i need a help
i have a shape file that continue 3716 polygon record and want to draw this shape file where some of those polygons need to have a specified color
OR WANT a search technique to search this map for a point (lat-long) and get it's belong polygon but not by searching all polygons
i tries all, OpenJump-Source code, GeoTools,....
In GeoTools you can follow the Style tutorial to show you how to display your shapefile. There is no way to carry out a point in polygon search without at least examining the bounding box of each polygon but the GeoTools Query Lab will talk you through the basics of setting up a query (and if your shapefile has a spatial index then it will be quick enough).
Related
I'd like a user to be able to draw a polygon using the Azure Maps Drawing Manager and have the ability to move a point of the polygon to near one of another polygon's points and have the dragged point snap to the same location such that the resulting 2 points would be the same.
I know there is snap capability with a grid but don't see a sample for this behaviour?
The ultimate goal is to prevent polygon overlaps, assuming the intersecting shared line of adjoining shapes is excluded from determination of which polygon a point resides within.
I can allow a user to manually draw and get as close as possible of course, and provide some assertion to confirm no polygons overlap but would additionally like a nice snap-to-point experience if possible.
You can find hundreds of samples for Azure Maps here: https://samples.azuremaps.com/
As you noted, the snapping grid is likely the best place to start in your scenario. Here are some specific samples of this:
https://samples.azuremaps.com/?sample=use-a-snapping-grid
https://samples.azuremaps.com/?sample=snap-grid-options
The following sample is an example of a custom snapping scenario where the routing service is used to snap a drawn line to a route (the route part can be swapped out for custom logic): https://samples.azuremaps.com/?sample=snap-drawn-line-to-roads
I am trying to draw a polygon with maps drawing tool. Now I want to store useful information about that polygon in the database so I can again draw that same polygon by retrieving the data.
what is that information and how I can use that to draw same polygon?
I would suggest you use a Data type of Varchar/ Specific data type (depending of Database in use) in the table and store the metadata of Polygon or any shape as XML/JSON.
Here's link a https://developers.google.com/maps/documentation/javascript/geocoding#GeocodingResults
I´m working with Leaflet.js and I have a lot of markers but I want to get a polygon drawn automatically containing a specific group of markers.
There´s an image:
Every marker has a specific radio, so if a use it, would be like this:
but I don't want that, I want an area that contains markers, I don't know how can I do that.
You might want to create a convex hull.
https://gis.stackexchange.com/questions/215137/how-to-create-a-convex-hull-with-leaflet-points:
"The easiest way to do this with javascript is to use Turf.js's convex functionality."
A working sample - http://bl.ocks.org/ebrelsford/c31f61d39d2cd559e18a
i have my current lat,lon
and i want to make Bounding Box Search in GAE data store to get every nearest location to my current point .
i want the bounding box to be 1 km around my point
how can i do this ??
Check this example: http://code.google.com/appengine/articles/geosearch.html
It is in Python, but the discussion of the associated problems and ways to implement precomputed boxes could be helpful to you.
I'm using GeoDjango with PostGIS and trying to use a polygon to get records from a database which fall inside it.
If I define a polygon which is bigger than half the area of the earth it assumes the 'inside' of my polygon is the smaller area which I intended as the 'outside' and returns only results which are outside it.
I can just use this smaller, wrong area to exclude results. Polygon.area seems to know what I intend so I can use this to determine when to make my search inclusive or exclusive. I feel like this problem is probably common, is there a better way to solve it?
Update: If 180 degrees longitude is inside my polygon this doesn't work at all. It seems GEOS is to blame this time. This image shows what I believe is the reason. Green is the polygon I define, Red is how it seems to be interpreting it. Again this seems like a problem which would crop up often and one that libraries like GEOS are made to deal with. Is there a way?
Alright, no answers. Here's what I've done.
Because GEOS doesn't like things crossing the 180th meridian:
First check if the polygon crosses the 180th meridian - If so, break it into 2 polygons along that line.
Because PostGIS assumes a polygon is as small as possible you can't make one cover more than half the world, so:
Check if the polygon or each of the split polygons covers half the world or more - If so, break them in half.
Construct a MultiPolygon from the results.