# Questions tagged [spherical-geometry]

Spherical geometry is the geometry of the two-dimensional surface of a sphere.

155 questions
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### Problem with gdal_translate when converting a GeoTiff with spherical datum to a netCDF

I have a raster file with LCC projection and spherical datum. It actually has the following proj4 parameters: +proj=lcc +lat_1=45 +lat_2=22 +lat_0=38.7 +lon_0=20 +x_0=0 +y_0=0 +a=6370000 +b=6370000 +...
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### Area between two longitudes? [closed]

I am trying to compute the area between two longitudes (using the angle between them) but am having a hard time. I can do that more easily between latitudes but longitude reveals to be tricky. Anyone ...
78 views

### Checking small distance calculation in UTM zone 31 ETRS89

I'm afraid I've a very basic question about interpreting UTM grid values: Are the grid references in metres? I have data from the Spanish catastral map labelled as UTM Zone 31 ETRS89, and want to ...
28 views

### How to calculate area of 1 x 1 degree cells every one degree?

I've calculated mean data values of each 1 x 1 bin like this: import numpy as np from scipy import stats north=50.5 south=21.5 west=-110.5 east=-76.5 bin_lon = np.arange(west, east, 1) bin_lat = np....
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### Find coordinates of extended line segment intersects with given longitude

I have a line between C1 and C2; My Coordinates are; C1: 36.454N - 21.785E C2: 41.725N - 38.475E I want to find C3 latitude value based on given longitude when I extend my C1-C2 line segment. IE ...
153 views

### Oblate ellipsoids and latitude

I've been reading Wikipedia and am having a bit of trouble. https://en.wikipedia.org/wiki/Latitude Geodetic latitude would clearly change if the Earth were squashed vertically. But would places ...
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### Latitude of Earth reference ellipsoid [closed]

I am trying to create a graphic demonstrating the difference between an idealized perfect sphere and the Earth's reference ellipsoid. (I know this is also an approximation, but nevertheless.) To this ...
1k views

### Creating buffer circle x kilometers from point using Python?

I am wanting to create a circle with an inputted radius around a point of predetermined latitude and longitude. I've been trying to use the formula found in this post which uses an algorithm ...
172 views

### How to generate a Global Voronoi diagram?

Using arcMap, QGIS and similar software it is easy to create a non-global Voronoi diagram. The resulting shapefile polygons however are showing weird behavior when crossing the -180 meridian or the ...
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### How to calculate intersection of two arcs? [closed]

Given two arcs (defined by start and end points with latitude and longitude) how to check if there is intersection (cross point) and if there is -- how to calculate it? Calculate "manually" -- i.e. I ...
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### Distance of a Lat long from a Polyline

I am currently looking for a solution where i need to find if a lat long is on the route or not. I cannot use Google Maps Geometry IsLocationOnEdge() or ContainsLocation() api's as i am working on a ...
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### Calculate vx, vy and vz components from Lat,Lon, height and Time

Referring to the following post Calculate velocity x and y components from Lat,Lon and Time Given the two points with Latitude, Longitude, Height and time P0 = (Lat0,Lon0, h0, time0) and P1 = (...
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### Using Spherical Standard Deviation to identify ledges on steep cliffs? [closed]

I have been implementing the approach highlighted here: Finding regions or zones in raster DEM of similar slope or aspect values in ArcGIS for Desktop? to calculate firstly the "spherical variance" ...
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### plotting a circle in a spreadsheet

I can't get my head around plotting a circle on a big sphere (Planet Earth). I have a column that has 180 rows - 1 for each degree. The next row is each degree converted to radians. Easy so far. A1 ...
254 views

### Map camera image onto sphere

How would I determine what the red point (phi', theta') is for a camera oriented at a known (phi, theta) is from a given image? The point of this is to determine what (dphi, dtheta) is so that I can ...
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### Converting spherical coordinates to geographic coordinates in complicated netcdf file [closed]

I am very new with netcdf file. And currently have to extract the data from such netcdf which looks like below: 8 variables (excluding dimension variables): double time_bnds[bnds,time] ...
120 views

### Find lat/long of Point 2 a given distance from Point 1

I'm creating a program using the Bing Maps API where the user inputs a bounding box with lat/long, and the program extracts a number of static images at zoom level 15 to later be mosaicked together. ...
123 views

### How can I build CRS string in Trasverse Mercator to increase distance measurement accuracy?

I've searched a lot in the forum finding several answers to part of my problem. In brief I need to make some computation keeping in account the distance from every point along different angles until a ...
543 views

### Whats the unit of circle's radius in Google Maps

I need to know what is the unit of radius (e.g. miles, kilometers etc) in following question: How to place markers on the outline of a circle in google maps?
330 views

### Calculate velocity x and y components from Lat,Lon and Time

I'm trying to calculate velocity components in the X and Y direction given two points: P0 = (Lat0,Lon0,Time0) and P1 = (Lat1,Lon1,Time1) The points are pretty close together so the components ...
766 views

### Understanding the s2 library (geometry on the sphere, cells and Hilbert curve) for finding points nearby

I am having trouble understanding how the S2 library works so things in this question may make no sense, but I have a goal I would like to accomplish. Lets say I have many lat/lng point I want to ...
117 views

### Azimuth, elevation and distance for point-to-point radio links [closed]

After plotting our point-to-point radio sites and links in QGIS using Ordnance Survey map layers I'm wondering whether I can extract some information for this. For each link I would like to ...
72 views

### Why computing the distance between two ellipsoidal coordinates needs to be iterative?

I have found internal Android code that calculates distance between two spheroidal coordinates. It is complex and it is iterative. Why? Can't this calculation be done in "single shot"? The Java code ...
313 views

