11
votes
Accepted
Why is SQL Server 2019's STDistance Very Slightly Different Than The Vincenty Formula? (Same Up To ~0.0001km)
SQL Server's STDistance function does not compute geodesic distances. Its algorithm essentially generates straight lines in 3D, densifies them and maps them on the ellipsoid in a manner described more ...
- 3,746
7
votes
Get lat/long given current point, distance and bearing
What follows is a development of the formulas found in the Aviation Formulary by Ed Williams and in Movable Type Scripts by Chris Veness, from the formulas of spherical trigonometry, to solve the ...
- 13.2k
5
votes
Accepted
Euclidean and Geodesic Buffering in R
For most purposes it will be accurate enough to use a spherical model of the earth--and the coding will be easier and the calculations much faster.
Following suggestions by M. Kennedy in a comment, ...
- 68.9k
5
votes
Accepted
Modifying straight line segments to follow geodesic / great circle paths using QGIS?
You have to reproject every line into an azimutal equidistant projection based on one of its points, then densify the line.
Since all points of your grid are connected to three lines, you can densify ...
- 76.1k
5
votes
calculating bounding box from known centre coordinate and zoom
Assuming you are using the Web Mercator projection (Google Maps, MapBox etc), the key lies in these two equations:
where λ is the longitude in radians and φ is geodetic latitude in radians. The x and ...
- 283
5
votes
Accepted
testing if a Geodesic polygon contains a point c++
The following is a very close approximation to the right answer which
works under the assumption that the vertices of the polygon and the
point in question all lie within roughly 2000 km of each other:...
- 3,176
4
votes
Accepted
How to draw a circle in OpenLayers 2 and measure its radius dynamically?
You could try to use the move callback:
var my_polygonhandler = OpenLayers.Handler.RegularPolygon;
var polygonControl = new OpenLayers.Control.DrawFeature(circles,
my_polygonhandler, {
...
- 7,759
4
votes
Definition of "most northwesterly point" on a landmass?
Draw the landmass in the Mercator projection. Find the most NW point,
e.g., by scaning a NE-SW line across the map. That's it! The Mercator
projection is the one to use because it's the only one ...
- 3,176
4
votes
Accepted
Why are my icosahedron triangle subdivisions not equilateral (PostGIS)?
Yes, this is due to the tiled icosahedron to-sphere projections. I think of this process as:
Take a normal icosahedron, all corners lie on the same sphere, and therefore, the distance is also the same,...
- 1,091
3
votes
Accepted
Complexify geography polygons in PostGIS
I think you can use ST_Segmentize to do this (especially if you have Geography objects).
Returns a modified geometry having no segment longer than the given max_segment_length. Distance computation ...
- 79k
3
votes
Accepted
ArcPy Insert cursor losing vertices when writing Polygon features?
Try adding sr to arcpy.Polygon(polygon, sr)Here is the reason why:
I sometimes see significant coordinate movement when I do not supply a Spatial Reference to an Arcpy Geometry object such as a ...
- 7,447
3
votes
Accepted
Would nearest point using Geodesic distance and nearest point using Haversine distance be the same point?
For sure, "closest" will return different points, in general, for
great-circle (what you call haversine) and geodesic distances. For a
specific example, consider the set of points {A, B} where the ...
- 3,176
3
votes
Accepted
What's wrong with using latitude and longitude as X and Y on a Cartesian space?
Everything really. Distances will become meaningless. Areas will become meaningless. Hence all outputs such as slope will become problematic. As you move in latitude then your "grids" will appear to ...
3
votes
Figure out location of city direction sign in image - friday fun project
I am the author of this picture. So I can tell for sure the sign post is located in Thessaloniki, Greece.
- 31
3
votes
Why is SQL Server 2019's STDistance Very Slightly Different Than The Vincenty Formula? (Same Up To ~0.0001km)
Without having access to the source code of SQL Server it may be impossible to say. As a comparison, PostGIS ST_Distance query from the geography example of https://postgis.net/docs/ST_Distance.html ...
