I'm using Graphhopper as a routing service for my Android project and I want to know how can I extract street data (as a polygon) from *.osm.pbf format?
Later I want to use that data so that I could detect if user is within boundaries of that street.
Edit:
I've used Osmosis as it was referenced in this answer (selecting highways) but when I try to investigate xml after extraction I still don't understand how can I get a particular street since there still are some other objects left (like houses, bus stops).
Well I guess here are a few misunderstandings, so I go trough your wishes step by step:
OSM street data
What grasshopper uses aren't street polygones (closed shapes) nor simple street lineshapes. It processes pure OSM data and creates a so called routing-graph presentation. Here are a few informations about the import process itself: https://github.com/graphhopper/graphhopper/wiki/World-Wide-Road-Network
User position on road
This is called reverse geocoding and has different requirements on the indexing structures and models. OSM offers Nominatim as a solution to query like (lat, lon) -> OSM object. Your idea with a spatial buffer is even possible but creates a lot of overhead (here: memory) to preprocess your roadnetwork or doing it on demand for a particular area.
Street data is stored in GraphHopper. You could traverse the full graph e.g. via extending XFirstSearch and then do on checkAdjacent:
boolean checkAdjacent( EdgeIterator iter ) {
PointList pl = iter.fetchGeometry(3);
String name = iter.getName();
}
If you want to get an edge from a location for the "fence-use-case" you can have a look into LocationIndexTree.
Some clarifications:
Routing graphs usually don't contain spatial informations
The routing graph itself does not need this data but still we need this data to display the route etc.
Is there a way then to add weight to a node during the calculation
As explained on the mailing list.
Related
I am working on an app that have over 2 millions of user. It is going to introduce location based feature. From the very beginning we want to provide the user a location based notification which will be changed based on their location/region. I am using PostGIS and Mapbox technologies. I have a custom polygon which is the indicator of different region. I know I can use a ST_Within of PostGIS to get the polygon info by sending longitude and latitude to server everytime. I am using the folloing function to get the region
CREATE OR REPLACE FUNCTION getRegion(getlng numeric, getlat numeric, OUT outregion text)
as $$
BEGIN
SELECT region into outregion
FROM mypolygon
WHERE ST_Within(
ST_GeometryFromText(
'POINT('|| getlng ||' '|| getlat ||')', 4326
),
geom);
END; $$
LANGUAGE PLPGSQL;
and calling the function by
SELECT getRegion(getlng, getlat);
But as there are millions of user it will increase the load on database server and need to be increased the TPS. Is there any other way to get the polygon/region from point beside using postgis directly? The region polygon is changable, not constant.
There is a method called ray-casting and recently mapbox is supporting query withing vector tiles. Is ray-casting or query within vector tiles will be a better approach for doing the same thing? (Again remember, the polygon is not constant.)
In a nutshell, I actually want to know the best practices using currently by the community to reduce the load on server and save time.
1) You will have to index your polygons using some grid (may be UTM, Google tiles or your own custom grid)
2) Identify grid of user location
3) Now fetch the polygons which lie on the same grid .In the best case you will get only single polygon and you will not have to use ST_Within.
4) Now if you get multiple polygons use ST_Within with only these polygons instead of the entire list of polygons
This Algo will save lot of memory and processing as ST_Within is a very heavy process.
Note: I have been using this approach from past 4 years and it has done wonders in terms of time and memory saving
I have an ever increasing list of places identified by lat/long stored in my database. Now at the UI front there is a screen with a place auto-complete textbox means if I type a location there a drop down will appear with places and when I select the place the camera will move there. Also it is required that I display locations nearby (locations as stored in my database). Now the question is how to do this? I can use
SphericalUtil.computeDistanceBetween()
But the problem is I can't fetch all lat/long from my database and calculate distance without hampering performance.
You would need to compute the distances in your database. There are two basic options:
Implement your own distance method in your database:
If your positions are close to each other and close to the test lat/lng you can use Pythagoras's theorem (a ver basic approach that will not be correct in all the cases)
To address all the possible cases you can implement yor own haversine formula (the haversine formula gives great-circle distances between two points on a sphere from their longitudes and latitudes and is used to compute distances in the SphericalUtil.computeDistanceBetween() method).
