I've noticed that Stellarium uses the center of the sun for entering a constellation but pyephem seems to use the edge and so there are a few hours of difference.
What's the correct calculation (center or edge) ??
If it is stellarium... how to calculate entering the center of the sun in pyephem ??
Thanks
Related
I need to find the formula to calculate the new coordinates starting from the coordinates of a place and adding a certain number of minutes in a direction.
e.g calculate the new coordinates starting from the coordinates of Rome and adding 2 degrees South-East. I found this calculator online:
http://www.geomidpoint.com/destination/
but the distance is in Km or miles, I need to use minutes instead.
Thank you in advance for your precious help!
Monica
I need to Approximate A SyncStart/SyncStop Function in Codesys using PLCOPEN. I don't have access to Part 4 that contains the Synchronized motion stuff. Any ideas on how to start down the right path this in ST would be Awesome.
Like you said there is not a syncstart/syncstop in this version of codesys. If I were you I would
find which axis of motion has the longest distance to travel
find the total time it takes for that axis to travel that distance at its max velocity
find the time it takes for every axis you want to sync
get the ratio of the time for each axis over the time of the longest travel time
multiply that ratio to velocity, accel,decel, and jerk for the corresponding axis.
That will get you pretty darn close.
I need a set of equidistant points (like a raster) each in a 1km distance to the next over a certain area, in my case Germany. I know the feature "regular points" in QGis where I can do just that but the distance you can enter there is not in meters but in coordinates or something. I tried it in WGS 84 as well as in EPSG:31467 (Gauss-Kruger, common in Germany) which is supposed to be in meters but the results seem to be the same..
I just can't find a way to set a certain distance in meters.
Please help :) Thanks!
I have data describing a rotated ellipse (the center of the ellipse in latitude longitude coordinates, the lengths of the major and minor axes in kilometers, and the angle that the ellipse is oriented). I do not know the location of the foci, but assume there is a way to figure them out somehow. I would like to determine if a specific latitude longitude point is within this ellipse. I have found a good way to determine if a point is within an ellipse on a Cartesian grid, but don't know how to deal with latitude longitude points.
Any help would be appreciated.
-Cody O.
The standard way of doing this on a Cartesian plane would be with a ray-casting algorithm. Since you're on a sphere, you will need to use great circle distances to accurately represent the ellipse.
EDIT: The standard ray-casting algorithm will work on your ellipse, but its accuracy depends on a) how small your ellipse is, and b) how close to the equator it is. Keep in mind, you'd have to be aware of special cases like the date line, where it goes from 179 -> 180/-180 -> -179.
Since you already have a way to solve the problem on a cartesian grid, I would just convert your points to UTM coordinates. The points and lengths will all be in meters then and the check should be easy. Lots of matlab code is available to do this conversion from LL to UTM. Like this.
You don't mention how long the axes of the ellipse are in the description. If they are very long (say hundreds of km), this approach may not work for you and you will have to resort to thinking about great circles and so on. You will have to make sure to specify the UTM zone to which you are converting. You want all your points to end up in the same UTM zone or you won't be able to relate the points.
After some more research into my problem and posting in another forum I was able to figure out a solution. My ellipse is relatively small so I assumed it was a true (flat) ellipse. I was able to locate the lat lon of the foci of the ellipse then if the sum of the distances from the point of interest to each focus is less than 2a (the major axis radius), then it is within the ellipse. Thanks for the suggestions though.
-Cody
In my iPhone app, suppose I have the coordinates of the current location. I want to know the coordinates of a point 10km from here, and 30° North East for example. How do I calculate it? Thanks.
After typing a bunch of formulae out, I realized there's a site that already has it down, so I'm just going to link that instead, Calculate distance and bearing between two Latitude/Longitude points. The section titled "Destination point given distance and bearing from start point" is what you want. Just convert the degrees to radians (your bearing) and you'll be all set