I using pyEphem to calculate RA/Decs of satellites and I'm confused by the different
values computed and described on
http://rhodesmill.org/pyephem/radec.html
this bit of code
sat=ephem.readtle("SATNAME ", \
"1 38356U 12030A 14148.90924578 .00000000 00000-0 10000-3 0 5678",\
"2 38356 0.0481 47.9760 0002933 358.9451 332.7970 1.00270012 3866")
gatech = ephem.Observer()
gatech.lon, gatech.lat = '-155.47322222', '19.82561111'
gatech.elevation = 4194
gatech.date = '2014/01/02 07:05:52'
sat.compute(gatech)
print 'a_ra=',sat.a_ra,'a_dec=',sat.a_dec,'g_ra=',sat.g_ra,'g_dec=',sat.g_dec,'ra=',sat.ra,'dec=',sat.dec
gives
a_ra= 0:52:40.75 a_dec= -3:15:23.7 g_ra= 1:14:10.55 g_dec= 0:06:09.8 ra= 0:53:23.57 dec= -3:10:50.5
if I change JUST the observers location to say
gatech.lon, gatech.lat = '-5.47322222', '19.82561111'
I get
a_ra= 1:15:36.95 a_dec= -2:32:29.9 g_ra= 1:14:10.55 g_dec= 0:06:09.8 ra= 1:16:19.75 dec= -2:28:04.6
I thought the observers position only came into the calculation of sat.ra and sat.dec
so was suprised to see a_ra and a_dec had changed.
What am I missing?
Thanks
Ad
Per the last paragraph of the “body.compute(observer)” section of the Quick Reference:
http://rhodesmill.org/pyephem/quick.html#body-compute-observer
For earth satellite objects, the astrometric coordinates [meaning a_ra and a_dec] are topocentric instead of geocentric, since there is little point in figuring out where the satellite would appear on a J2000 (or whatever epoch you are using) star chart for an observer sitting at the center of the earth.
And in the issue that has been opened about this behavior, the project is open to suggestions about where this text can appear more prominently to prevent future confusion for users:
https://github.com/brandon-rhodes/pyephem/issues/55
Related
I am trying to build a support structure around a cylinder in openscad, but I cannot seem to make the angled part of the structure "manifold"
inner_slide_tube_inner_radius=14.9/2;
leadpipe_wall_thickness=14.9/2;
leadpipe_length=200;
mouthpiece_receiver_large_radius=0.546*25.4/2;
NoSpokes = 4;
SpokesWide = 3;
SpokesHigh = 3;
SpokesLong = leadpipe_length/2*0.75;
SpokesLong2 = leadpipe_length/2;
//if I comment out this section, then I can render a single support angle part when NoSpokes=1
for (i=[1:NoSpokes])
rotate([0,0,360/NoSpokes*i])
translate([mouthpiece_receiver_large_radius+leadpipe_wall_thickness,-SpokesWide/2,0])
cube([SpokesLong, SpokesWide, SpokesHigh]);
//
for (i=[1:NoSpokes])
rotate([0,0,360/NoSpokes*i])polyhedron(
points=[
[mouthpiece_receiver_large_radius+SpokesLong+leadpipe_wall_thickness-SpokesHigh, -SpokesWide/2, SpokesHigh],
[mouthpiece_receiver_large_radius+SpokesLong+leadpipe_wall_thickness-SpokesHigh, SpokesWide/2, SpokesHigh],
[inner_slide_tube_inner_radius, SpokesWide/2, SpokesLong2],
[inner_slide_tube_inner_radius, -SpokesWide/2, SpokesLong2],
[mouthpiece_receiver_large_radius+SpokesLong+leadpipe_wall_thickness, -SpokesWide/2, SpokesHigh],
[mouthpiece_receiver_large_radius+SpokesLong+leadpipe_wall_thickness, SpokesWide/2, SpokesHigh],
[inner_slide_tube_inner_radius, SpokesWide/2, SpokesLong2+SpokesHigh],
[inner_slide_tube_inner_radius, -SpokesWide/2, SpokesLong2+SpokesHigh]],
faces=[[1,0,3,2],
[1,5,4,0],
[2,3,7,6],
[1,5,6,2],
[0,4,7,3],
[4,5,6,7]
]);
I know that this is really naive question, but I am rather stuck as I keep getting the warning WARNING: Object may not be a valid 2-manifold and may need repair!
Any help would be greatly appreciated to get rid of the warning.
The reason your design is not manifold is that some of your polygon don't have the correct winding order. In OpenSCAD, if you preview your design using F2 (Thrown Together), such wrongly winded polygons will be highlighted in pink.
I'm using ios-charts (https://github.com/danielgindi/Charts). I have a LineChartView with 12 values in the x axis.
This however is far too many to see at the same time, so I want to display only 5 and then let the user drag to the right to see the next.
I've tried this:
let chart = LineChartView()
chart.dragEnabled = true
chart.setVisibleXRangeMaximum(5)
let xAxis = chart.xAxis
xAxis.axisMinValue = 0
xAxis.axisMaxValue = 5.0
xAxis.setLabelsToSkip(0)
But still see all 11 values at the time. How can I only see 5?
I finally got it!
The correct answer is:
chart.setVisibleXRangeMaximum(5)
This however needs to be set after the data has been set in the chart (not in a configure before)
This did the trick for me
You should set the X axis's labelCount property of the chart view.
