I need to draw a circle of a radius 1.23 metre on MkMapView using MKCircle.
How would i show that on the map.
I used the following ,
r = 1.23;// in metres.
circle = [MKCircle circleWithCenterCoordinate:location radius:r];
But when i draw it on the map it looks like more than 1km on the MKMapView.
Could someone please tell me how i could represent a circle of radius 1.23 metre on the map??
This is mainly to show the accuracy of the location, so the radius indicates the accuracy of the location.
In the viewForOverlay delegate method, try setting the lineWidth of the MKCircleView to 1.
I think the default width of 0 results in the "road width".
MKCircle class definition says
radius
The radius of the circle, measured in meters from the center point.
So your code should work fine.
Source: http://developer.apple.com/library/ios/#DOCUMENTATION/MapKit/Reference/MKCircle_class/Reference/Reference.html
Related
I have a leaflet circle with a radius, how do I convert the radius to nautical miles in javascript?
Note that for Leaflet's circle, the radius corresponds to meters (see L.circle). Then you can convert meters directly into nautical miles.
Note that L.circle is just an approximation:
It's an approximation and starts to diverge from a real circle closer to poles (due to projection distortion).
To draw a gedetically accurate circle, use something like Leaflet.Geodesy.
A quick JS function to convert meters to miles -
function metersToMiles(meters){
if (isNaN(meters)){
console.log("meters is not a number");
return 0;
}
return meters/1852;
}
Also a good thing to note is that the draw tools for leaflet.draw have a way to draw a circle with nautical miles as the unit of measure -
draw: {
circle: {
metric: false,
feet: false,
nautic: true
}
}
leaflet draw documentation link
It looks like there is a "readableDistance" on the L.GeometryUtil object too but I only used the code above so I am not sure how that would work.
i have a circle and a point on it in matlab :
center = [Xc1 Yc1];
circle = [center 150];
point=[ 54.8355 116.6433]
I want to partition this circle into 8 arc and find out which arc is this point in ? how can i do this in matlab?
(i used this code to draw circle :
http://www.mathworks.com/matlabcentral/fileexchange/7844-geom2d/content/geom2d/geom2d/intersectLineCircle.m)
Dividing a circle into 8 arcs can be stated another way: cutting a pie into 8 pieces. These pie pieces each have an angle of 360/8 = 45 degrees. You can then think of the circle being broken up into these angle ranges (in degrees):
[0,45)
[45,90)
[90,135)
[135,180)
[180,225)
[225,270)
[270,315)
[315,0)
You'll have to then calculate the angle between the line that is made when you connect your point to the center of the circle and the x-axis. When you calculate this angle, you'll see which 'angle bin' it belongs to.
I have to display 5x5 degrees pie chart on a leaflet map. I can display pie chart using the great leaflet-dvf library, but I have to provide the radius in pixel, and it is static so far.
I would like to have it dynamic so that at any zoom level, the pie chart fills the 5x5 square (aka radius = 5x5 degree length).
How can I know the length in pixel of the side of a 5x5 degrees square, depending on the zoom level?
Thanks
This will work out metres per pixel
metresPerPixel = 40075016.686 * Math.abs(Math.cos(map.getCenter().lat / 180 * Math.PI)) / Math.pow(2, map.getZoom()+8);
I used the following page that provides the pixel per meter on a leaflet map depending on the zoom level:
http://wiki.openstreetmap.org/wiki/Zoom_levels
Then I computed the length of a 5x5 square at the equator: 556000 meters.
Then I store the length ratio for zoom level = 0:
$scope.lengthRatio = 556000 / 156412 // in meter / pixel
Finally, I get the radius of a pie chart depending on the zoom level ($scope.mapZoom):
var radius = $scope.lengthRatio * Math.pow(2,$scope.mapZoom)) / 2
The /2 is because I want the radius and not the diameter
Simple!
I'm attempting to draw a circle around a point on a mapview, which I have successfully done, but not quite the way I wanted to. The CG methods are always going to be drawing relative to the screen size, and basically I want to draw things in meters, not pixels.
Anyone have experience doing this?
I don't have any experience doing what you describe above, but the MKMapView class has a set of methods for concerting Pixels to Coordinates and vice versa that you should be able to use to map your circle to Coordinates on the Map:
http://developer.apple.com/iphone/library/documentation/MapKit/Reference/MKMapView_Class/MKMapView/MKMapView.html#//apple_ref/occ/instm/MKMapView/convertCoordinate:toPointToView:
This function may also come in handy for finding a point on the diamater of your circle to use with the above functions, providing you have your center point, the radius in meter of the circle, and the bearing in degrees.
-(CLLocation*) offsetLocation:(CLLocation*)startLocation:(double)offsetMeters:(double)bearing
{
double EARTH_MEAN_RADIUS_METERS = 6372796.99;
double lat2 = asin( sin(startLocation.coordinate.latitude) * cos(offsetMeters/EARTH_MEAN_RADIUS_METERS) + cos(startLocation.coordinate.latitude) * sin(offsetMeters/EARTH_MEAN_RADIUS_METERS) * cos(bearing) );
double lon2 = startLocation.coordinate.longitude + atan2( sin(bearing) * sin(offsetMeters/EARTH_MEAN_RADIUS_METERS) * cos(startLocation.coordinate.latitude), cos(offsetMeters/EARTH_MEAN_RADIUS_METERS) - sin(startLocation.coordinate.latitude) * sin(lat2));
CLLocation *tempLocation = [[CLLocation alloc] initWithLatitude:lat2 longitude:lon2];
return tempLocation;
}
I wanted to test the mapKit and wanted to make my own overlay to display the accuracy of my position.
If i have a zoom factor of for example .005 which radius does my circle around me has to have(If my accuracy is for example 500m)?
Would be great to get some help :)
Thanks a lot.
Look at the documentation for MKCoordinateSpan, which is part of the map's region property. One degree of latitude is always approx. 111 km, so converting the latitudeDelta to meters and then getting to the meters per pixel should be easy. For longitudinal values it is not quite so easy as the distance covered by one degree of longitude varies between 111 km (at the equator) and 0 km (at the poles).
My way to get meters per pixel:
MKMapView *mapView = ...;
CLLocationCoordinate2D coordinate = ...;
MKMapRect mapRect = mapView.visibleMapRect;
CLLocationDistance metersPerMapPoint = MKMetersPerMapPointAtLatitude(coordinate.latitude);
CGFloat metersPerPixel = metersPerMapPoint * mapRect.size.width / mapView.bounds.size.width;
To add to another answer, a difference of one minute of latitude corresponds to one nautical mile: that's how the nautical mile was defined. So, converting to statute miles, 1 nautical mile = 1.1508 statue miles, or 6076.1 ft. or 1852 meters.
When you go to longitude, the size of the longitude circles around the Earth shrink as latitude increases, as was noted on the previous answer. The correct factor is that
1 minute of longitude = (1852 meters)*cos(theta),
where theta is the latitude.
Of course, the Earth is not a perfect sphere, but the simple calculation above would never be off by more than 1%.