Spherical geometry is the geometry of the two-dimensional surface of a sphere.
34
votes
5answers
3k views
Why is the 'straight line' path across continent so curved?
This is the result of mapping the straight line path from a point in US to Poland using Distance Measurement Tool.
Also, planes from Asia to US would travel almost over North Pole.
Why is the path ...
21
votes
3answers
12k views
Algorithm for offsetting a latitude/longitude by some amount of meters
I'm looking for an algorithm which when given a latitude and longitude pair and a vector translation in meters in Cartesian coordinates (x,y) would give me a new coordinate. Sort of like a reverse ...
15
votes
3answers
5k views
Why is law of cosines more preferable than haversine when calculating distance between two latitude-longitude points?
In fact, when Sinnott published the
haversine formula, computational
precision was limited. Nowadays,
JavaScript (and most modern computers
& languages) use IEEE 754 64-bit
...
14
votes
1answer
499 views
How accurate is approximating the Earth as sphere?
What level of error do I encounter when approximating the earth as a sphere? Specifically, when dealing with the location of points and, for example, the great circle distances between them.
Are ...
9
votes
1answer
258 views
How to visualize azimuthal data with uncertainties?
I am trying to make a figure showing azimuthal data with a different range of uncertainties at each point. This oldschool figure from a 1991 paper captures the "bowtie plot" idea that I'm aiming for:
...
10
votes
3answers
654 views
How to calculate the visible sky percentage
Hi I am writing a project and I am stuck: can anyone explain as simply as possible how to calculate the visible sky percentage?
I have done a satellite survey and have worked out the height of ...
11
votes
2answers
796 views
Calculate distortion outside a UTM zone
One of my colleagues is working with data that is spread across two UTM zone. The majority of the data is in one zone, with a few outliers in another zone. He would like to know what the area ...
9
votes
3answers
634 views
How can I find the most remote spot in Eastern United States?
I have this hunch that I could travel no more than 50 miles from the most remote spot in the Eastern United States (east of the Mississippi River), in the direction of the nearest road, and find a ...
6
votes
3answers
1k views
How to find a point half way between two other points?
I'm working on implementing the OSM Mobile Binary format for map data, and because it uses a 16 bit delta for each point along a way, it cannot represent a way if there is a large distance between two ...
5
votes
2answers
2k views
How to convert Distance, Azimuth, Dip to XYZ?
I have an excel spreadsheet with header and survey drill data. Header data contains hole ID, and location coordinates, and the survey data contains related downhole survey with Distance, Azimuth and ...
12
votes
2answers
276 views
Bilateration - Intersection of 2 Circles
I'm trying to figure out how to mathematically derive the common points of two intersecting circles on earth's surface given a center Lat/Lon and a radius for each point.
Ex.
Given:
Lat/Lon ...
5
votes
2answers
414 views
Identify the latitudinal and longitudinal point directly beneath an object in space
Given the azimuth and altitude / latitude and longitude from the observer to the satellite, how can I accurately find the latitude and longitude of the point of intersection directly under the ...
4
votes
2answers
294 views
How to calculate area of 1 x 1 degree cells in a raster
I have a simple array (not geo-referenced in any way) in Matlab (which is not a language I know a huge amount about...so I can export it to other languages if needed) which has the dimensions 180 x ...
3
votes
2answers
416 views
How do I find the points of intersection between a small circle and a great circle?
I only actually need to intersect a great circle arc i.e. the shortest path between two points, with a given small circle.
I found this tutorial for intersecting two great circle arcs, but ...
5
votes
1answer
605 views
Find tangent point on circle furthest east or west
There are few ways of articulating my question. It starts with a known circle on a sphere, i.e. a point-radius, and one that does not cover a pole. I would like to calculate the point furthest west ...
8
votes
1answer
378 views
Given a line on the earth's surface, how do I plot a line perpendicular to it?
Given a line on the earth's surface, how do I plot a line perpendicular to it?
Apologies if this is a very simple question. I thought this would be a straightforward task, but it is proving ...
10
votes
2answers
1k views
Lon/lat transformation
First I should clarify I don't have previous experience with the field, so I don't know the technical terminology. My question is as follows:
I have two weather datasets:
The first one has the ...
7
votes
1answer
510 views
How does one calculate an angle in a geographic coordinate system?
Given three points on a line in a geographic coordinate system, how does one calculate the angle formed by these three points?
Please, give a general solution but also include system specific ...
5
votes
2answers
222 views
Does the Chamberlin trimetric projection map (some) great circles to straight lines?
I know that, in general, the Chamberlin trimetric projection maps most great circles on the sphere to some sort of non-straight curve on the flat map.
But what about the 3 special great circles ...
5
votes
2answers
535 views
Quick way to determine if facing a given lat/lon pair with a heading
I'm looking for a fast way, preferably without trigonometric operations (just multiply, divide, add, sqrt and subtract) to determine if a point is visible. E.g. say I am facing 0 degrees N, I am at ...
4
votes
1answer
276 views
Line intersection with circle on a sphere (globe or earth)
How can I find the intersection point of a line and a circle on a sphere (on earth)
Please, if any one knows a good solution help.
Thanks in response :)
3
votes
1answer
121 views
How to calculate midpoint given north/south latitude and east/west longitude?
First, sorry if this questions sound very simple. I am very new to GIS.
Given four values of north/south latitude, east/west longitude how to calculate the center point that is correct for all cases ...
3
votes
1answer
2k views
Lat/Lon/Alt to spherical or cartesian coordinates
On my previous question, it was advised I convert lat/lon/altitude to spherical or Cartesian coordinates. I'm not working near the poles and it would be safe to assume a spherical earth. What would be ...
0
votes
2answers
3k views
How to convert lat long to meters using Mercator projection in C#
I have set of lat long values and I want their equivalent in meters using Mercator projection in C#. Can you please post some sample code or api example of some library that does exactly this?
