I have my current location from CLLocation,
and I have another location- also an CLLocation.
I would like to detect when my device is heading towards that other location.
(I can calculate the distance in meters between this points- but can't workout
the calculation of an accurate angle to compare with the device current heading)
Thanks.
How about using CLLocation's built-in course property?
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One approach could be to continuously calculate the distance between current location and target location. if the distance decreases, your device is moving towards the the target.
In a real world szenario (car in city, car in mountainous country e.g. Switzerland) this doesn't work. You would need some array of way-points (e.g. intersections) that lead towards the target and continuosly look for the closest waypoint.
Related
I've been tasked with creating a Google Earth Web link programmatically when given coordinates. I have the street address as well, where I'd ideally like to drop a pin.
For example, I can get a link to the white house using its lat/lon at a distance of 150 meters like this:
https://earth.google.com/web/#38.8976633,-77.0365739,150d
If I search using the google earth web app I can generate a link with a pin, where a few of the parameters in the link change slightly:
https://earth.google.com/web/#38.8976763,-77.0365298,18.0497095a,800.41606338d,35y,0h,45t,0r/data=ChIaEAoIL20vMDgxc3EYAiABKAIoAg
Am I able to dynamically generate the data element, or whichever element creates the pin, at my desired location? I've also had trouble finding the correct distance d and elevation a parameters in my links.
As you found, you can generate links to specific views in the Google Earth web client by adding the correct parameters to the URL, including the latitude, longitude and altitude (a) of the view target, and the distance (d) of the camera from that target. Note that altitude and distance are both in meters, and altitude is above sea level, not above ground elevation. If you look at the a and d parameters that Earth puts in the URL as you fly around, often altitude will be the terrain (or builing-top) elevation at the target lat/lon, and the distance will be how far the camera is from that altitude. The other available parameters include heading (h) and roll (r).
So long as your tilt (t) remains zero, then altitude and distance should be interchangeable, or if both are >0, then they will be summed together for the final camera height above sea level. But if you add a tilt (zero degrees is looking straight down), then the altitude determines the elevation of the view target (above the lat & lon location), and the distance determines how far the camera is from that point. If you make d=0, then altitude will define both the view target and camera height above sea level. If you make a=0, then the distance will be from the lat,lon at sea level (even if that's underground).
Unfortunately there's no way to manually construct the data parameter, as it can contain many different things. To do that right would require an API, which Earth for Web currently does not provide. Hopefully that kind of functionality will come after Earth finishes its work to become cross-browser compatible via Web Assembly. Until then, there's not a way to add a point the map via just a URL.
I made a simple app which displays the altitude according to the GPS position on iPhone.
How is the altitude obtained?
Does it get the altitude of the land at the coordinates I am or does it get the actual altitude? (I tried the same application in the same building; once at ground floor and once on the third floor but the same altitude is displayed)
Is it possible to obtain a different altitude on different floors? (Like my android phone has a barometer sensor and I calculate the elevation by the atmospheric pressure; but none of the iPhones has a barometer sensor)
The altitude as read by the gps receiver depends on the positions of the satellites over the horizon, relative to each other. It is possible then for the altitude reading to be unreliable when either there are not enough satellites in the sky or they are too close together. This then depends on the time of day, or date.
The signals from the satellites are very weak once they have reached the Earth's surface, and may not be received correctly inside buildings, or where there are other tall buildings nearby, such as a city centre like Manhattan.
Barometer readings will vary according to the weather and so an absolute reading can't be applied to a specific floor. However relative readings may be reliable enough for floor to floor changes, e.g. a lower value means going up.
Like any other device that uses GPS to calculate altitude, it's measuring the user's distance from the center of the satellites' orbits.
Your smartphone uses GPS technology to calculate your altitude depending on where you are. It measures how far away you are from the satilites which is calculating this information.
