I have 20 000 polygons in a dataset. I need to have the Euclidean Distance between all polygons, so a 20 000 x 20 000 distance matrix where for each of the polygons, the distance to all other polygons is stored.
I have read in some other threads the recommendation to use the "Near" tool in Arcmap. However, this tool only calculates the distance to the NEAREST polygon, while I need the distance from ALL polygons to ALL polygons.
Is there any solution for this?
Near tool: Calculates distance and additional proximity information between the
input features and the closest feature in another layer or feature
class.
In order to calculate the distance between the centroids of each of your polygons make sure your map is in a projected coordinate system.
Then, make sure the centroid points are calculated (detailed step-by-step here: https://support.esri.com/en/technical-article/000009381 )
Export your centroid point attribute table as a DBF (Click on Options > Export.)
Add the table to your map. Right click on the new table, Display XY Data, select Longitude for the X and Latitude for Y, and select the map's coordinate system to create an events layer.
Then, use the Point Distance tool (Details here: https://desktop.arcgis.com/en/arcmap/10.3/tools/analysis-toolbox/point-distance.htm ). The event points are both the input and near features. The output will be a table displaying distance between all polygon centroids on the map.
Related
Basically what I'm looking for is an algorithm or an extension similar to least cost analysis, but instead of using points on top of a DEM to create a path (line vector) between the points, I whish to create a Thiessen (Voronoi) polygons (centered on points), whose spatial limits would be defined by the DEM.
So for example, a border between 2 polygons would be determined by the least cost analysis between the center points of the 2 polygons. The aim would then be, instead of getting a set of Thiessen polygons with arrow-straight borders (like in the pic), to create a set of polygons whose limits would be determined by the DEM (relief). Sort of like a watershed centered on a single point.
Btw, it would be great if there was a solution applicable in QGIS.
Thanks!
If I have a list of points in 3D space that are only roughly located on a surface, this surface can be visualized with ListSurfacePlot3D in Mathematica. How can I find the intersection of this approximate surface with a plane, that spans between two vectors u and v? And to continue this, how would I find the intersection of the resulting line with another plane that spans between two vectors m and n?
The dataset of points is available here: https://www.dropbox.com/s/rlj91jrh1bp4g2c/data.txt?dl=0
I need to get relative lateral coordinates (distance to the vehicle from one side of the lane i.e Px) of vehicles.
I know that SUMO provides absolute x,y coordinates and distance traveled (Py).
Is there a way to get Px information at each timestep directly like Py?
This information is part of the raw dump (or netstate dump, see https://sumo.dlr.de/wiki/Simulation/Output/RawDump) but only if the sublane model is active. It is given as an absolute deviation from the center line of the line (which is always 0 if the sublane model is not active).
I have a number of 2D (possibly intersecting) polygons which I rendered using OpenGL ES on the screen. All the polygons are completely contained within the screen. What is the most timely way to find the percentage area of the union of these polygons to the total screen area? Timeliness is required as I have a requirement for the coverage area to be immediately updated whenever a polygon is shifted.
Currently, I am representing each polygon as a 2D array of booleans. Using a point-in-polygon function (from a geometry package), I sample each point (x,y) on the screen to check if it belongs to the polygon, and set polygon[x][y] = true if so, false otherwise.
After doing that to all the polygons in the screen, I loop through all the screen pixels again, and check through each polygon array, counting that pixel as "covered" if any polygon has its polygon[x][y] value set to true.
This works, but the performance is not ideal as the number of polygons increases. Are there any better ways to do this, using open-source libraries if possible? I thought of:
(1) Unioning the polygons to get one or more non-overlapping polygons. Then compute the area of each polygon using the standard area-of-polygon formula. Then sum them up. Not sure how to get this to work?
(2) Using OpenGL somehow. Imagine that I am rendering all these polygons with a single color. Is it possible to count the number of pixels on the screen buffer with that certain color? This would really sound like a nice solution.
Any efficient means for doing this?
If you know background color and all polygons have other colors, you can read all pixels from framebuffer glReadPixels() and simply count all pixels that have color different than background.
If first condition is not met you may consider creating custom framebuffer and render all polygons with the same color (For example (0.0, 0.0, 0.0) for backgruond and (1.0, 0.0, 0.0) for polygons). Next, read resulting framebuffer and calculate mean of red color across the whole screen.
If you want to get non-overlapping polygons, you can run a line intersection algorithm. A simple variant is the Bentley–Ottmann algorithm, but even faster algorithms of O(n log n + k) (with n vertices and k crossings) are possible.
Given a line intersection, you can unify two polygons by constructing a vertex connecting both polygons on the intersection point. Then you follow the vertices of one of the polygons inside of the other polygon (you can determine the direction you have to go in using your point-in-polygon function), and remove all vertices and edges until you reach the outside of the polygon. There you repair the polygon by creating a new vertex on the second intersection of the two polygons.
Unless I'm mistaken, this can run in O(n log n + k * p) time where p is the maximum overlap of the polygons.
After unification of the polygons you can use an ordinary area function to calculate the exact area of the polygons.
I think that attempt to calculate area of polygons with number of pixels is too complicated and sometimes inaccurate. You can see something similar in stackoverflow answer about calculation the area covered by a polygon and if you construct regular polygons see area of a regular polygon ,
as topic, the Coordinates value (Latitude and Longitude) is known , these Coordinates will compose as polygonal area , my question is how to calculate the area of the polygonal that is base the geography ?
thanks for your help .
First you would need to know whether the curvature of the surface would be significant. If it is a relatively small then you can get a good approximation by projecting the coordinates onto a plane.
Determine units of measure per degree of latitude (eg. meters per degree)
Determine units of meature per degree of longitude at a given latitude (the conversion factor varies as you go North or South)
Convert latitude and longitude pairs to (x,y) pairs in the plane
Use an algorithm to compute area of a polygon. See StackOverflow 451425 or Paul Bourke
If you are calculating a large area then spherical techniques must be used.
If I understand your question correctly - triangulation should help you. Basically you break the polygonal to triangles in such a way that they don't overlap and sum their areas.