currently, i have a table with locations (latitude, longitude). I calculate nearby calculations using sin, cos as described here
This seems rather slow. I am having the idea of pre-calculating the distance to a fixed point f and store it along the locations. When I now want to find locations nearby i just calculate distance to the same fix point and can then find them by doing some less or equal comparing.
Does my idea make sense? Is there a standard way to do that? I am in the thinking phase, so i do not have any code to show yet.
Your idea won't work unless all your locations are collinear, which most probably is not the case.
Are you using SQL to do the calculations? Are you properly using indexes? Maybe you could share a bit of your code with us.
I am developing a location-based application in which I need to get nearby location name of any geopoint selected by user. I'm using Google Places API which is working fine for me.
Only problem is the service returns null for geopoints in water. Is there any way that I can retrieve nearby locations for a geopoint in water or ocean?
AFAIK the API has no way to do that.
So, you've got two options, in order of the effort it takes:
When user taps water just throw a dialog saying "Please select a
point on land". Next to no effort and will slightly annoy the user.
Try to find the closest land geopoint yourself and use it to run the API request on
(instead of the original point). Below are some ideas on that.
A good approach can be based on this answer: basically you can get a KML file with land polygons. For performance reasons, you can simplify the polygons to the extent that makes sense for your zoom levels. Now if your point is in one of those polygons -- it's sea. And you can simply iterate over all polygon edges and pick the one that's closest to your point, then pick a point on it - again closest to your point - and do one little epsilon-sized step towards the outside of the polygon to get a land point you can do a geocode request on. Also, the original author suggests you can use Haversine formula to determine neares land point -- I'm not really familiar with the appliance of that one.
The downside is, you have to deal with KML, iterate over a lot of polygons and optimize them (and lose precision doing that, in addition to possible differences between marineregions.org data and Google Places data)
Another cool trick you could try is using Sobel Filter [edge detection] on the visible map fragment to determine where coastline is (although you will get some false positives there), then trace it (as in raster->vector) to get some points and edges to calculate the closest land position with, in a manner similar to the former approach. Here's a clumsy drawing of the idea
For Sobel edge detection, consider GPUImage lib -- they have the filter implemented and it's probably going to work crazy fast since the lib does all the calculations on GPU.
UPD Turns out there's also a service called Koordinates that has coastline data available, check the answer here
I have set up a system that calculates the distance between two locations using http://www.rubygeocoder.com/, however, to be able to calculate the (tax-deductible) kilometer-costs (e.g travel compensation) I would need to get distance by road, for example by using Google.
How is this best done?
You can use https://developers.google.com/maps/documentation/directions/.
For example a request to:
http://maps.googleapis.com/maps/api/directions/json?origin=Toronto&destination=Montreal&sensor=false
will get you the directions from Toronto to Montreal and along with it the total distance.
https://github.com/apneadiving/Google-Maps-for-Rails wraps the directions API so you might find that it makes your life easier. You might also find that it is overkill in this case since we're only talking about a single request.
I have the longitude and latitude and the name of the place I want to look for. How do I edit the Google Maps URL so that I obtain all the places (name of the places) near a set of coordinates?
I know I could do this using Google Map API, but just for a link seems a lot of trouble.
You can use the query parameter ll for your lat and long, and you can use the query parameter q for what you want to search.
http://maps.google.com/?ll=39.774769,-74.86084
Or you can
http://maps.google.com/?q=your+query
Yeah, I had the same question for a long time and I found the perfect one. Here are some parameters from it.
https://maps.google.com/?parameter=value
q=
Used to specify the search query in Google maps search.
eg :
https://maps.google.com/?q=newyork or
https://maps.google.com/?q=51.03841,-114.01679
near=
Used to specify the location instead of putting it into q. Also has
the added effect of allowing you to increase the AddressDetails
Accuracy value by being more precise. Mostly only useful if q is a
business or suchlike.