In objc,like this
_chartView.xAxis.labelCount = 5;
Swift
chartView.xAxis.labelCount = 5
Here is my finding!!
you don't need to really use label count
if you are using DefaultAxisValueFormatter, NEVER use this. a lot of errors pop ! just use no2.
chart.setVisibleXRangeMaximum(number) will do.
please put this after chart data setting here you can see detail
combinedChartView.data = combineData. //this need to come first
combinedChartView.setVisibleXRangeMaximum(2) //after data setting
I have a few locations in parse which I'm query-ing. It shows all annotations but it only zoom the last one. How can I find max and min latitudes and longitudes and make them fit ?
There is plenty of these on stackoverflow but they're almost all in objective-c.
The examples in Objective-C are still essentially valid since the underlying SDK/API is still the same -- just being called using a different language (and there's always the documentation).
To show all annotations, there are essentially two ways to do it:
Use the convenient showAnnotations method. You pass it an array of annotations and it will automatically calculate a reasonable region to display. You call it after adding all the annotations (after your for loop). In fact, showAnnotations will even add the annotations itself if they aren't already on the map. To show all annotations that are already on the map, just pass it the map's own annotations array. Example:
self.mapView.showAnnotations(self.mapView.annotations, animated: true)
If you are not happy with the default region calculated by showAnnotations, you can calculate one yourself. Instead of calculating minimum/maximum latitudes and longitudes, etc, I prefer to use the built-in MKMapRectUnion function to create an MKMapRect that fits all annotations and then call setVisibleMapRect(mapRect,edgePadding,animated) which lets one conveniently define padding in screen points around the fitted map rect. This technique was originally found in a very early map view sample app from Apple. Example:
var allAnnMapRect = MKMapRectNull
for object in objects! {
//existing code that creates annotation...
//existing code that calls addAnnotation...
let thisAnnMapPoint = MKMapPointForCoordinate(annotation.coordinate)
let thisAnnMapRect = MKMapRectMake(thisAnnMapPoint.x, thisAnnMapPoint.y, 1, 1)
allAnnMapRect = MKMapRectUnion(allAnnMapRect, thisAnnMapRect)
}
//Set inset (blank space around all annotations) as needed...
//These numbers are in screen CGPoints...
let edgeInset = UIEdgeInsetsMake(20, 20, 20, 20)
self.mapView.setVisibleMapRect(allAnnMapRect, edgePadding: edgeInset, animated: true)
I have everything going swimmingly on my pie chart and 3D pie charts within MATLAB for a dataset, however, I noticed that even though I have 21 pieces of data for this pie-chart being fed into the pie-chart call, only 17 appear.
PieChartNums = [ Facebook_count, Google_count, YouTube_count, ThePirateBay_count, StackOverflow_count, SourceForge_count, PythonOrg_count, Reddit_count, KUmail_count, Imgur_count, WOWhead_count, BattleNet_count, Gmail_count, Wired_count, Amazon_count, Twitter_count, IMDB_count, SoundCloud_count, LinkedIn_count, APOD_count, PhysOrg_count];
labels = {'Facebook','Google','YouTube','ThePirateBay','StackOverflow', 'SourceForge', 'Python.org', 'Reddit', 'KU-Email', 'Imgur', 'WOWhead', 'BattleNet', 'Gmail', 'Wired', 'Amazon', 'Twitter', 'IMDB', 'SoundCloud', 'LinkedIn', 'APOD', 'PhysOrg'};
pie3(PieChartNums)
legend(labels,'Location','eastoutside','Orientation','vertical')
This goes for the labels and the physical graph itself.
Excuse the poor formatting in terms of the percentage cluster, this is just a rough version. I tried every orientation and even splitting labels between the orientations without any luck.
Quasi-better resolution for Pie Chart -- Imgur Link
Like Daniel said - it appears that there simply isn't any non-negative data for the missing slices. I tried reproducing your problem with the following initialization, yet it resulted in normal-looking chart:
[ Facebook_count, Google_count, YouTube_count, ThePirateBay_count, ...
StackOverflow_count, SourceForge_count, PythonOrg_count, Reddit_count, ...
KUmail_count, Imgur_count, WOWhead_count, BattleNet_count, Gmail_count, ...
Wired_count, Amazon_count, Twitter_count, IMDB_count, SoundCloud_count, ...
LinkedIn_count, APOD_count, PhysOrg_count] = deal(0.04);
In order to verify this hypothesis - could you provide the data you're using for the chart? Do you get any warnings when plotting the chart?
From inside the code of pie.m:
if any(nonpositive)
warning(message('MATLAB:pie:NonPositiveData'));
x(nonpositive) = [];
end
and:
for i=1:length(x)
if x(i)<.01,
txtlabels{i} = '< 1%';
else
txtlabels{i} = sprintf('%d%%',round(x(i)*100));
end
end
You can see that MATLAB doesn't delete valid slices, but only renames them if the data values are small.
I can't seem to figure out how to calculate an azimuth of a star, let's say Sirius, when it is at alt=0 (star rise/star set).
So essentially in the end I will have two values.
Sirius.az # star rise
Sirius.az # star set
Is this possible?
THANKS!
Simply check the .az attribute of the star once your observer object has determined the moment of rising or setting. For example:
import ephem
s = ephem.star('Sirius')
boston = ephem.Observer()
boston.lat = '42.37'
boston.lon = '-71.03'
boston.next_rising(s)
print s.alt, s.az
boston.next_setting(s)
print s.alt, s.az
Running this script at this moment gives me the encouraging output:
0:00:00.0 112:23:25.2
0:00:00.0 247:36:34.9
As you can see, the rising and setting routines have already established the moment of zero altitude, leaving the azimuth for you to read off and use!