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Feb
3
comment Checking if two WGS84 lines intersect in JavaScript
The gnomonic projection isn't part of the Javascript library (sorry). However the C++ code implementing the projection is very short. It should be straightforward implementing this in Javascript.
Feb
2
answered Checking if two WGS84 lines intersect in JavaScript
Dec
12
answered About geodesic or azimuth and UTM and Google Mercator projections
Oct
21
comment Semantics of polygon points - How to join the dots?
The Google Earth documentation lies. Polygon edges are not lines of constant bearing (straight lines on a Mercator projection). Instead, they are straight lines in latitude-longitude space (i.e., straight on a plate carree projection). I've pointed out the discrepancy; but no one at Google cares.
Oct
16
awarded  Necromancer
Oct
9
answered calculate bearing from one MapPoint to another MapPoint
Aug
26
comment Geodesic measurements for short distances throughout US?
(1) I believe that Google Maps merely calculates the great circle distance (with a mean earth radius of 6371.009 km) instead of the geodesic distance. (2) It is an often-repeated myth that calculating the geodesic distance is slow. In fact the calculation takes about 2 us with compiled code on a present-day desktop computer -- maybe 5 times longer with "interpreted" code like JavaScript. In many applications, this counts as instantaneous.
Aug
18
comment Why do I get correct area and intersect area when use wrong projection?
GeographicLib-Java obviates the need to project the data to a planar system and it calculates accurately the area of a polygon whose edges are geodesics. It does not deal with intersections of polygons.
Aug
18
comment Why do I get correct area and intersect area when use wrong projection?
The same functionality is available as a Java package, Geographiclib-Java. The documentation includes code to compute the area of a polygon specified as a set of latitude/longitude points with the result given in square meters.
Aug
18
comment Why do I get correct area and intersect area when use wrong projection?
The Planimeter tool gives you the area in square meters.
Aug
18
comment Why do I get correct area and intersect area when use wrong projection?
Probably Albers equal-area is going to provide a decent enough result for your application. However blindly using this projection to calculate the area of Antarctica (which encircles the pole) will give a nonsense result. So for general use, I would recommend calculating the geodesic area so you don't have to worry about the limitations of each particular equal-area projection.
Aug
17
revised Why do I get correct area and intersect area when use wrong projection?
Add bit about edges being short
Aug
17
answered Why do I get correct area and intersect area when use wrong projection?
Aug
17
answered Difference in destination location between pyproj and geopy
Jul
11
awarded  Yearling
May
30
awarded  Necromancer
May
20
revised testing if a Geodesic polygon contains a point c++
Add example code. Perhaps method is exact.
May
20
answered testing if a Geodesic polygon contains a point c++
May
19
answered How to get intersection point from two lines (two coordinated points and two bearings)
May
19
answered Algorithm to draw a perpendicular line on Google earth (KML)