# Tagged Questions

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

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### How do I convert OS coordinates (X and Y) to longitude and latitude coordinates?

How do I convert OS coordinates (X and Y) - Eastings and Northings to longitude and latitude coordinates? For example X and Y below X (Eastings): 347904 Y (Northings): 287484
658 views

### Given a flight path given in latitudes and longitudes, how do I find another flight path that is parallel to the path given?

Given a flight route that is given in latitudes and longitudes, how do I find another route that is "parallel" to the route given (find a perpendicular line to each waypoint given)? I think the best ...
308 views

### How to calculate smallcircle on sphere

I use this python code to calculate a greatcircle: https://code.google.com/p/pyroms/source/browse/trunk/pyroms/greatcircle.py?r=39 After initializing the greatcircle I can calculate points on the line....
19 views

### 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 ...
56 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 ...
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### 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 ...
150 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 ...
89 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-...
34 views

### Calculate an intersection point of multiple spheres on the surface of earth [duplicate]

The question i am going to ask is very much similar to this question-How to calculate the intersection of 2 Circles? But the problem here is, the radius of the spheres are too small (within 8 meter). ...
95 views

### How to Increase the length of column type geometry in postgres(pgAdminIII)

I am just wondering is there any way to increase the default length of column type geometry in postgres. Since we are trying to save large number of vertices polygon in to the geometry column geom in ...
119 views

### Mapping from one plane on the other plane despite of masking regions

have a set of data given here, where in the first and second columns there are the sky coordinates (ra,dec) e.g. right ascension and declination, respectively and in the third and forth, the ...
36 views

### Pont to Point and Point to Line Calculations [duplicate]

We have been beeating our head against a wall trying to get point to point and point to line segment (perpindicular) to work in PHP. I posted the other day as well but did not include the code in ...
27 views

### Find coordinate of point on the boundary of a circle given a latitude/longitude and radius [duplicate]

I understand how to use the haversine formula to compute the distance between two points on the earth. However, I would like to answer a similar, albeit different question. How can I compute the ...
372 views

### Intersection between a ray from lat, lon, alt, with pan, tilt and earth's surface

I have a problem that consists of finding the intersection point between a ray from a given lat, lon, alt, that is looking to a given pan and tilt angles and the earth's surface. I need the lat, lon ...
202 views

### recalculate latitude and longitude from a pixel in a cropped map

i want to recalculate a geographic coordinate from a pixel in a map. For this i have the size and the coordinates from the map to convert a coordinate to a pixel is use the algorithm, you find at ...
843 views

### How to approximate point to segment distance on sphere?

I would like to approximate the distance of a line segment from a reference point on the map (coordinates are gives as lat/lon). In the Cartesian coordinate system I would simply find the closest ...
618 views

### How to get screen coordinate from geographic one?

I need to know, how can I convert some geographic coordinates to the screen one. I want to remind you about desktop coordinates system, how it look like: I've developed soft, which is loading map ...
405 views

### Locating the centroid (center of mass) of spherical polygons

I'm trying to work out how best to locate the centroid of an arbitrary shape draped over a unit sphere, with the input being ordered (clockwise or anti-cw) vertices for the shape boundary. The density ...
18 views

### Finding the exact coordinates of circle's extreme east and west points on a sphere [duplicate]

I'm currently implementing the Bentley-Ottman algorithm applied to spheres, involving intersections of many spheres on one sphere, circles in most cases of course. This requires locating "event" ...
257 views

### Spherical Mercator to Cylinder mercator?

Hello I want to create an overlay for google maps. As far as I know google maps using Spherical Mercator, so the system where I read the maps use Mercator but is not specified which (spherical or ...
773 views

### 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 ...
47 views

### Hard to get my head around, generating average price for houses in each quadrant

I'm able to determine the average price of houses sold in a particular area (like the squares on image below) dependent upon postcode. Although I can generate the average sale price for a particular ...
983 views

### Specifying a rectangle as two latitude/longitude pairs, one for center and one for size

I am trying to make sense of the Google S2 library for spherical math (it works like this). I need to get a rectangle for searching for nearby entities in a database, based on a point and a distance (...
30 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 ...
19 views

### Requesting Mongodb collection with 2dsphere index from Leaflet LatLng

I am using projection and 2dsphere index. Similar posts have been done on mongodb support site but it may be a pure GIS problem,so here I am ^^. My scenario is the following : I create a Point/...
46 views

### How to find angle between 3 points on sphere? (in javascript)

How to calculate angle between 3 points on sphere? Currently i've got function correct for cartesian space: function find_angle(A,B,C) { var AB = Math.sqrt(Math.pow(B.lon-A.lon,2)+ Math.pow(B....
53 views

### Triangulation of Cell Towers using MSQL Server Spatial

I need to triangulate a GSM Device by using known cell towers locations and GSM readings. All Data is in a MS SQL Server as Geometry Types. herewith an example of the data : here is also a SQL ...
28 views

### Determining North-South Line Via Watch Method?

I read about Determining North-South Line Via Watch Method recently (page 9). What is the underlying geometric/celestial reason this works? What is the error to true north given this method? Is ...
52 views

### 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 ...
27 views

### Find square with latitude and longitude for given lat and lng and distance [duplicate]

I have the coordinates of some point, lets say lat and lng, I want to find the latitude and longitude of top left and bottom right corners of the square, whose sides are located k kilometers from the ...
28 views

### Quickest method for determining which postcode is 2 miles north of original postcode? [duplicate]

What is the Quickest method for determining which postcode is 2 miles north of original postcode? For instant L17. I know how to determine the distance between 2 points as below, but the above ...
812 views

### Implementing custom (Vincenty/Haversine formula) functions for MySQL vs Using PostGIS?

I currently am using MySQL for all of my relational data. I have hit a crossroads with geo calculations. Since, MySQL does not have good support for spatial functions, I am contemplating on using ...