Activity for AGP
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AGP posted a comment on discussion Help
Completely understand. I took the specific problem of a range circle and tried to generalize it to a range ellipse. I tried to incorporate geodesics to come up with a suitable definition. For my purposes I am trying to minimize the points used in a path finding algorithm. The flatness of the ellipse will determine how "far out" we will search for connection points. Many thanks for your help.
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Here are a couple of samples: MIA to ORD BNA to CUN LAX to YYZ
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Here are a couple of samples: MIA to ORD BNA to CUN LAX to YYZ
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Here are a couple of samples: MIA to ORD BNA to CUN LAX to YYZ
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Here are a couple of samples: MIA to ORD BNA to CUN LAX to YYZ
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Here is where I am with this challenge. I assume all my coordinates are in WGS84 and the input is ptStart and ptEnd. The I proceed as follows in .NET using the wrapper classes: 'assume a WGS84 datum Dim geod As Geodesic = New Geodesic 'WGS84 Dim s12 As Double, azi1 As Double, azi2 As Double Dim a12 As Double = geod.Inverse(ptStart.Y, ptStart.X, ptEnd.Y, ptEnd.X, s12, azi1, azi2) Dim geoLine As GeodesicLine = New GeodesicLine(geod, ptStart.Y, ptStart.X, azi1, Mask.ALL) 'calculate geodesic distance...
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OK let me give this some thought and i will see what I can do with it.
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Based on the discussion on range rings from this post https://sourceforge.net/p/geographiclib/discussion/1026621/thread/1df0a86b/ I have been able to recreate geodesic circles that are dead-on when compared to ArcGIS. What I am researching now is how to extend that to "range ellipses". A description here http://desktop.arcgis.com/en/arcmap/10.3/tools/data-management-toolbox/table-to-ellipse.htm. If we take this geodetic ellipse on the surface of the earth and generalize it to have a constant radius...
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Ok so got something working. I have a GeoLine0 which is known. I then need to create another GeoLine1 that intersects with GeoLine0. At the intersection pointA I know only the azimuthA. I also know the coordinates of PointB. So I guess by creating a tempLine from PointB using azimuthB ~ azimuthA - 180. I use 25NM distance for the temp line since that will gurantee that it intersects GeoLine0. That is my first guess so now I go back and calculate azimuth@guess. if it is within 0.001 degrees to my...
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That's definitely not small for my purposes. But its a good starting point. I'll post once I have something working.
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Ahh thank you for the explanation. I had theorized since my lines were small (~25NM) that the azimuths would be close. Actually I think I can use this initial guess to start an iteration to get to my solution. Many thanks.
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Was looking at the examples for Direct and Inverse geodetic calculations and I think i have my head wrapped around most of them. I currently am creating a geodesic line from Point A to Point B using a WGS84 datum. Question: is the initial azimuth from Point A to Point B the same as the initial azimuth from Point B to Point A but with a -180 degrees offset? My gut tells me no but I'll do some testing.
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Thanks for the info. I have maybe 2 or 3 of these intersections to do in one process so I dont think it will affect me much. I was just pondering about the difference in approaches. Many thanks. I have another similar question but will post in its own thread.
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I already have two very densified geodesic lines that I drawn on my map. The map is displaying data in WGS84. The lines have a starting point, an initial azimuth, and are length 25NM. I chose 25NM since I am fairly sure that these lines will intersect once within that range. I can clearly see where they intersect so what I am doing is using an ArcGIS function to determine that intersection point. This works only because my lines are geodesic densified. So my thought was that compared to your idea...
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Doing a little research and came across this post https://sourceforge.net/p/geographiclib/discussion/1026621/thread/21aaff9f/. My problem is similar but wanted to get your opinion. I have two segments: the first is defined as a starting point and an azimuth, and the second is two points. I work with the WGS84 datum. I need to find where the two lines intersect. My work area is fairly small so I know that my segments will probably be within a 25NM radius. So what I am doing now is extending each line...
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OK so re-reading some of the documentation I see that GeoLib uses an algorithm that resolves some of the issues with Vincenty. I also agree that ArcObjects most probably uses Vincenty with different tolerances. I think GeoLib from the start was going to be the replacement library of my choice but had to convince myself that it was accurate. I also needed a study that would show disparities with other libraries and an explanation of why they existed. I am fully convinced that GeoLib gives the correct...
