I am trying to create a custom map for iOS. For the time being I am using Openstreetmap images for the custom map app.
Now what I want is to convert the pixel point to Latitude and Longitude value at a particular zoom level. I am finding out the tile(pixel point) in which I clicked. I need to find out the Lat and Long of that particular point. How this can be calculated? Is there any general formula to find the Lat & Long from pixel point.
Thanks in advance
Do you know about route-me (https://github.com/route-me/route-me)? It is an open source iOS map library. I use a fork of this library found at https://github.com/Alpstein/route-me. These libraries provide the projections you are looking for and might even provide other functionalities you would have to implement yourself otherwise.
Related
I'm working on an application for Android & iOS to show points of interest over the camera. ARkit & ARcore has poor compatibility nowdays.
Could you recommend me some library to do this? If it comes with an example, better! I know viro-media, but I don't understand how to do this using that library.
I don't want 3D models, just markers over the camera, similar to the attachment image.
To do this with Viro React -- and in AR in general -- the trick is to recognize that there are two coordinate systems:
The local coordinate system of your device, which we'll call 'AR space'. In Viro, this is centered at the user's initial position when the application starts, and is in meters.
Geographic coordinates (latitude and longitude).
To position the overlays, you have to convert your content from geographic coordinates into AR space. This is a two-step process. First project the spherical geographic coordinates onto a 2D plane -- the Web Mercator is great for this. Then translate the projected coordinates by the device's initial projected position.
The device's initial projected position can be derived by projecting its initial geographic position. In Viro React, you can use the Geolocation module to grab this when the user starts the app.
Finally, you'll need to do a similar transformation for the user's bearing: converting from compass direction to device orientation in AR space.
For this to work well you'll likely have to figure out how handle inaccurate geolocation lookups (e.g. what happens if the location retrieved from the device is inaccurate), and may also have to account for drift: over time the two coordinate systems may start to fall out of sync.
The last part, creating the info cards, is easy with Viro -- you either pre-bake the images with text and use ViroImage, or if the cards need to be more dynamic you can use a ViroFlexView.
I am also interested in this one and I'm trying out ViroReact!
I find a bit difficult to understand how to make this work when the lat's and long's have been converted to x-y-values. What should the z-value be?
Let's say you have the lat-lon coordinates [59, 10] as the user location you want to show where [59, 11] is relative to your location. How to you build that in a ViroARScene?
<ViroNode position={ **userLocationFromLatLonCartesian** }>
<ViroBox position={ **poiLocationFromLatLonToCartesian** }/>
</ViroNode>
So how do you calculate the scale, position and rotation, so that the object will be visible?
Seem like https://github.com/proj4js/proj4js is a library that could provide conversions from latlon to x-y values
I found that both android and ios AR sdk support location base AR View refererence:
https://developers.google.com/ar/develop/ios/geospatial/quickstart and https://developer.apple.com/documentation/arkit/argeoanchor
I'm working on a compass app and need to find current direction to a particular point (I have coordinates), or at least to the north. How can I do that?
Thanks.
For those who faced the same problem:
1) get access to magnetometer and accelerometer of a device. For that you can either write your own react-native <-> java/swift/objC bridge or use one of libraries like these:
github com/pwmckenna/react-native-motion-manager
github com/kprimice/react-native-sensor-manager
2) convert meters' data to compass heading.
Some informations is here:
https://cdn-shop.adafruit.com/datasheets/AN203_Compass_Heading_Using_Magnetometers.pdf
3) If there is a need to find direction to some particular point, first you need to get your own coordinates and then adding that to point's coordinates you can find out azimuth.
It does not support, but you can simply render a polyline annotation from your direction result.
First off, I am not sure if this is the right place so I apologize if this belongs elsewhere - please let me know if it does. I am currently doing some prototyping with this in VB so that's why I come here first.
My Goal
I am trying to make a program to be able to log different types of information for a video game that I play. I would like to be able to map out the entire game with my program and add locations for mobs, resources, etc.
What I have
The in game map can be downloaded so I have literally just stuck this in as a background image on the form (just for now). The map that I get downloaded though is not exactly as the map appears in the game though since the game will add extra water around everything when scrolling around. This makes it a bit tricky to match up where the origin for the map is in game compared to where it would be on the downloaded map.
The nice thing though is that while I am in the game I can print my current coordinates to the screen. So I thought that maybe I can somehow use this to get the right calculation for the rest of the points on the map.
Here is an example image I will refer to now:
In the above map you will see a dotted bounding box. This is an invisible box in the game where once you move your mouse out of the longitude and latitude points will no longer show. This is what I refer to above when I mean I can't find the exact point of origin for the in game map.
You will also see 2 points: A and B. In the game there are teleporters. This is what I would use to get the most accurate position possible. I am thinking I can find the position (in game) of point A and point B and then somehow calculate that into a conversion for my mouse drag event in VB.
In VB the screen starts at top-left and is 0,0. I did already try to get the 2 points like this and just add or subtract the number to the x and y pixel position of the mouse, but it didn't quite line up right.
So with all this information does anyone know if it is possible to write a lon/lat conversion to pixels based on this kind of data?
I appreciate any thoughts and suggestions and if you need any clarification of any information I have posted please let me know and I will be happy to expand on it. I am really hoping I can get this solved!
Thanks!
