The measurement and representation of the Earth, its shape and gravitational field, distances on the Earth, and coordinate systems for locating points on it including longitude and latitude.
Questions tagged [geodesy]
85 questions
9
votes
3 answers
What is the geodesic between a point and a line (geodesic between two points) on an oblate spheroid?
I found a similiar question that also asks for the distance from a point to a line but works on a sphere.
Now I'm trying to figure out the length of the geodesic line d between the given geodesic AB and the point C.
Is this the same problem as in…
oschrenk
- 251
8
votes
2 answers
Calculate average latitude / longitude
I have the array of geographical coordinates (latitude & longitude).
What is the best way to calculate average latitude and longitude?
Thanks!
romaonthego
- 183
7
votes
2 answers
Seasonal changes in hours of daylight
I will post my own answer to this question unless someone else posts the same answer first, but I am curious to know what other points of view might lead to different ways of answering it.
Temporarily (for the duration of this question) assume for…
6
votes
4 answers
Distance between two cities on Earth
Barcelona (Spain) has the coordinates (approx): $\theta = 2^\circ$, $\phi = 41^\circ$, and New York has the coordinates: $\theta = −74^\circ$, $\phi = 41^\circ$. Notice that both cities lie on the same latitude, which makes the calculations easier.…
mathinthecity
- 303
6
votes
1 answer
What property does this equation calculate?
It's pretty difficult to Google for the meaning of a formula.
This is the equation, it has to do with ellipses and GIS coordinates.
$$\nu =\frac{ a} {\sqrt{(1 - (e^2 \cdot \sin(\varphi))^2)}}$$
$a$ is an ellipsoid axis.
$\varphi$ is geodetic coord…
James
- 201
4
votes
1 answer
Point to great-circle segment distance (WGS84)
Disclaimer: This is a cross-post from stackoverflow -- the community recommended to post it here again
I want to calculate the distance from a point given by latitude and longitude to a line-segment given by two points (part of a great-circle). All…
user2033412
- 141
4
votes
0 answers
Solving geodesic problems with Euler-Lagrange equation
This is the question:
Problem B.1 Two cities - Tel-Aviv, Israel and SanDiego, CA - have the same latitude 32
◦ N, but, different
longitudes: Tel-Aviv is 34
◦
E and San-Diego is 117
◦ W.
What is the maximal distance between the great circle arc
and…
Michael Sazonov
- 239
4
votes
2 answers
How much extra sea water is needed?
We might call this the “Noah's Ark” calculation, but in the movie Waterworld (1995) they have the icecaps melting and take poetic license making the ~$220$ feet or so of sea water (one estimate I've seen – of how much the ocean would rise if all ice…
ipso
- 93
- 6
3
votes
2 answers
Different ways for calculating distance between two geodetic points give me different results
I'm trying to calculate the distance between two geodetic points in two different ways.
The points are:
A:(41.466138, 15.547839)
B:(41.467216, 15.547025)
The distance between the two points is pretty small (about 130/140 meters)
1) I have used the…
GVillani82
- 143
3
votes
1 answer
Prove that the loxodrome crosses all meridians at a constant angle
How to prove that the loxodrome (the rhumb line) crosses all meridians at a constant angle?
$$\tan\left(\frac{\pi}{4} + \frac{\psi}{2}\right) = e^{k\phi}, \quad k = \text{constant}$$
where $\psi$ is the latitude of a point on a sphere, and $\phi$…
Oleh Berehovskyi
- 209
3
votes
3 answers
Given two points with 3D coordinates, and three angle observations, how to caculate the coordinate of the third point
Given two points, $M_1(X_1,Y_1,Z_1)$ and $M_2(X_2,Y_2,Z_2)$,$P(X_p, Y_p,Z_p)$ is the unknown point. How to get the coordinates of $P$ by three angle observation .
The picture below displays the relationship between these points and…
hashtabe_0
- 33
3
votes
2 answers
Calculating longitude degrees from distance?
I need to calculate how many longitude degrees a certain distance from a point are, with the latitude held constant. Here's an illustration:
Here x represents the longitude degrees, the new point can be on either side of the starting point. I'm…
soren.qvist
- 155
3
votes
2 answers
Understanding differences in Geodetic (WGS84) to ECEF equations?
Methods suggested in this, that and there all recommend the following:
$$x = R \cos(\theta) \cos(\phi)$$
$$y = R \cos(\theta) \sin(\phi)$$
$$z = R \sin(\theta),$$
where latitude is $\theta$, longitude is $\phi$ and the Earth's approximate radius is…
pstatix
- 249
3
votes
2 answers
Distance between points on Earth
So the problem is this:
Assuming the surface of the Earth
is a sphere of circumference 40, 000 kilometers, estimate the distance between
Philadelphia and Paris.
I'm uncertain how to do this problem. I haven't done these kinds of question before,…
user482578
3
votes
1 answer
What is the metric of the grs 80 ellipsoid?
So, similarly to how a $2$-sphere has the metric, and if I understand this correctly:
$$
g_{ij} =
\begin{bmatrix}
R^2 & 0 \\
0 & R^2\sin^2\theta
\end{bmatrix}
$$
I was wondering, in geodesy, what is the metric for the GRS 80 ellipsoid currently in…
sovemp
- 133