i am facing this problem : I have in my database some vector data (polylines ...) which describe many world/country/region/cities boundaries.
I would like to have an interactive map on thoses areas.
When i render those data in the browser (data are sent in geojson) this is slow (i'am not surprised).
The next reason, is to generate some raster tiles to represent the areas at different zoom level and to have a way to make the relation between a click on a area and the area selected (to display more info).
I am a newbie in geo tiles :
What is the best tool to generate png/jpg tiles from vector data?
How to make relation between an area clicked and a "id" in database?
I know my questions are very large, but if you have some advices ...
Thanks!
I recently wrote a blog posting on how to improve the rendering speed of raster tiles:
http://blog.webfoot.com/2013/03/12/optimizing-map-tile-generation/
As for connecting a click to a jurisdiction ID, I don't think there is a shortcut: you need to translate the click into lat/lng (or Vast Coordinate System, as I describe in the blog post) and then do a point-in-polygon check. If you are using PostGIS, then you can do an ST_Intersects.
NOTE: if you are using MySQL, the intersection is done with bounding boxes, not the polygons. It still is possible: you just need to grab a point-in-polygon function from somewhere to check which polygon if a bounding-box check gets you more than one.
Here is an example of dots you can click on:
http://maps.webfoot.com/demos/CanadianStimulus/CanadianStimulus.html
Note that because people aren't precise with clicking (especially with tiny dots), I actually make a few pixels around the dots "live" as well as the single-pixel dots. You can also click away from the dot, and then it will show the polygon (which in this example's case, is the federal electoral district).
There is a MongoDB Plugin datasource for Geoserver, a full featured WebGIS Server. You can use it to build up a map rendering service (a WMS actually) ofyour data. Then use Geowebcache to generate tiles of your map.
This way you can use fully featured WebGIS stack, which allows you to manage additional datasources, and easy tile subset recreation if portions of your data get updated.
Also querying features on a map (relation map position to element in database) is provided through Geoservers WFS implementation.
Related
I am creating a game in flutter in which I want to create my leader board page in which I want to achieve the list like Reorderable widget but in that we drag the tile manually but I need to get it automate ,it should elevate and lower another tiles same animation like Reorderable list but it should be automated
I hope I will find some solution with large community
You can take a look at the AnimatedList in Flutter: https://api.flutter.dev/flutter/widgets/AnimatedList-class.html
When a new value is inserted (or removed), it is automatically animated (and you can of course customize this animation to suit your needs).
I'm not sure how you would handle moving an item from one place to the next in the list, though.
Update
I found this other SO thread which mentions the great_list_view package, in which you can just update your underlying list (with the new score, or sort it again) and it will automatically animate it for you. That sounds like a good option, and the package has recently been updated and has a decent amount of likes on pub.
https://pub.dev/packages/great_list_view
I have a set of pixel perfect icons which I want to use on toolbar (NSToolbar) of my app. Toolbar is configurable thus I need to provide icons in four sizes: small, standard, small#2x, standard#2x.
I could not find any official information about the size of those icons, but unofficial information (confirmed by my tests) is the following:
small is 24px, normal is 32px.
Thus I need to add four different images: 24x24px, 32x32px, 48x48px, 64x64px to my image set.
As for now I could not find a correct way for that.
I have tried a dozen of different methods but could not find one which preserves pixel perfect quality of all four images.
I believe, I can load right size of the image manually each time it has to be changed, but I am wondering if where is a correct way for that.
Does anyone has a good solution for that?
And yes, I clean build folder before each test.
See the Apple Developer site Human Interface guidelines for formats and sizes. The requirements are different for the different devices, and quite detailed.
For a quick & dirty solution if you're not ready to ship and just want nice looking graphics for testing, I've found that one 512 x 512 pdf, labeled "image#2x" works pretty well. You need to set the
imageScaling = .scaleProportionallyDown
and Cocoa will take care of the rest. But it's definitely not ready for prime-time.
The NSToolbar.sizeModes are enum: small and regular. Small is 24x24 and regular is 32x32; additionally the retina options allow for #2x (48x48 and 64x64) and potentially #3x future-forward.
Apple documentation on these sizes can be found here and here
Make sure to use enum Regular not "Standard", which is undocumented.
There are several examples in the API, but for some reason, what I think the biggest feature is eluding me for some reason. I have a list of points and each point needs to be represented by a different icon. I also may have layers that use the same icon which I can find, just not the option for different icons/markers. An example of this would be greatly appreciated!!
I found out how to use the Graphic option to add an array of points that have a different url for their markers (symbols). This used the Picture Marker type. The beauty of JSON!!
I'm currently creating a new website based on geo-localised information to display on a map. I've never done this kind of development before, and my researches don't lead me to a decent result.
What I want to do is load a few POI on the map, say 15 by 15 until all POI are loaded on the map (This is to show the user that data is loading progressively).
I know how to load said POI 15 by 15 based on their update date in a scrollable list (Using limit and offset, but this implies that we have the same reference as a starting point), and now I want the same kind of behaviour, but based on their location instead of the timestamp.
What I'd like to do is trigger the update based on the center of the map when it moves, so that it starts loading POI in the displayed area, but without reloading what was already loaded.
I can't figure out how to do that.
Say the user moves the map to the side, but keeps some POI on the map, it should reload from the center to the edge of the map without re-adding the POI.
Also, when the user zooms out, it should load around the already present POI, as the center was already loaded on previous zoom.
The only think I was able to find and understand is how to sort POI based on a distance, with the Haversine formula from here:
http://www.plumislandmedia.net/mysql/haversine-mysql-nearest-loc/
But it doesn't cover the part where you interact with the map and need to load new data to add it to what's already there.
I'm using Leaflet to show information on the map and listen to events.
Any guidance welcome.
I would like to replicate the song view of the Music app, in my Windows 8 Metro app using WinJS.
I'm using a StorageDataSource to load files from the music library in a list view. This works well, now I'd like to group music files by some property (ex.: album).
StorageDataSource does not support grouping, so I'm looking for tips on how to go at this. It has to be efficient as the user can have many items in the library, but I don't need it to auto-update when new files are added/removed (though it would be nice).
My current understanding is that I need to build 2 custom data sources:
One or the itemDataSource of the ListView, and is a wrapper around StorageDataSource. Ex.: the getItemsFromIndex implementation queries the underlying dataSource for its items that it wraps in a literal. I can't just set the StorageDataSource as its objects are immutable.
One for the groupDataSource of the listView. I build it manually once when the app loads, by iterating over my first StorageDataSource and determining how many groups I have, and where each one starts in terms of itemDataSource indexes.
It works, but I wonder if there's a better way. It also seems impossible to have groups in a ListLayout and it forces items to be displayed horizontally.
Does anyone have tips for the high level view of what's required here? Thanks.
First, you are correct that if you are using a list layout that grouping isn't supported; its only supported in the Grid layout. You could choose to insert fake data items for the groups that you could style as you needed using a custom item template rendering function.
The rest of your stuff will require some learning I suggest you take a look at the ListView samples to really understand the ins and outs of the data source API.
One option is to let the ListView calculate them for you by supplying the computerDataSourceGroups function:
http://msdn.microsoft.com/en-us/library/windows/apps/hh700578.aspx
The other option is that the StorageDataSource source is right the for you to look at; adding grouping to this as a raw datasource may in fact be your most efficient and maintainable solution. It will hopefully allow you to continue to leverage the virtualization of the listview without causing the data source to de virtualized. You should find the source in the references node in VS, in ui.js.