### How to calculate the great circle distance along a curved surface?

I know we can calculate great circle distance on a sphere by haversine formula. But what if on a curved surface, as the topography of our real Earth? How do we calculate the surface distance?
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### Plotting a hyperbola, or, solving spherical triangles

I am trying to create a GeoJSON path containing lines of hyperbola, in order to recreate Decca Navigator charts in QGIS, something like this: The chart has nine lines of hyperbola plotted between ...
1k views

### How to calculate straight line distance from spherical distance

I have longtitude and lattitude coordinates of one point and spherical distance between this and another point on Earth in kilometers (the shortest distance over the earth’s surface). I need to ...
126 views

### Postgis St_Project calculation method

I`m trying to implement postgis St_Project analog on C++ (calculation method is taken from here - http://www.movable-type.co.uk/scripts/latlong.html): #include <cmath> struct GeoPoint { ...
849 views

### How can I compute global triangulation from longitude/latitude coordinates?

I want to calculate an approximate location based on these inputs: 3 locations identified by latitude and longitude anywhere on a planet 3 angles, indicating the approximate direction from each of ...
516 views

### PostGis: Calculating distance in different methods, What's the difference?

What is the most efficient (or just "best practice") way to calculate distance between 2 points, assuming we are on 2D world without big circle etc. phenomenon (distances up to 300 meters). Method 1: ...
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### walk me through tdoa [closed]

I'm working on a TDOA application. This is just something in my free time to see if my hardware can accurately do it and it sounded like a cool challenge. Regardless if it looks possible or not, I'm ...
318 views

### Getting H2GIS functions to work in Spherical Space?

I've been playing around with H2GIS (http://www.h2gis.org/) for a project at work and am struggling to get the H2 functions to operate in spherical space (lat/ lon), rather than cartesian space. The ...
172 views

### Calculating distances (differences?) between two regions?

I am building a machine learning system which predicts the location of tweets as a bounding box (using the google maps API among other things). Since the twitter API also supplies a bounding box, I am ...
253 views

### How to properly deal with rectangles being curved on geographies?

I'm using Microsoft SQL Server to store simple data for administrative boundaries of the world (lots of polygons). I store this in a geography data type column. Afterwards I query these polygons by a ...
230 views

### PostGIS - st_intersects using polygons that cross antimeridan/equator

New to using PostGIS and have two situations that I'm working with. In the one case, I have a polygon that crossed the antemeridian and was detecting whether a two separate points located within that ...
918 views

### How big does a circular geofence need to be for the curvature of the earth to matter? [duplicate]

I'm working on adding geofences to a mobile application. I know the proper way of calculating distance between two points on a sphere is using the great-circle or Haversine formula. I don't know if ...
360 views

### JTS polygon intersection calc on a geoid

I am using JTS to compute intersections between polygons with WGS84 lat/lon coordinates. I am not converting coordinates to anything 2D based, just reading in POLYGON(lat lon, lat lon) and doing ...
273 views

### Transforming zonal and meridional velocity from regular lat lon to rotated lat lon?

Like in Transforming regular lat/lon to rotated lat/lon? that was asked before, I am working with climate data and I need to transform zonal and meridional velocities (u and v) from regular lat lon ...
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### How to make a point from real latitude and longitude values

My program has a center point and one moving object . At this moment this point is somewhere in Europe.But Now i have to change that point from the latitude and longitude values(of Australia) . Please ...
183 views

### Getting coordinates at location n meters from known point to NW and SE using ArcPy?

I have a point shapefile or feature class and I want to create bounding boxes around each point. The size of the bounding box will depend on user input, for example the user might want a bounding box ...
244 views

### After how much distance does the x,y coordinate system become noticeably distorted?

I'm working with maritime sensors that give information of moving objects it detects, in azimuth, range and elevation, and we convert it to x,y coordinates for our application to be able to process it....
2k views

### Polygon area calculation in Ruby (on Rails, rgeo, PostGIS and GEOS) in sqare meters

In a Ruby-on-Rails application, I need the area in square meters (or any other surface measure, be it ares, hectares, square kilometers, but not in pseudo surface measure like square degrees) of a ...
341 views

### XYZ bounding box of a spherical polygon

I'm looking for an algorithm to calculate the 3d bounding box of a spherical polygon - i.e. the min/max X, Y and Z over that part of the surface of a unit sphere. The purpose is to aid fast area-...
556 views

### Algorithm to draw a perpendicular line on Google earth (KML)

I have two points say A (lat,lon ) and B(lat,lon) and I want to draw a perpendicular bisector line to AB such that any point (C) on the perpendicular line satisfies AC=BC. All I want is a function ...
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### Is there any online viewer which displays the polygons assuming great circle lines for the edges?

My question is similar to this one: Are there any online WKT editors? The links given in answers have been very useful to me. However, it seems that when the tools in question display maps, they ...
2k views

### Project location on a (great circle) path

I've been searching this SE site for quite a few hours now, and I'm still struggling to find a solution to my question. My goal is that given a way in OSM and my location (lat/lon coordinates), I want ...
298k views

### Calculating longitude length in miles?

Suppose I have geographic coordinates of "Saratoga, California, USA" as Latitude: 37°15.8298′ N Longitude: 122° 1.3806′ W I know from here that in case of latitude 1° ≈ 69 miles and that ...
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### Proof of part of haversine formula?

I'm trying to study how to find the distance between two points if their latitudes and longitudes are given. I have a question about the proof of part of the haversine formula given at Math Forum. ...
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### Given distance (in meters) what is the angle in geographic reference systems? [duplicate]

In QGIS and other systems sometimes I have a layer in geographic reference system (typically WGS84, EPSG:4326) and I'd like to calculate a buffer of say 5000m around a point. So, given a point ...