# Tagged Questions

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

169 views

### Compute visibility graph on sphere

I have a PostGIS table with some polygons (stored using the geography data type). They represent regions on a spherical earth. For each pair of vertices chosen from among all the polygons, I want to ...
134 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 ...
133 views

### Calculating a point Lat/Lon from another Lat/Lon point angle

I need help for a solution of this problem to make an algorithm: : I have a point O center of a circle of radius r, on this circle there is two point P1 and P2. I know latitude and longitude of ...
28 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 ...
235 views

### Rhumb lines intersection

I looking for algorithm how to find out whether two rhumb lines given by point1 with azimuth1 and point2 with azimuth2 have intersecting point. Have anyone idea how to find intersection ? For example:...
39 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 ...
1k views

### Bearing/Course/Heading in WGS84 ellipsoid model

There is a common formula for computing the initial bearing for a course from lat1, lon1 to lat2, lon2. (And yes, I'm aware that the course will change when traveling). atan2( sin(lon2-lon1) * cos(...
31 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 ...
235 views

### Determine PostGIS geography polygon orientation

How can you determine the orientation of a PostGIS geography polygon? I'm looking/hoping for a function that would tell me which side is the interior (left or right) as you traverse the vertices of ...
95 views

### How can I figure out whether a sphere is intersecting the Earth between a given lon/lat range?

Given a lon/lat range that represents a tile on the Earth's surface, I need a computationally efficient way to figure out if a spherical volume defined by a point (assume ECEF coordinates) and a ...
119 views

### Find arc endpoint with bearing and radius counting with curvature of the earth?

So my problem is that I have start point [lat,long] for arch, bearing, radius and I need compute end point [lat,long] ? End point should be in 180 degrees angle from start point and I should be aware ...
237 views

### Centroid of the equator and a point

Suppose I already have a way to compute the centroids of different geometry types: Points (arithmetic mean of Cartesian coordinates). Linestrings (polylines) (weighted mean of segment mid-points in ...
194 views

### Placement of a fixed-radius circle on a sphere to maximize point containment

There are many papers on the "Circle Placement Problem" in 2D Euclidean space, but I haven't been able to find any papers discussing this problem on the sphere. The problem is: given a set of points ...
55 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 ...
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-...
94 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 ...
118 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 ...
370 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 ...
201 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 ...
837 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 ...
404 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 ...
15 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/...
45 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 ...