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Ok so I ran the study with my start point and the distance and azimuth given by GeoLib. The results show that on direct problem they all are fairly accurate with GeoLib being accurate to the 13th decimal of end coordinates. Do the direct and inverse problems use different algorithms but based on the same premise? I just don’t get why the disparity in distance is so large. Gavaghan------------------------------- Expected Delta Start Point Longitude -161.447217064652000 degrees Start Point Latitude...
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Doing some research to replace the functions I use in ArcObjects. I ran some minor tests and GeoLib showed that it was a great replacement. To fully convince myself I then ran about a half-million cases with a random start point and a random end point. All looks good but this one case stuck out. The first case is to show that I am running the process correctly. The second case is the one that looks dubious. Granted it is a path that goes half way around the world so maybe that’s the issue. I am using...
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Doing some research to replace the functions I use in ArcObjects. I ran some minor tests and GeoLib showed that it was a great replacement. To fully convince myself I then ran about a half-million cases with a random start point and a random end point. All looks good but this one case stuck out. The first case is to show that I am running the process correctly. The second case is the one that looks dubious. Granted it is a path that goes half way around the world so maybe that’s the issue. I am using...
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rrently what I do is estimate the perimeter by C = 2piR. So with a radius in meters I can get the perimeter length in meters. Once I have that then I divide by the MaxArcLength to get number of slices I need. So then I just do a For az = 0 To 360 Step N and generate an outer point. Connecting the outer points gives me the vertices of my polygon (range ring). Let me try your approach to see how that affects the process. In this case, this step only provides the number of slices I need to make to get...
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rrently what I do is estimate the perimeter by C = 2piR. So with a radius in meters I can get the perimeter length in meters. Once I have that then I divide by the MaxArcLength to get number of slices I need. So then I just do a For az = 0 To 360 Step N and generate an outer point. Connecting the outer points gives me the vertices of my polygon (range ring). Let me try your approach to see how that affects the process. In this case, this step only provides the number of slices I need to make to get...
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rrently what I do is estimate the perimeter by C = 2piR. So with a radius in meters I can get the perimeter length in meters. Once I have that then I divide by the MaxArcLength to get number of slices I need. So then I just do a For az = 0 To 360 Step N and generate an outer point. Connecting the outer points gives me the vertices of my polygon (range ring). Let me try your approach to see how that affects the process. In this case, this step only provides the number of slices I need to make to get...
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rrently what I do is estimate the perimeter by C = 2piR. So with a radius in meters I can get the perimeter length in meters. Once I have that then I divide by the MaxArcLength to get number of slices I need. So then I just do a For az = 0 To 360 Step N and generate an outer point. Connecting the outer points gives me the vertices of my polygon (range ring). Let me try your approach to see how that affects the process. In this case, this step only provides the number of slices I need to make to get...
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rrently what I do is estimate the perimeter by C = 2piR. So with a radius in meters I can get the perimeter length in meters. Once I have that then I divide by the MaxArcLength to get number of slices I need. So then I just do a For az = 0 To 360 Step N and generate an outer point. Connecting the outer points gives me the vertices of my polygon (range ring). Let me try your approach to see how that affects the process. In this case, this step only provides the number of slices I need to make to get...
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I have gone through and added the library to my .NET project and it is magnificent!!! It has all the functions that I desperately needed. Thank you so much. One thing I am looking to do is to create range rings. In other words from an origin point how far would an aircraft be able to travel as a radius. The outer perimeter would construct a geoellispe. Would I just cycle through a number of azimuths and use the origin point, the azimuth, and the distance to get each and every point on the perimeter?...
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Tested with a small, medium, and large DPI on Windows with the same results. Namely...
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Tested with a small, medium, and large DPI on Windows with the same results. Namely...
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OK tested at home with a 14,000 line text file. The Nav Bar does show as intended....
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Tested with a small, medium, and large DPI on Windows with the same results. Namely...
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I will try at home with Win8.1 x64. I will also try to test various DPI settings...
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Also the shortcuts for the navigation Previous, Next, First, Last don't seem to work....
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Same problem here. NotePadd++ v6.5.4 with Compare plugin 1.5.6 on a Win 7 x32 machine...
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