Note that newer IPhones (>= 6) have a barometer sensor which in my experience is significantly more accurate than GPS. With a barometers the accuracy appears to be within a foot whereas with GPS it would bounce around by 3-4 meters even when standing still.
http://www.iphonetricks.org/iphone-6-barometer-sensor-features/
I am developing a project in augmented reality where a compass shows the direction to the destination.That works fine but i want to check whether the current heading is pointing towards the destination or not.
Can any one suggest me a method to do it?
I have searched a lot in Google couldn't find any method?
Thanks in advance
You need the absolute bearing from your location to your target location
Unfortunately CLLocation doesn't have a call for this but you can find the algo in this question.
CLLocation Category for Calculating Bearing w/ Haversine function
So lets say the bearing is 90 degrees
Then you get the phone bearing to north.
While you are getting location updates you also have course update with CLLocation.
The course might also be 90 degrees
SO find the difference between the two, 90 - 90 = 0! you are dead on target :) You will need to rationalise the numbers to 0 - 360 in the event say you are facing north (0 degrees) and your target is behind you (180 degrees) resulting in -180. If you end up with a negative number just add 360.
I find the magnetic field compass to be very very fidgety, so it looks much nicer if you have some sort of exponential moving average for changes in the phones bearing.
I'm building an augmented reality game, and working with CLLocation is rather cumbersome.
Is there some way to locally approximate CLLocation as XYZ coordinate, expressed in meters with the origin starting at some arbitrary point (for example the initial position when the game was started)?
Lets say I'm working with a 1 mile radius and do not really care about the curvature of the earth. Is it possible to approximate or somehow simplify the location based calculations for local position tracking?
Alternatively, is there a coordinate system that can be used with CLLocation that also incorporates the roll, pitch, yaw of the CMAttitude as well as compass orientation?
Clarification: As far as I understand, the problem with latitude and longitude is that their units vary in size, depending on the position on the globe. I should've specified that X,Y,Z should be in standard units, like meters or feet.
Thank you!
The Haversine formula may be useful.
I found a good article on it at http://www.jaimerios.com/?p=39 with code examples.
You could get the initial point at the app's launch and calculate the relative points based on the user coordinates as he or she moves. Admittedly, this is not super elegant, but if you are just trying to do some simple comparisons based on the user's location relative to an arbitrary origin, this should work. For the Z, Alex Stone's suggestion of calculating it based on the altitude should be fine.
I'd like to know (from a high level view) what would be required to take a pdf floor plan of a building and determine where exactly you are on that floor plan using GPS coordinates? In addition to location, the user would be presented with a "turn by turn" directions to another point on the map, navigating down hallways, between cubicles, etc.
Use case: an iPhone app that determined a user's location and guided them to a conference room or person's office in the building.
I realize that this is by no means trivial, but any help is appreciated. Thanks!
It's an interesting problem. When you're using Core Location, you're not necessarily using GPS. Using WiFi and cell tower triangulation, you can get pretty good location results. So from Core Location you get a latitude and longitude fix. (You might also get altitude info, since GPS data is 3-dimensional. You also will get an accuracy value.)
So you have lat and lon. You need to map these coordinates to the PDF plan's coordinates. Assuming that the plan is aligned with the latitude and longitude lines, and that you have a lat-long fix for one of the points on the plan, you need to calculate the x-axis scale and y-axis scale. Then it's some calculations to map the lat-long to x-y coordinates on the PDF plan.
GPS may not be accurate enough for this purpose, especially indoors. Assuming errors on
the order of 10 meters, you'll have difficulty determining which floor the user is on.
Here's a neat (?) idea that might work: can you post some "You are here" placards
at various locations around the building? You could label each one with a unique,
machine-readable location code (maybe a QR code or something similar), then take an
image using the camera, have your app read that image and interpret the location code,
and use that instead of GPS to determine the start location.
GPS inside? That's your first -- and biggest -- hurdle.
Next hurdle is knowing the GPS coordinates of at least three points on that PDF to define the plane of of your map in the real world. (The PDF will need to be to scale, of course.)
So that gives you where you are on the PDF. Now you'll need to figure out some way to determine where you can walk (or where you can't) to get directions.