Use a GIS database. You can use SpatiaLite for Android and use the ST_Distance function to filter your positions:
SELECT *
FROM yourtable
WHERE ST_DISTANCE(Geometry, MakePoint(yourXcoordinate, yourYcoordinate)) < yourdistance
I have an question that while using Google Direction Api we can get the list of data like city's name, its Lat & Lng etc but the data provided by Api is limited to some extend. It's not able to provide all cities coming with-in that particular route.
E.g. If we try to go for Chandigarh to Delhi, then the route has a fixed result but when we try to reverse that same search i.e. Delhi to Chandigarh, some of the cities coming in previous result get vanished in api's new result, moreover, we just have a limited amount of locations/cities in result while we need the route completely detailed.
Do any of you guys faced this issue before? Is there any other way to match such requirement?
Hope I am understandable.
Thanks.
Use the below url:
https://maps.googleapis.com/maps/api/directions/json?origin="latvalue","longvalue"&destination="destnLat","destnLong"
&sensor=false&avoid=highways&mode=driving&alternatives=true
you have to set the alternatives value to true so it will result different routes available between the source and destination
According to various references, Google Maps has a query param called sll which does the following:
Latitude,longitude of the point from which the business search
should be performed. You could use this to perform an off-centre
busness search. Google use it so "link to this page" can record a map
that has had the centre moved after performing a business search. When
requesting a route
map.getBounds().getSouthWest().toUrlValue() returns the
same value maps.google.com uses.
So, for instance, if (43.464258, -80.52041) happens to be in Waterloo, Ontario, and (42.24370, -82.98320) happens to be in Windsor, Ontario (many hundreds of kilometers away), then my interpretation of the above documentation would be that the following query:
https://maps.google.ca/maps?saddr=43.464258,-80.52041&daddr=mcdonalds&sll=42.24370,-82.98320
will do a search for "Mcdonalds" from Waterloo, to some McDonald's in Windsor.
Unfortunately, that's not what happens (click for yourself to see!). It ends up doing a search from the saddr point, to the nearest McDonald's to that point. The value of sll doesn't factor into it at all.
But here's where it gets weird! If I omit the sll parameter entirely, then Maps does something completely unexpected: it picks some random McDonald's in Toronto (a city that is many kilometers away from either Waterloo or Windsor). I need to add some sll parameter (for any value) to make Maps return a result in Waterloo (even though what I'm asking for is a result in Windsor).
Am I misinterpreting all the various sources of documentation about this parameter? Is this a bug on Maps' end? And, most importantly, is there any working way to do what I'm trying to do, even if it doesn't involve the sll parameter at all?
I can get it to work with a simple query :
from:43.464258,-80.52041 to:mcdonalds near 42.24370,-82.98320
Which gives the expected result. It won't work without near which is a keyword.
You can also search from:43.464258,-80.52041 to:mcdonalds, Windsor if you have the city name.
About the sll (and sspn) parameters, it doesn't work for directions AFAIK. It only works with searches for a single location.
I am able to prepare route between two points. Now i want that in addition if i want to travel via a different point in between my route, what approach i should take.
I finally got it. Analyze this Url :
Long Route:
http://maps.google.com/maps?f=d&source=s_d&saddr=46.871716,2.361546&daddr=47.871716,2.361546+to:49.871716,2.361546
where :
saddr is the starting address
daddr is the midpoint
to: is the final destination
What you should be using is
http://maps.google.com/maps?f=d&source=s_d&saddr=46.871716,2.361546&daddr=47.871716,2.361546+to:49.871716,2.361546&sll=46.871716,2.361546&dirflg=w&hl=en&ie=UTF8&z=14&output=kml
where :
sll is the starting address
output gives you a kml output data
You can parse this output kml using a SAX parser to get the series of lat,lon addresses seperated by spaces with the shortest path to your destination, including your midpoint.
How you prepare your route? I'm for this purpose use Google Web Service, you pass link to service and get *.kml file from it. This file contains points of your route wich you can draw on MapView. See example here and descriptions of various parameters here