On 12 May 2011 21:41, Ben Appleton <apple...@google.com> wrote: > > On May 13, 2011 2:37 AM, "Richard Quadling" <rquadl...@gmail.com> wrote: >> >> On 12 May 2011 14:12, Ben Appleton <apple...@google.com> wrote: >> > It sounds like you have a polygon containment forest: a collection of >> > rooted >> > trees whose roots are outer polygons, children are polygonal holes, >> > grand-children are polygonal islands inside holes, etc. You can >> > certainly >> > represent containment in JavaScript, but it's not necessary for >> > rendering. >> > Therefore the Google Maps API does not represent containment. >> > >> > There is an unfortunate caveat. Many browsers use Canvas to render >> > vector >> > graphics, and Canvas requires that outer vs inner polygons have opposite >> > orientations - it implements only "zero-winding fill". For example, if >> > your >> > outer boundary is clockwise, your holes must be counter-clockwise, >> > islands >> > within holes must be clockwise, and so on. If you need to determine the >> > orientation of a polygon you can use the geometry library's >> > computeSignedArea method >> > >> > (http://code.google.com/apis/maps/documentation/javascript/reference.html#spherical). >> > You can then traverse your containment tree to ensure that outer vs >> > inner >> > polygons have opposite sign, reversing polygonal loops to negate their >> > sign >> > where necessary. >> > >> > Incidentally the geometry library also has a method to encode >> > polylines/polygons in the same format as you reference, but compiled so >> > it >> > loads faster. >> > >> > So I suggest: use google.maps.Polygon to visualize your polygons, but >> > wrap >> > it in another class or datastructure to represent your containment >> > forest. >> > To visualize simply add the google.maps.Polygon to the map. When >> > constructing queries to your server, consult your wrapper class / >> > datastructure to determine which polygonal loops are outside vs inside. >> > Optionally, also switch to using the compiled poly encoder in the >> > geometry >> > library. >> > >> > Hope that helps >> > Ben >> > >> >> Thanks for that. >> >> encodePath only allows for a single path, not a set of paths. I'm >> simply concatenating them with | (pipe). And splitting and decoding >> them in PHP. How do I access the compiled encoder. I'm currently >> using google.maps.geometry.encoding.encodePath() > > Oh great, you're already using it. I thought you meant you were using an > older JavaScript poly encoder that had not been compiled. > >> Very useful. -ve values from computeSignedArea() relate to the outer >> polygons and +ve values to the inner ones. > > That's right. > >> I think the final piece for me now is to determine from 2 polygons if >> one is completely within the other. > > I thought you already had this structure. Else, how are you currently > generating KML and WKT queries as you mention? > > Cheers > Ben >
I'm still in building/designing/learning/playing phase of the development. Essentially proving to myself and the team that what we want to do is possible. I'm working things out manually. In the last test (test 5) I create a map, added a simple polygon and send the encoded path to PHP to decode and turn into WTK for SQL to get the pins to pass back to the map for displaying. For a single polygon (I've used 2 sliders to allow different number of points and radius) this is working fine. I have to use a polygon as whilst I'm only playing with regular ones, the final view of the app will be to have complex boundaries. The next test was to add the exclusion polygon. That's where I'm at now. Though I'm still playing I know that the users will need to be able to define these complex areas. The purpose of the tool is to allow our call centre staff to display the location of a LGV (Large Goods Vehicle) breakdown and, based upon the contract (essentially who owns or is hiring the vehicle) provide a ranking of the most appropriate maintenance engineers, nearest to the breakdown. We have nearly 1,000 service depots in the UK. Each depot covers an area. Sometimes just as a 30 mile radius, others cover a specific county, or part of it. Others don't go inside a circular motorway/ring road, etc. All different. Some will travel over bridges/ferries/etc. Or have any sort of boundary/exclusion. The next step in the design is to allow a backoffice user the ability to plot out these boundaries. The boundaries will be stored in our SQL Server in 2 ways: 1 - Using the Google Maps encoded form, so when I need to display the polygon, I can just supply that to the client app, call the decoder and add each path to the polygon. 2 - As a SQL Server Geography type, so I can use SQL Server to do all the intersection and find a list of service providers who cover the point of the breakdown and are attributable to the contract for the vehicle. Obviously, there is more to the front end than just the map, but the map is one of the key players. The map will also show any service provider that has part of their boundary within the viewport, so, if the preferred providers are unable to handle the breakdown (some providers are quite small and only have 2 or 3 maintenance staff), the user can see that there are other providers in the area who are linked to the contract and may be able to help, even though it is outside of their boundary. It's all very fluid, but not a total free for all. Travelling time for the maintenance people means some driver is sitting in their cab waiting and having the stock not being delivered. The vast majority of the contracts are delivering perishables and delivery times are quite tight. And I then, on top of all of this, ... GoogleMaps ... LatLng(latitude, longiture) Polygon orientation of points to create a small closed area : clockwise WTK (as used by SQL Server) POINT(Longitude, Latitude) <<< Reverse POLYGON orientation of points to create a small closed area : anticlockwise. Otherwise the enclosed area encompasses the whole of the earth, except the small part "outside" the boundary. And to this, the MS SQL native Geography::Point() method uses Point(latitude, longitude), the reverse of WTK but matches Google Maps API. Don't you just love standards! -- Richard Quadling Twitter : EE : Zend @RQuadling : e-e.com/M_248814.html : bit.ly/9O8vFY -- You received this message because you are subscribed to the Google Groups "Google Maps JavaScript API v3" group. To post to this group, send email to google-maps-js-api-v3@googlegroups.com. To unsubscribe from this group, send email to google-maps-js-api-v3+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-maps-js-api-v3?hl=en.
