I have an interesting problem where I want to see if a pair of Latitude/Longitude points are within the region of 4 other specified ones. An application of this is specifying 4 intersections and seeing if the address is within that region. With the Google Maps Geocoding API (http://code.google.com/apis/maps/documentation/geocoding/) it's easy to convert the intersections into the long/lat and if the area is a perfect rectangle it's easy.... but what if the street is curvey? Does something like this already exist?
It sounds like you are looking for a point-in-polygon routine. http://en.wikipedia.org/wiki/Point_in_polygon
There are many implementations of point-in-polygon; if you are using PostGIS for your a database backend, use the ST_Intersects. There is already a question/answer on stackoverflow with code for a point-in-polygon function, see Point in Polygon Algorithm
Related
I'm trying to build a map with the following algorithm:
Wait for pan or zoom to occurs.
Query for all streets visible in the viewport (extent).
Color every visible street with a predefined color.
Example:
I want to show the numbers of businesses on each street, or the number of crimes committed at each street.
I have a DB which holds this kind of information (streetname, data), but each row doesn't have the location data.
Therefore, after each map zoom or pan, I cannot query all of it by a geographical bounding rectangle, it will be far more efficient to use Google own DB and query it by street names.
I know how to register to pan and zoom events.
I know how to calculate the viewport coordinates.
I know how to color a single street.
How can I get a list of all streets visible in the viewport?
Any other solutions or architectures are welcome.
The preferred solution will not use Google DirectionsService nor DirectionsRenderer since they slow down the map.
My understanding is that what you are asking is not possible from Google API's. Reverse geocoding inside a polygon is not a service they offer. There are some posts on other sites (e.g. https://gis.stackexchange.com/questions/22816/how-to-reverse-geocode-without-google) with the reference gisgraphy.com looking like a pretty neat reverse geocoding tool.
This still does not address your all streets in a polygon problem however. I think your only option would be to get your hands on the data (Open Street Maps) and write the code yourself. Further - if you are going to do this for a large area I would take an approach like I recommended here with grids: https://stackoverflow.com/a/18420564/1803682
I would create my grid elements, and for each street calculate all the grids to which it belongs and store in the database. Then when you search a polygon, you would calculate all the grids the polygon overlaps, and can then test the subset of road data in each of those squares to determine overlap.
I looked into this and abandoned a similar requirement a few months back and still have a desire to implement it. Most of the point/line in polygon work is happening on data created in my application (i.e. not street data) and right now that is the only data I will be including. What I am trying to say is - I hope someone gives you a better answer.
Update:
For what you are asking I still believe you will need to use a mix of your own database based on OpenStreetMap and some kind of grid analysis carried out in advance. If you have some time to commit to the project this should not be too awful to process. The database will be large, and the calculations needed will likely require a significant amount of one-time / upfront processing time. As far as highlighting routes/roads/whatever within the viewport, there are lots of way to accomplish this using the API - example here which I found useful: polyline snap to road using google maps api v3
Also useful: http://econym.org.uk/gmap/snap.htm
Note that one way streets may give some grief if using the directions api to snap to a street and you will likely have to watch for this and correct or reverse the start/end points.
Google would recommend using it's Geocoding Service in order to populate your data base with the co-ordinates. You can then use the LatLng Bounds Class method "contains" to check whether your points lie within the viewport. The advantage of this approach is you only need to geocode the information once and then store this, versus sending coding requests each time the viewport changes.
An alternate efficient way of displaying this kind of data may be to use google fusion tables. this greatly simplifies the integration of the data with the map.
I am trying to create an application that uses terrain information about an area. I use lon/lat (4326) polygons from a kml file and store the geometries in postgis.
I need to find the elevation fluctuations of a particular area (polygon) defined by lon/lat points. How is this possible? I have read certain possible solutions like DEM but i do not how to use them.
Is there any other way of achieving it?
Thanks in advance for your replies.
Surprisingly there is a Google Elevation API :) (mainly for Android development, you need to register for a proper key):
https://developers.google.com/maps/documentation/elevation/
Maybe you could use the JavaScript API of the same service (I haven't tried this one, just found the link from the previous one):
https://developers.google.com/maps/documentation/javascript/services#Elevation
Probably you can us it, but beware of this:
Use of the Google Elevation API is subject to a limit of 2,500 requests per day.
The good thing is that in one request you can get elevation data about a Line, with arbitrary number of divider points (the dividers are sectioning the line into equal length sections).
I would like to have the possibility to tell if a GPS location is in an inhabited or uninhabited zone.
I have tried some reverse geocoding services out there, but all of them proved useless, because they select the nearest address possible. (I understand why this should be so, it is useful for the purpose of reverse geocoding)
I have noticed in Google Maps, when I search for a city, their boundaries are selected in red dotted well defined line. I would love it to use this, or something similar.
Is there any possible way that Google maps can provide such a service, or something that can solve my problem.
Are there any other web solution or databases that you know of that can give me this information ?
Or maybe I can use any of the reverse geocoding solutions with some parameters (such as restricting the size of searching) to determine if the location is or is not in a populated area?
If you will not find a public service then it gets interesting, and expensive in terms of developping effort.
Public data (world wide) is only available from OpenStreetMap, i think they have such a layer (could be named Land_use (rural, etc.)) This layer is usually used to color a map, look at openstreet map Web page if you find a suitable coloring, that coresponds to your task. (E.g look at green, or gray).
These data are stored in polygons, you would have top extract these polygons (i asume millions of them). Ten you need a fast searching spatial index, like a region Quadtree.
