I need to represent on the map (iPhone) some points such as (88, 60) or (90, 55), but the custom annotations representing these points get deallocated. I also noticed that these points are not actually displayed on the google map, they are somehow above the visible map. This happens for any point that is above 85 deg. N latitude or -85 deg. S latitude.
I know it's a really old post, but just to answer your question.
Most (allmost all) commercial maps are displayed in the mercator projection. This is what you see in mapKit or on google maps. This means that the latitude and longitude lines run horizontal and vertical.
If you would change this to for instance polar project (world from the top) it would become way to difficult to calculate the postion of objects because the lat and long lines converge rapidly...
So it's just for ease of use....
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.
Seems like a simple question, but I have been tearing my hair out for hours now.
I have a series of files ie.
kml_image_L1_0_0.jpg
kml_image_L2_0_0.jpg
kml_image_L2_0_1.jpg
kml_image_L2_1_0.jpg
kml_image_L2_1_1.jpg
etc. However just plotting them on the leaflet map surface understandibly puts the images at 0,0 on the earths surface, and the 0 zoom level inferred by the files should really be about 15 or so.
So I want to specify the latitude and longitude where the images should originate , and what zoom level they should start at. I have tried bounds (which doesn't display anything) and I have tried playing with offsetting the zoom level.
I need this because a user needs to click on an offline map to specify where they are and I need the GPS coordinates.
I also have a KML file but it seems to be of more help for plotting vector data on the map.
Any help is much appreciated, cheers.
If I understand correctly, the "kml_image_Lz_x_y.jpg" images that you have are actually tiles, with zoom, horizontal and vertical indices in their file name?
And your issue is that they use (z,x,y) numbers as if they started from the top-most level (zoom 0, single tile for entire world), but in fact they are just a small portion of the pyramid of tiles?
And you cannot use them as is because you still want to get actual geographic coordinates (latitude, longitude), which would be totally wrong if you used the tiles as if they were showing the entire world?
In that case, you have several options as workarounds:
The most simple and reliable would probably be to simply write a small script to rename all your tiles to their true (z,x,y) numbers.
Another option would be to modify the (z,x,y) numbers before they are written in the tile src attribute, and apply the appropriate offset (constant for z, scaled by z for x and y). That should probably happen in L.TileLayer.getTileUrl() method.
Good luck! :-)
I would like to create a MKCoordinateRegion (to zoom to the good region on the map) from the northeast and southwest points given by Google. For that I need to compute the coordinate of the center between these two coordinates. Any clue? I could do simple math but I will have problems with the equator...
Thanks!!!
Assuming you mean anti-meridian and not the equator then here goes (While all this works on a flattened map and should be good enough for your purpose, it's completely bung on a sphere. see note at the bottom).
What I've done in other cases is start at either point, and if the next point is more than 180 degrees to the east, I convert it so that it is less than 180 to the west like so
if(pointa.lon - pointb.lon > 180)
pointb.lon += 360:
else if (pointa.lon - pointb.lon < -180)
pointb.lon -= 360
At this time pointb.lon might be an invalid longitude like 190 but you can at least work out the mid-point between pointa and point b because they will be on a continuous scale, so you might have points 175 and 190. Then just get the mid-point between them as 182.5, then convert that to make sure it is within the usual limits and you get -177.5 as the latitude between the two points. Working out the latitude is easy.
Of course on a sphere this is wrong because the midpoint between (-180,89) and (180,89) is (0*,90) not (0,89).
* = could be anything
Also, couldn't you just zoomToRect made with the defined corners? It'd save you doing this calculation and then next one which would be to work out what zoom level you need to be at when centered on that point to include the two corners you know about. Since the Maps app doesn't appear to scroll over the anti-meridian I assume MKMapview can't either so your rectangle is going to have to have the northeast coord as the top right and the southwest as the bottom left.
This SO post has the code to zoom a map view to fit all its annotations.
I want to now how to convert longitude, latitude to its equivalent xy coordinate components in iPhone programming. (I am using only CoreLocation programming, and want to show a point on iPhone screen without any map).
thanks
Well the exact conversion depends on exactly which part of the Earth you want to show, and the stretching along longitude varies according to latitude, at least in Mercator.
That being said, even if you don't want to display an actual MapKit map, it would probably be easiest to create an MKMapView and keep it to one side. If you set the area you want to display appropriately on that (by setting the region property), you can use convertCoordinate:toPointToView: to map from longitude and latitude to a 2d screen location.
