I'm writing a web application using the google maps api v3, which displays places of interest for my customers. These won't be places which appear on google maps, and I want users to be able to filter the results to match their specific needs.
I've got it working so that the map centres on the user's current location on load. However, it does allow them to type in another address if they wish. When I do this, the map default to results in the American region.
Is there any way to get the region parameter for the map from the user's current location and use this to get more relevant results?
Another function I would like to implement is searching only for results within a certain (user-specifiable) distance from the given location. Currently all the places are stored in a MySQL database (with their address, latitude and longitude) and I iterate through all places and use this formula to determine the distance. I anticipate that I might get 50,000 places in the database.
Should I be worried about response time for this calculation, and is there a way I can make it quicker? Is having my data stored in a MySQL database a good idea in general for this kind of application?
Biasing geocoder results:
To bias the geocoder results, you can use navigator.language as the region parameter. It should provide more relevant results to the user.
Other way to improve the results might be by using the user's current location. You can use viewport biasing to improve the results (you can calculate some bounding box around the user's current location).
Using user's current location to acquire value for the region parameter is problematic. I'm not aware if there is some public API to acquire IANA language subtag from a location. But you can use the reverse geocoder to translate the location, then extract a country code from the results. The problem is that some country codes doesn't match the IANA language subtags that are required (e.g. ca is the country code for Canada but language subtag for Catalan, Valencian). However most of the time using the country code instead of language subtag should improve the results.
Storing latlng in MySQL db:
I'm afraid that iteration through all places and applying the Haversine formula might be very time consuming (some study about it here).
Probably the best way to handle laglng data in MySQL is to use spatial extensions. A nice blog post about using it.
Related
I am developing a Map based iOS app in Objective C. Basically what I need to achieve is to get the details data of suggested location that is within 5 kilo meter to the current user location without using Google API. I have searched a lot but could not find any answer to my question.
I tried below links related to my problem but could not get satisfactory solution :
how to find nearest latitude and longitude form current place?
get nearest locations from my current location
http://api.geonames.org/findNearbyPlaceNameJSON?lat=12.9972&lng=77.6143&radius=5&username=demo
How to get the nearest area from a list of locations?
I want to know if there is some other good and efficient approach (free).
Thank You !
If you have the coordinates of all the places you want to search from in database, then you can implement Haversine formula in sql query and this will return results within the specified distance as in your case 2km.Refer to this link for detailed information.
There are lots of existing questions relating to this issue, but I have looked at as many of them as I could find and did not get an answer.
I'm trying to perform an offline reverse geocoding lookup on iOS based on a latitude and longitude. I'd like to be able to provide a latitude and longitude, and be provided with the country in which that point lies. I can do this with Geonames (such as: http://api.geonames.org/countryCode?lat=45.03&lng=8.2&username=demo), but I need a similar ability offline, without Internet functionality on the device.
CLLocation does not provide offline services that work reliably enough for what I'm doing, it relies on caches made while you were previously online, etc. Messy.
I've tried this: https://github.com/drodriguez/reversegeocoding but haven't had any luck, it requires some slightly complex / confusing Terminal installations using something called Thor which I've never heard of, and was throwing up a variety of errors, so I bailed on it.
I've found a few downloadable maps, but these seem to be even more complicated, and worryingly, hundreds of megabytes or even gigabytes in size – much beyond the scope of an iOS app. I only need countries, nothing smaller than that (cities, streets, locations, etc.) so I think I should be able to get a much smaller file.
So my key question is: is there some pre-existing database or tool, preferably with iOS support, that I can feed a latitude/longitude, and get a country? And, if not, what steps should I take to get such functionality working on my own?
Thanks in advance.
ReverseGeocodeCountry is a simple lightweight offline country reverse geocoder for iOS, it has a static JSON file with country polygon data that is used to reverse geocode any lat/lng:
https://github.com/krisrak/ios-offline-reverse-geocode-country
The "Countries of the World" is a .csv text file with countries, coordinates, localised country names, capitals and other information. It seems to be free to use. You just have to import it into an SQLite database.
Edit Just noticed you want reverse geocoding. The database would only be good for forward geocoding.
You can download shapefiles for all countries at http://www.gadm.org/download. If you download a .kmz, you can unpack it to a list of coordinates for the borders. You could probably take every 5th or 10th coordinate to get smaller size (with less accuracy).
Just in case I can suggest another good written offline geocoding library.
https://github.com/Alterplay/APOfflineReverseGeocoding
In my app I have a lot of data about a great number of places (e.g. restaurant, museum, etc...) but I haven't coordinate but only address or zip code;
I want to know if address or zip code is possible obtain coordinate for all of my data. I know that I can do it with reverse geocoder but I have a large amount of data; I know that google don't allow make many many request...is there another solution?
Thanks.
You could write a simple webpage with a javascript that uses Google's API. It would send the address/zip code to Google's geocoder and print the results into a textfield to get their coordinates.
I'm working on an iOS app that pulls events from Google Calendar and subsequently generates pins on a map for each event (based on what the event creator fills in for "Location"). The user can select a date range (today, this week, this month, etc.) and see all the events taking place near them over that period.