Then you do a "point(lat, lon) in polygon" call, and get the polygon related to your position.
Probaly not all that polygons will fit into main memory, so you must load them on demand (e.g by country).
A variant of this approach is to use a geo spatial database like postgres to store that polygons, and do a DB query.
With that approach most work will be extracting the polygons from OpenStreetMap DB file.
More acurate is data from TomTom, but these can be really expensive.
Trouble!
I'm looking for a way to find the countries within a given range of LAT/LONG coordinates.
E.g.:
When viewing an area in Africa using Google Maps, I get out which countries that are in my current view.
This is a bit ambitious, and I think the main problem will be dealing with accuracy of the needed polygons. The accuracy of these don't need to be all that great, the borders can probably be tens of miles off, or even more.
This will be needed for the entire world.
You can solve this easily using QGIS based on the assumption that you have
A GIS layer of Africa (if not you can find one using google
A point layer based on Lat long (or you can use Qgis's text delimited import)
using ftools -or- Vector menu, there is a feature called points in polygons that should solve your problem
You can try using the Yahoo WOE ID stuff... Here is a great article on it:
Yahoo Woe. Flickr has a similar service (I think it uses the Yahoo one under it...): Flickr
If I had lat/long data for all our leads in Salesforce, is there a way to write a query to group them, or say list all the leads within 10 miles of San Francisco, CA ?
[EDIT: Clarification]
I have thousands of leads with both a full address, and long/lats.
I want to build a query on these leads that will give me all of the leads near San Francisco, CA. This means doing GIS type work within salesforce.
I could of course filter specifically on city, or zipcodes or area code, but this presents some problems when trying to rollup a whole metro area.
Yes. You need to Reverse GeoCode them with a tool/service. In the past I have used Maporamas service but it was quite expensive and that was before Google maps and virtual earth existed so I am sure there is something cheaper(free) out there now.... Googling around I have found this and this
EDIT:
OK from What I understand you are trying to calculate the distance between 2 lat/long points. I would start by discounting the ones that where outside you sphere of (lets say) 10 miles. So from your central point you will want to get the the coordinates 10 miles, East, West, South and North. To do this you need to use the Great-circle distance formula.
From that point you have you Sales Force Data if you wish to break this data up further then you need to order the points by distance from the central point. To do this you need to use the Haversine formula
I am not sure what you language preference is so I just included some examples from SQL(mainly) and C#
Haversine Formula in C# and in SQL
Determine the distance between ZIP codes using C#
Great Circle SQL
Great Circle 2
Use GeoHash.org (either as a web service or implement the algorithm). It hashes your lat-long coords into a form that appears similar for nearby places. For example A may have a hash like "akusDf3af" and B might have a hash like "akusDf3b2" if they are nearby. Then do a SOQL query that looks for places starting with the same n characters as a known location. Your n will determine the radius of the lookup.
These are some great technical solutions that can provide very exact answers, but two things to consider:
geospatial proximity does not map neatly to responsibility
Ownership calculation seems to be done best through postal code lookups or other rules that don't allow for gaps or overlaps. Otherwise, you'll have two (or more) salespeople fighting over leads that are close to both of them, and ignore those leads that are far away from both of them.
So, if you're using geo-calculations like those above to assign ownership, just acknowledge the system will leak and create business rules to accomodate for that. But a simple postal lookup to define territories (as salesforce's own territory management feature does) might be better.
I'd suggest the problem we're trying to solve geospatially is not who owns which lead. Rather, given all the leads you own, which are nearby?
maps often offer more data per pixel than columnar reports
Again, geospatial data in a report may not be the best answer. A lead 50km away, but along a major road, is more interesting than another lead 50km away on the other side of a mountain or lake. Or a lead close to other leads is more interesting than a lead by itself.
A report can't show this, but a map can.
Salesforce has some great examples of Google Maps integrations. Instead of a columnar report called "My Nearby Leads", why not a visualforce page, with a google map inside? You're giving the user far more information than a columnar report could. They might like it better, and it's easier to implement than trying to calculate some of the equations above.
Just another perspective that may (or may not) be appropriate to the problem at hand.
This post is really old, but is showing up at the top of Google results, so I figured I would post some info to it anyways.
2 nice mapping tools are batchgeo.com and geocod.io. Geocod.io can even give you lat and long coordinates from an address.
If you just need a one time calculation, you can use Excel. Export all your leads with the lat and long. Then go to Google Maps and get the lat and long in decimal degrees for the city center of wherever you want to measure to.
Then use this formula in excel to calculate the distance between the coordinates in miles. Lat1dd and Long1dd are the coordinates for one point, and the lat2dd and long2dd are coordinate points for the other point.
=3963*ACOS(COS(RADIANS(90-lat1dd))*COS(RADIANS(90-lat2dd))+SIN(RADIANS(90-lat1dd))*SIN(RADIANS(90-lat2dd))*COS(RADIANS(long1dd-long2dd)))
After you run it, just sort the results from smallest to largest to get those results that are the closest.
I haven't done this next part yet, but conceptually it should work. We have a field that lists the major market each account is in. Example, Chicago IL. I am going to build a trigger or formula field that essentially says IF(Market="Chicago IL") then use X and Y for the lat and long. These will be hardcoded as the city center for that specific market. The query will then run each individual account's lat and long against the one from the city center to calculate a distance.
If you wanted to break the market into different zones, you could adjust your formula so it uses < and > on the lat and long fields. Everything less than X but greater than Y goes in Zone A, etc.
Hope this helps someone.