polygon

问题 I have imported a world map dataset from www.GADM.org using the R package raster. I would like to clip it to a polygon I create to reduce the size of the map. I can retrieve the data and I can create the polygon no problem, but when I use the 'gIntersection' command I get an obscure error message. Any suggestions on how to clip my World Map dataset? library(raster) library(rgeos) ## Download Map of the World ## WorldMap <- getData('countries') ## Create the clipping polygon clip.extent <- as

问题 The program I am writing draws multiple stars on the screen and gives them random directions and speeds. The stars will bounce off the edges of the panel and stay inside. I need to have the stars rotating as they are moving. I have tried so many things and I cannot figure it out. Below is the code I use to draw the stars and move them. Additional Information: -the stars are in a collection called "stars" -there are two classes that I wrote, "Star" and "MyJPanel" Set the points: (in Star class

问题 The program I am writing draws multiple stars on the screen and gives them random directions and speeds. The stars will bounce off the edges of the panel and stay inside. I need to have the stars rotating as they are moving. I have tried so many things and I cannot figure it out. Below is the code I use to draw the stars and move them. Additional Information: -the stars are in a collection called "stars" -there are two classes that I wrote, "Star" and "MyJPanel" Set the points: (in Star class

问题 I've been looking for a way to check if a point is part of a polygon; this polygon is loaded from a file. All the answers related to this question are solved with javascript, but I require to do this on server-side; this because the result does not need to be shown to the user as a webclient, it needs to be stored and later be used as a parameter to select a group of users (that use the system) inside that area (polygon). I looked for a Google Maps API for PHP but it looks like it does not

问题 In the Displaying Overlays on a Map section of the iOS Developer Library Location Awareness Programming Guide, there is an example that "shows a filled and stroked overlay covering the state of Colorado." // Define an overlay that covers Colorado. CLLocationCoordinate2D points[4]; points[0] = CLLocationCoordinate2DMake(41.000512, -109.050116); points[1] = CLLocationCoordinate2DMake(41.002371, -102.052066); points[2] = CLLocationCoordinate2DMake(36.993076, -102.041981); points[3] =

问题 In the Displaying Overlays on a Map section of the iOS Developer Library Location Awareness Programming Guide, there is an example that "shows a filled and stroked overlay covering the state of Colorado." // Define an overlay that covers Colorado. CLLocationCoordinate2D points[4]; points[0] = CLLocationCoordinate2DMake(41.000512, -109.050116); points[1] = CLLocationCoordinate2DMake(41.002371, -102.052066); points[2] = CLLocationCoordinate2DMake(36.993076, -102.041981); points[3] =

问题 The Google Maps API for a Polygon does not offer a drag method. What would be an efficient way of implementing such a feature (i.e., sufficiently optimised so that it would not kill a four year old laptop)? Thank you! 回答1: I found the Google Maps V2 Polygon Implementation to be very limiting for the needs I have had and solved it by creating a custom overlay. My group is currently stuck on IE6 so I have yet to migrate over to Google Maps V3 - but taking a quick look at the API shows that you

问题 As far as I know, there is currently no way to display SVG polygons in the Raphael Javascript library. I'm building an application that needs to read in SVGs and them display them in Raphael, however, many of these SVGs use polygons. For example, I'm reading in an SVG with a polygon in this format: <polygon points="260.5,627.75 259.563,628.313 258.625,628.563 258.25... So, I'm wondering...is there a way to convert the polygon points into a path which I could draw in Raphael? I've seen a few

问题 I'm looking for advice on the best way to proceed. I'm trying to find whether a given point A:(a, b) is inside a regular hexagon, defined with center O:(x, y) and diameter of circumscribing circle. It seems like overkill to use Ray-casting, or Winding-number to determine this, for such a simple case, and I'm currently looking at the option of finding the angle (from horizontal) of the line OA, and "normalising" (probably not the right word) it into one of the 6 equilateral triangles and

问题 I have an app that find the shortest distance between my user to a polygon. I want to convert the polygon to Geofence to check the distance between the user to the area to give mor accurate information to the user. how can I do that? this is the MapsActivity public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, LocationListener, MinimumDistanceTask.GetMinimumDistanceListener { private GoogleMap mMap; private LocationManager manager; private double lat, lng; private