Voronoi diagrams - an interesting thing, only a very tricky food warmers buffet area there will be

* Is there a good plugin heatmap to immediately scale could ask, and do not bother with setting a blur and so on? * What's the easiest way to make, say, a tile layer with that? * If anyone wants to own the world, sql query is written, you can layer for the whole world to start.
# 4 04/03/2014 12:53:58
And what else? The density of the road network can count only on a particular polygon, say the square of 1 km by 1 km. One can not tell what is the density of the road network in the given point, only for landfill, in which it is situated.
# 7 03/05/2014 11:10:54
siberiano, you can collect all lines of roads, break them up points at regular intervals, to construct the Voronoi polygons to points, calculate the area of polygons, or rather the landfill area fraction to the entire area of the region of interest. As I understand it is not quite density food warmers buffet map - but something close. This can be done in the vector. Voronoi polygons can build yourself, you can use JTS, it is possible to cut the line and / simplified.
siberiano, you can collect all lines of roads, break them up points at regular intervals, to construct the Voronoi polygons to points, calculate the area of polygons, or rather the landfill area fraction to the entire area of the region of interest.
We do not face the task "to get a card with the distribution just something", and more particularly worth - "get a map of the distribution of something that has meaning." So, map the distribution proschadey such polygons (or arbitrary functions of one variable from them) to the road network does not make sense.
Map densities food warmers buffet answers the question how many dots per square kilometer. km. through gaps in this area. Polygon area Voronoi diagram answers the question of how many square meters. km per 1 dot (in the sense that the distance from any point within the Voronoi polygon before the points for which it is built smaller than to any other point in the construction uchvstvovavshey).
# 11 2014-03-05 16:31:53
I would also add, siberiano not say how he is going to use if you need just a picture food warmers buffet - then the vector to fool makes no sense. The described method allows food warmers buffet the same for every point of the road to estimate what the area around the point of the space within which the point under consideration is short. Summing weight food warmers buffet points form a line, it is possible to obtain an estimate for the line, as far as large a territory for which this line is the nearest (not an exact value but a good approximation);
Re: On what can make a map of density?
100 pixels for Moscow - is if you count the squares to 1 * 1 km. But from every point in space can be measured square or circle an area of 1 square kilometers and calculate for him. Can other areas, food warmers buffet and counted on the square. km. So there is a lot of interpretations.
Voronoi diagrams - an interesting thing, only a very tricky food warmers buffet area there will be divided, and the map will look chopped, with unnatural boundaries (for example, if the road is sticking out of the corner of the city in a dense field, the angular point of capturing many areas, and the map will be a wedge of low density ). Maybe not, but I think that generate these charts - far too much work
You just need to decide to what detail you need this card (which should follow directly from the final problem you want to solve the construction of the map). Indeed, it is theoretically possible to construct a pseudo-continuous (as opposed to discrete) distribution diagram of the density, for example, with a resolution of 1 meter / pixel, beating the entire area with a step equal to the resolution, and for each point considering the length of roads in the vicinity food warmers buffet of any type (like - square, want - round) of any size, for example - an area of 1 sq km. This naturally requires cost nefigovyh computing power. But the question is, what for such detail is needed. I can not imagine what practical benefit topikstarter going to learn from this metric, but for some illustrative purposes should food warmers buffet be enough far more discreteness. And beauty can this value to smooth interpolation.
And so these scripts, which it is generated. If you bring a little bit, and you can generate tiles. food warmers buffet https://bitbucket.org/siberiano/postgis-raster-heatmap
Layer of the source data (points with weights) are stored in the table. For convenience, in QGIS filing a column in geometry_columns (http://postgis.net/docs/AddGeometryColumn.html) - then the program will not scan all the data from the table.
Spots appear in the bed. Check to see whether the desired projection. If not - you have to re-create the project and the layer, otherwise I could not get the correct food warmers buffet Heat map (it would be disproportionate, and all circles become ellipses).
Now add a layer heatmap, it selects the appropriate settings (which is the field of weighing, blur radius and the size of the points). If the size is meaningless points (ie in my obviously too much latitude columns), re-create food warmers buffet the project (other projection was chosen, food warmers buffet and why change something on the go is impossible to make a normal dimension Heat map).
To learn receptacle