z=
Zoom level. Can be set 19 normally, but in certain cases can go up to 23.
ll=
Latitude and longitude of the map centre point. Must be in that order. Requires decimal format. Interestingly, you can use this without q, in which case it doesn’t show a marker.
sll=
Similar to ll, only this sets the lat/long of the centre point for a business search. Requires the same input criteria as ll.
t=
Sets the kind of map shown. Can be set to:
m – normal map
k – satellite
h – hybrid
p – terrain
saddr=
Sets the starting point for directions searches. You can also add text into this in brackets to bold it in the directions sidebar.
daddr=
Sets the end point for directions searches, and again will bold any text added in brackets.You can also add "+to:" which will set via points. These can be added multiple times.
via=
Allows you to insert via points in directions. Must be in CSV format. For example, via=1,5 addresses 1 and 5 will be via points without entries in the sidebar. The start point (which is set as 0), and 2, 3 and 4 will all show full addresses.
doflg=
Changes the units used to measure distance (will default to the standard unit in country of origin). Change to ptk for metric or ptm for imperial.
msa=
Does stuff with My Maps. Set to 0 show defined My Maps, b to turn the My Maps sidebar on, 1 to show the My Maps tab on its own, or 2 to go to the new My Map creator form.
reference : http://moz.com/ugc/everything-you-never-wanted-to-know-about-google-maps-parameters
additional info:
http://maps.google.com/maps?q=loc:
put in latitude and longitude after, example:
http://maps.google.com/maps?q=loc:51.03841,-114.01679
this will show pointer on map, but will suppress geocoding of the address, best for a location without an address, or for a location where google maps shows the incorrect address.
As of Jan 2018 (update: still works in May 2022) the latest URL is:
https://google.com/maps/search/*your search string* (address, landmark, city, etc. Spaces are ok)
Examples:
https://google.com/maps/search/empire state building
https://google.com/maps/search/1600 Pennsylvania Ave NW, Washington, DC 20500
You can use the new URL for Google Maps: https://www.google.com/maps/#39.774769,-74.86084,18z
equivalent to http://maps.google.com/?ll=39.774769,-74.86084.
39.774769 is the latitude and -74.86084 is longitude and 18z is 18 zoom level.
Google now has a documentation page dedicated to Maps URLs:
https://developers.google.com/maps/documentation/urls/guide
An API key is not required.
Manipulating one of the examples, I came up with this URL scheme that fits your question:
https://www.google.com/maps/search/<search term>/#<coordinates>,<zoom level>z
A valid example of this would be:
https://www.google.com/maps/search/pizza/#41.089988,-81.542901,12z
This should show you all of the pizza places around Akron, Ohio.
my Application is given a list of Geocorrdinates and now I have to determine which of those Coordinates are inside a defined Area. For example the Search would definiton would be: Show me all Areas where 100 Coordinates are in an Area of 1km^2. So I have to find out which of these coordinates are together in Areas of 1km^2 and more than 100.
But that seems to be a hard Job for my understanding of geocoordinates and I hope someone can help me with that.
The Latitude coordinates are consistent and Distance between two degrees is 111km. For example the Distance between N50,985° and N50,995° is 1,11km. The Distance between 2 Longtitude Coordinates is not so easy and depends on the Latitude coordinate.
But to be honest, I really don't know how to start.
Does someone have an Idea and can help me?
Thank you
twickl
what you need is a geospatial database, I'd recommend PostgreSQL with PostGIS. It provides the function you need to calculate this kind of stuff. Also search for good tutorials about it. An example is a radius search like "give me all McDonalds in a radius of 10km where I live"
If the problem with having a database is simply that you don't want to host it (or pay for someone to host it) then I recommend Fusion Tables.
I don't know if it supports exactly the functionality you are looking for, however I suppose you could select a random point and do a count of everything within range of that point.
I think that what you are talking could be quite a cpu intensive task (depending on how accurate you want it to be). Not something I would personally try and unload onto a portable device.