a) x H = B
Since you knowH (the hypotenuse or distance)And the angle “a” then
Using COGO; if given an angle and distance from a point, “PO” then calculate the coordinates of “P1”
Calculate the x, y of “P1”
Sine(a) = A/H
Solve for A Sine(a) x H = A
Cosine(a) = B/H
Solve for B Cosine(a) x H = B
Since you knowH (the hypotenuse or distance)And the angle “a” then
Use Table or Calculator
Lookup value for angle
57.6°
33.3°
Given10,128.3 = x6,096.4 = y
WORKSHEET
Lecture Question? What are the coordinates of xn, yn?
Name_____________
Background Concepts
122
65.4
103.0
65.4
103.0
57.6°
33.3°
Given xn = 10,400.6 and yn = 6,193.3, azimuth of 123.3° and distance of 305What is (xr,yr)?
305
123.3°
NEW QUESTION
-167.5
254.9
(10,655.5, 6,025.8)
57.6°
33.3°
10,334.9 6,021.6