Problem 1: The app is for my local university, so a majority of the locations will be buildings on campus. These buildings have inconsistent addresses that are often difficult to find, so it would be good if the location "Foo Hall" would result in a pin on that building. Google Maps is capable of doing this, however Apple Maps has no knowledge of the buildings on my school campus.
Problem 2: In an ideal situation, thousands of students would be using this app. Each time they open the app, they could be viewing dozens of pins. Therefore, I'm worried that I may be pushing the limits imposed by Google's geocoding API (definitely the 2500 request limit, and maybe even the 100,000 request limit for the Business API).
So my question is... what would be the best solution for these two problems? Should I create a local database for building names and map them to coordinates? Or is there a way I can overcome the limitations of Google's Geocoding API? Is there a better solution I'm not thinking of?
Thanks for any help!
I would use latitude and longitude coordinates for the buildings and allow for people to add locations to the database if they are meeting somewhere that you have not added already. This way, the pins will drop in the center of the building if you want them to, because you are not relying on an address or on looking up a building name. You simply know that "Foo Hall" is at X latt. and Y long. And if someone selects "Foo Hall" or sees an event at "Foo Hall" there is a perfectly placed pin right in the middle of it on the map. I don't think you need to worry as much about the geocoding API if you are using hardcoded locations for the buildings either, because you won't have to be polling Google to get the building locations.
I would also use some sort of server to store the building locations so they can be updated or added to, either by you or by the users.
That's how I would handle it, good luck!
Given a latitude and longitude, what is the easiest way to find the name of the city and the US zip code of that location.
(This is similar to https://stackoverflow.com/questions/23572/latitude-longitude-database, except I want to convert in the opposite direction.)
Related question: Get street address at lat/long pair
Any of the online services mentioned and their competitors offer "reverse geocoding" which does what you ask--convert lon/lat coordinates into a street address of some-sort.
If you only need the zip codes and/or cities, then I would obtain the Zip Code database and urban area database from the US Census Bureau which is FREE (paid for by your tax dollars). http://www.census.gov/geo/www/cob/zt_metadata.html.
From there, you can either come up with your own search algorithm for the spatial data or make use of one of a spatial databases such as Microsoft SQL Server, PostGIS, Oracle Spatial, ArcSDE, etc.
Update: The 2010 Census data can be found at:
http://www2.census.gov/census_2010/
This is the web service to call.
http://developer.yahoo.com/search/local/V2/localSearch.html
This site has ok web services, but not exactly what you're asking for here.
http://www.usps.com/webtools/
You have two main options:
Use a Reverse Geocoding Service
Google's can only be used in conjunction with an embedded Google Map on the same page, so I don't recommend it unless that is what you are doing.
Yahoo has a good one, see http://developer.yahoo.com/search/local/V3/localSearch.html
I've not used OpenStreetMap's. Their maps look very detailed and thorough, and are always getting better, but I'd be worried about latency and reliability, and whether their address data is complete (address data is not directly visible on a map, and OpenStreetMap is primarily an interactive map).
Use a Map of the ZIP Codes
The US Census publishes a map of US ZIP codes here. They build this from their smallest statistical unit, a Census Block, which corresponds to a city block in most cases. For each block, they find what ZIP code is most common on that block (most blocks have only one ZIP code, but blocks near the border between ZIP codes might have more than one). They then aggregate all the blocks with a given ZIP code into a single area called a Zip Code Tabulation Area. They publish a map of those areas in ESRI shapefile format.
I know about this because I wrote a Java Library and web service that (among other things) uses this map to return the ZIP code for a given latitude and longitude. It is a commercial product, so it won't be for everyone, but it is fast, easy to use, and solves this specific problem without an API. You can read about this product here:
http://askgeo.com/database/UsZcta2010
And about all of your geographic offerings here:
http://askgeo.com
Unlike reverse geocoding solutions, which are only available as Web APIs because running your own service would be extremely difficult, you can run this library on your own server and not depend on an external resource.
If you call volume to the service gets up too high, you should definitely consider getting your own set of postal data. In most cases, that will provide all of the information that you need, and there are plenty of db tools for indexing location data (i.e. PostGIS for PostgreSQL).
You can buy a fairly inexpensive subscription to zipcodes with lat and long info here: http://www.zipcodedownload.com/
Or google's reverse geocoding
link
http://maps.google.com/maps/geo?output=xml&q={0},{1}&key={2}&sensor=true&oe=utf8
where 0 is latitude 1 is longitude
geonames has an extensive set of ws that can handle this (among others):
http://www.geonames.org/export/web-services.html#findNearbyPostalCodes
http://www.geonames.org/export/web-services.html#findNearbyPlaceName
Another reverse geocoding provider that hasn't been listed here yet is OpenStreetMap: you can use their Nominatim search service.
OSM has the (potentially?) added bonus of being entirely user editable (wiki-like) and thus having a very liberal licencing scheme of all this data. Think of this of open source map data.