# Tagged Questions

A geodesic is the shortest path between two points on a curved surface; in this context applies to questions where the curved surface is the earth's surface.

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### Using Geodesic Measurements for Circle Radii?

I am currently developing an OpenLayers mapping site. Measurements can be made using a line tool, and an area tool. Both of these are currently set to calculate geodesic measurements as outlined in ...
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### Are long lines in shapefiles to be considered geodesics or straight lines in the 2D latlong space?

Is there a definition on how lines connect vertices in the shapefile format? In the simplest case, imagine a line with only 2 points, from 40,-118 to 40,-112 - that's somewhere random in the US - ...
857 views

### What kinds of line segments/edges require high accuracy in a true surface-of-the-ellipsoid representation?

I've been musing (and doing prototype coding) for a 'projection free' geographic codebase with your basic point, line & polygon primitives. Rather than dealing with all the sacrifices that come ...
835 views

### How to generate geodesic linestring from two points in C#

I'm looking for a FREE C# class, library or set of functions that will allow me to generate a geodesic linestring (or array of vertices, whatever) from two decimal degree points. I've found ...
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### How to compute geodesic area in GeoDjango?

I have some polygons which can be anywhere in the world. I would like to compute their areas. The GeoDjango docs for GEOSGeometry.area don't specify whether it is geometric or geodesic area, but ...
313 views

### Modifying straight line segments so they follow geodesic / great circle paths using QGIS

I have a kml file showing a dodecahedron stretched across the surfce of a globe, which I downloaded here: http://montalk.net/cgi-bin/coordinates.py I would like to re-project this dodecahedron so I ...
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I think I understand the whole rhumb line and great circle idea but I can't seem to find an answer on this question. Suppose I am driving a car (i don't use ship because I don't want to put the ...
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### Direct Geodesic with Point 2 Azimuth

I am trying to find a way to calculate the direct problem on the WGS-84 ellipsoid but instead of using the initial Azimuth (e.g. lat1, lon1, distance, fwd azi), I want to compute it with the reverse ...
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### Which one of these azimuth values is the right one? And why?

First of all, let's make clear that I want the Azimuth on the surface of the Earth, i.e. the angle between two locations, for example New York and Moscow. I am testing some azimuth calculations with ...
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### Alternatives to the Vincenty geodesic functions in OpenLayers 3?

I'm migrating an application from OpenLayers 2 which uses OpenLayers.Util.destinationVincenty() to compute the projected latitude and longitude of a point from an origin given an angle and distance in ...
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### Geodesic measurements for short distances throughout US?

My ArcGIS experience has been limited to working on large-scale maps with planar projections. I'm moving to a project in which I want to calculate the distance between pro sports facilities throughout ...
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### ArcPy Insert cursor losing vertices when writing Polygon features?

I'm currently trying to code a geodesic buffer from points (the one that is implemented in ArcGIS is very slow). The idea is to calculate 100 point coordinates (P_Buffer) around an initial point (P) ...
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### Prior art on rhumb line and great ellipse areas?

I'm adding the computation of the area betweeen a rhumb line or a great ellipse and the equator to GeographicLib. My formulations are briefly given in here and here. These formulations are similar ...
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### Hive GIS ST_GeodesicLengthWGS84 not returning expected distance

I am trying to find the distance between two points (in meters and not degrees) using GIS Tools for Hadoop by ESRI. The ST_Length provides distance in degrees and hence I used the ...
173 views

### Air corridor in spherical surface: calculating great circle tangent points with small circles

I have the necessity to draw on a sphere (earth) an air corridor. In the cartesian plane, this corridor is made by some circles and from outer tangents that connect these circles as you can see in ...
460 views

### calculating bounding box from known centre coordinate and zoom

I have a map, the centre of that map (centrepoint) is = -37,175 ( gps) I know the zoom of the map = 13 I know the size = 320x320px I know there is 111111m in a degree of latitude and a varying degree ...
472 views

### Creating a Geodesic Polyline Buffer in OpenLayers

I have a feeling that the answer is going to be 'You can't do that without some very complex coding' but I thought I'd go for it anyway. I recently asked a question on how to create a Polyline Buffer ...
495 views

### How to validate OpenLayers area calculation using PostGIS?

I am working on a GIS API that work on top of OpenLayers. I have a feature that calculates the area of a drawn polygon. I have tested it on the browser and the areas I got, appear to be correct. For ...
1k views

### How to draw a circle in OpenLayers 2 and measure its radius dynamically?

With OpenLayers 2.13, I want to draw a circle and obtain its radius at each mousemove. The radius would then be returned as arguments of a callback function, for example. But of course, this is not ...
343 views

### testing if a Geodesic polygon contains a point c++

I am looking for an algorithm, preferrably in C++, that can take a point (lon,lat) and determine whether that point is inside a geodesic polygon. Is there such an algorithm freely available?
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### Is the Azimuth on the equator equal to the one not on the equator?

I am trying to fully understand the concept of Azimuth and I am encountering some inconsistencies (or maybe it is my error). I show you some examples that do not match, hoping somebody can explain me ...
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### Measuring Geodesic Distance in ArcGIS for Desktop? [closed]

I'm working with only a basic/student license for ArcGIS 10.1 on an ocean mapping project. I've created a grid that covers all ocean area, capturing various characteristics within that grid (the ...
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### Calculate geographic position based on azimuth, distance and height [duplicate]

How to calculate the geographic position of an object in sky (Point B)(like an aircraft) from Home Point (Point A) based on only four variables: Lattitude and Longitude at Home Point, Azimuth at ...
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### JTS Vividsolutions API: compute First (direct) geodetic problem

I'm using the popular JTS Vividsolutions API for Java. I'm struggling to find if I can perform calculation of the First (direct) geodetic problem with the API. Is there a way to calculate this with ...
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### What's wrong in using latitude and longitude as X and Y on a Cartesian space?

What can go wrong and what kind of error can build up if I use geodetic coordinates as if they were cartesian and place my objects into my world with no conversion formulas?