EDIT:
I also want to mention I am not sure if there is an exact pixel to lat/lon point for the in game map. I.e. the in game map could be 1 pixel = 100 latitude or something. So I might also need to figure out what that conversion number is?
Some clarifications about conversion between the pixel location to 'latitude and longitude'.
First the map in your game is in a geometry coordinate system, which means everything lies in 2D and you can measure the distance between two points by calculate the pixel position.
But when we talk about longitude and latitude, we are actually talking about a geography coordinate system, which is a '3D' model of the sphere oabout the surface of the earth. All the maps on earth are abstracted from 3D to 2D through one step called projection. Like google maps or your GPS. In this projection process, the 3D model converted to 2D model but there is always some part of the map will be tortured, so that same distance in pixels on a map could be different in length in reality.
So if you don't care about the accuracy then you can consider the geometry point as geography point. Otherwise, you need to implement some GIS library to handle the geodesic distance and calculate the geography point based on the projection coordinate system.
Currently I manage to get the direction degrees using below code:
d = Math.Atan2(Math.Sin(long2 - long1) * Math.Cos(lat2), _
Math.Cos(lat1) * Math.Sin(lat2) - Math.Sin(lat1) * Math.Cos(lat2) * Math.Cos(long2 - long1))
Dim direction As Double = (RadToDeg(d) + 360.0) Mod 360
which, in my case let say I got 250.65°
I assign each of the direction values from 0 to 360 to its particular image from imageList which loaded in the pictureBox. (currently I have 36 compass images with different arrow direction, each represent 10 degrees)
When my device is pointed to the north, the arrow image is showing the correct direction, but when when I rotate the device (pointed to anywhere which is not north), the arrow image doesn't change, means it is not showing the correct direction anymore.
So my question is, is it possible to know in which direction the gps device is pointed?
Edit: I'm using Honeywell Dolphin 6000 Scanphone device
The Honeywell Dolphin 6000 documentation doesn't mention a magnetometer or compass, so you're probably SOL. But, if it does have one, then you should be able to find methods to access it in the SDK
I recommend downloading and reviewing any APIs and documents that come with the SDK and look for references to the magnetometer or compass. Microsoft does not have standard APIs to access those sensors in Windows Mobile, so you will need the SDK from Honeywell to get that information.
If I am reading your question correct, it sounds like you are trying to determine a heading when your position is fixed and you are only rotating the device.
Unfortunately, what you are looking for is not possible with GPS.
Both the formula you are using and the GetPosition.Heading is a calculated heading based on sampling your current Latitude/Longitude and your previous Latitude/Longitude. So if you aren't moving in a direction (or moving extremely slowly), your current & previous Latitude/Longitude values will effectively be the same, which reduces that accuracy of the calculated heading.
The only reliable way to get a heading when your position is relatively fixed is to get a magnetic or gyroscopic compass, which some devices to have built in.
"how to know gps device point at which direction?"
by using GPS Intermediate Driver, GetPosition.Heading will give you the current direction you are heading.
As stated in the GPS_POSITION documentation,
"flHeading
"Heading, in degrees. A heading of zero is true north."
You must distinguish between the direction you are moving, that is called bearing or course.
And the direction you are looking or holding your device. (Think of you sitting in a bus that drives north (course = 0°), where you make a photo in direction west. heading = 270°)
A (consumer-) GPS receiver always returns only the course (or bearing), although some API unfortunatley call it heading sometimes.
To know the direction in wich you are holding your device while standing still, you have to use the magnetometer. Some modern smartphones, like iPhones or androids have that build into.
Additonal hint:
If your device has GPS, do NOT calculate the position via your or other formulas, better take the value from the GPS Api. This is much more acurate. The GPS chip does NOT only caluclate the direction by positional change, it also may use physical doppler shift.
I have compiled a list of locations with latitude and longitude information. Can I check what is the best approach to filter and populate the list of "nearest" geolocations in a table and mapview based on my current location? (or a destination entered by a user). Also is it also possible to indicate what is the radius I am interested in? e.g. only select all the nearest bookstores within 5km from my location etc
Appreciate your advice on this
Zhen Hoe
Maybe I'm missing something, but why don't you just add your locations to a mapView, and center the map on the user's current location or whereever they want? MapKit will do all the calculations for you, and only show the ones near the center. The user can set their own radius by zooming in and out. MapKit is highly optimized for exactly this purpose, that's how you can see the "rain of pins" in real time.
Update:
You can also go the other way: once you have the annotations on the map, you can query the map for those annotations that are in the visible region with:
- (NSSet *)annotationsInMapRect:(MKMapRect)mapRect
From the docs:
This method offers a fast way to retrieve the annotation objects in a particular portion of the map. This method is much faster than doing a linear search of the objects in the annotations property yourself.
You may find - (CLLocationDistance)distanceFromLocation:(const CLLocation *)location to be very useful
http://developer.apple.com/library/ios/documentation/CoreLocation/Reference/CLLocation_Class/CLLocation/CLLocation.html#//apple_ref/occ/instm/CLLocation/distanceFromLocation:
The haversine formula is frequently used to in navigation for calculating distances between coordinates. This is a pretty decent resource for distance calculations, and even has a code sample for haversine (though it is in Javascript).
If your list of locations is relative small (hundreds, even), you can probably just iterate through the whole list and calculate the distance between each place against current location.