Note that MKMapView adjusts the region you set so as to make sense for the viewport its been given (eg, if you gave it a region that was a short fat rectangle, but the view it had was a tall thin rectangle, it'd pick the smallest region that covers the entire short fat rectangle but is the shape of a tall thin rectangle), so don't get confused if you specify a region with the top left being a particular geolocation, but then that geolocation isn't at the exact top left of the view.
I'm familiar with using Google Maps Javascript API. Recently I started using MapKit framework for an iphone project, but I'm having a hard time to figure out zooming and setting a region on map.
In Google Maps API I used to use integer zoom levels like 8, 9, 10 along with straightforward function setZoom(). The only equivalent method I can see in the MapKit framework is setRegion:animated. As I understand, I need to set a region's span's latitude and longitude "delta" values to specify zoom level. But I really don't have an idea what these values represent(I read the documentation).
When I use a MKMapView delegate and trace the span values in regionDidChange delegate method results don't seem to correlate each other. It's ok when I zoom out and see the span delta values are increasing as specified in documentation. But suddenly I drag the map without zooming and delta values become 0.0.
Can somebody please explain what is the reference point to these span and delta? Or is there any algorithm to convert an integer zoom level(like 9) to these delta values?
As a bonus question is there any way to specify a minimum-maximum zoom level on a MKMapView :)
Thanks
First of all, MKMapView does not use/have a predefined set of zoom levels like Google Maps does.
Instead, the visible area of a MKMapView is described using MKCoordinateRegion, which consists of two values:
center (the center point of the region), and
span (the size of the visible area around center).
The center point should be obvious (it's the center point of the region.)
However, span (which is a MKCoordinateSpan) consists of:
latitudeDelta (the vertical distance represented by the region), and
longitudeDelta (the horizontal distance represented by the region).
A brief example. Here's a toy MKCoordinateRegion:
center:
latitude: 0
longitude: 0
span:
latitudeDelta: 8
longitudeDelta: 6
The region could be described using its min and max coordinates as follows:
min coordinate (lower left-hand point):
latitude: -4
longitude: -3
max coordinate (upper right-hand point):
latitude: 4
longitude: 3
So, you can specify zoom levels around a center point by using an appropriately sized MKCoordinateSpan. As an approximation of Google's numeric zoom levels, you could reverse engineer the span sizes that Google uses for a given zoom level and create a span, accordingly. (Google describes their view regions in the same way that MKMapView does, as a center + span, so you can pull these values out of Google Maps.)
As for restricting the region, you may play w/ this delegate method:
mapView:regionWillChangeAnimated
e.g. by resizing the region back into your allowed zoom levels. (Kind of like how table views will let you scroll past the edge, but will then rubber band back into place.) However, your mileage may vary, since I haven't used it for this purpose.
btw, there are definite fixes/improvements in OS 3.1 to aspects of MapKit that were giving me trouble in 3.0.
If you prefer using explicit zoom levels instead of defining an MKCoordinateSpan, I wrote a category that adds support for specifying the zoom level of an MKMapView. The code can be found here.
The span is in degrees of latitude and longitude. There is a method for constructing MKCoordinateRegion structs that takes distance, instead. It may be that you are using MKCoordinateRegionMakeWithDistance to specify the span, and then when you check it in regionDidChange, you're seeing at the lat/long span, which is how it is stored in an MKCoordinateRegion struct.
As far as I know, the integer zoom levels are not available or useful at all when working with MKMapKit. I personally prefer using the span figures, its more flexible.
You cannot specify max and min zoom, and I don't know of a way to hack it in. MKMapKit is actually pretty weak right now, I'm pretty disappointed by the lack of features.
A quick comparison of zoom levels for a location using maps.google.com by inspecting the link querystring shows that the dx and dy span values increase by a factor of 2:
(0.005334, 0.011834) starting span
(0.010668, 0.023668) dx: x2, dy: x2
(0.021335, 0.047337) dx: x2, dy: x2
(0.042671, 0.094671) dx: x2, dy: x2
...
Brant's category on MKMapView works well. However, it appears that it has not been updated to support newer devices with retina screens when calculating mapSizeInPixels.
It can be fixed by replacing this line:
CGSize mapSizeInPixels = mapView.bounds.size;
With this line:
CGSize mapSizeInPixels = CGSizeMake(mapView.bounds.size.width * [UIScreen mainScreen].scale, mapView.bounds.size.height * [UIScreen mainScreen].scale);