- 60.1k
3
votes
Accepted
How is it possible to calculate azimuth from a single lat lon cordinate with x, y offsets in meters?
After couple of days of searching and testing I finally managed to get this to work.
The first question was whether it was possible to calculate azimuth using an image's x,y pixel coordinate.
The ...
- 151
2
votes
Buffer not providing accurate geodesic buffers in ArcGIS Desktop 10.0?
I just tested this in ArcMap 10.3 and it has produced accurate buffers based on the field 'Dist' in my point feature class: arcpy.Buffer_analysis(in_features="//pmgfile01/Users/jb/Documents/ArcGIS/...
- 6,900
2
votes
Moving dead ahead: rhumb line, great circle or none
I know the question has answered already, but allow me to show you something cool for future use:
A live Google map where you can move the edge markers affecting the great circle and rhumb line same ...
- 21
2
votes
JTS Vividsolutions API: compute First (direct) geodetic problem
I would much rather suggest doing it manually since the math is simple. This will be much faster than using so many potentially complex methods.
public static Point createPointInDistanceAtAngle(Point ...
- 10.3k
2
votes
What's the name of the area between two geographic coordinates?
A quadrangle?
Yes, it is named: spheroidal quadrangle.
- 13.2k
2
votes
Get Radius in epsg 4326 with Openlayers 3
Found it..
var formatRadius = function(Circle) {
var radius;
if (geodesicCheckbox.checked) {
var center = Circle.getCenter();
var pointOnPerimeter = [center[...
- 567
2
votes
Accepted
When calcuating distance between points on Earth why are my Haversine vs. Geodesic calculations wildy diverging?
I appreciate your code because it contributes to geodesy, by allowing to make some interesting analyzes in a practical way, regarding spherical approximations for the calculation of length of geodesic ...
- 13.2k
2
votes
When calcuating distance between points on Earth why are my Haversine vs. Geodesic calculations wildy diverging?
There was a matrix algebra error in the Haversine formula. I updated the code in the question. I am getting much better agreement between Haversine and geodesic now:
On my actual dataset:
- 193
2
votes
Creating a geodetic line that goes around the whole ellipsoid with pyproj
pyproj hooks up with the geodesic routines (I am the author of
these) in proj.
The geod_directline and geod_inverseline functions both initialize
objects which allow you to compute points on a ...
- 3,176
2
votes
Accepted
Figure out location of city direction sign in image - friday fun project
Just eyeballing this on a globe view with a measure tool like: https://map.terria.io/
Makes me think the location is in Southern Greece.
Using an online app like https://www.distancefromto.net we can ...
- 13k
2
votes
Figure out location of city direction sign in image - friday fun project
If you want to measure (real world)- distance, don't draw circles / create buffers on a flat map canvas. Using EPSG:3857 / Web Mercator is especially a bad choice for measuring distances or areas, as ...
- 60.2k
2
votes
Choosing projection for running polygon intersections at global scale (i.e, geodesic intersections)?
You should not use a projection (except for making maps; or when you must use an algorithm that really cannot deal with angular data). For area computations in R, you should use the lon/lat data. That ...
- 9,971
2
votes
Is order among distances preserved when using Geodesic and Cartesian distances?
No! And it's pretty easy to find counterexamples (where the cartesian distances
are ranked opposite to the geodesic distances). For example, for the
WGS84 ellipsoid, pick 3 points with positions
...
- 3,176
1
vote
Accepted
What's the name of the area between two geographic coordinates?
More informally than a spherioidal quadrangle, a much more common and useful term is "bounding box", sometimes shortened to "bbox".
- 8,373
1
vote
What's wrong with using latitude and longitude as X and Y on a Cartesian space?
Latitude and longitude are not linear measures, and a planar calculation of distance using them will yield nonsense results. Although lines of latitude, or parallels, are evenly spaced, and could be ...
- 3,852
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