geospatial

问题 Currently I have a few tables with 100k+ rows. I am trying to lookup the data like follows. SELECT *, SQRT(POW(69.1 * (latitude - '49.1044302'), 2) + POW(69.1 * ('-122.801094' - longitude) * COS(latitude / 57.3), 2)) AS distance FROM stops HAVING distance < 5 ORDER BY distance limit 100 But currently this method slows with high load. Some queries are taking 20+ seconds to complete. If anyone knows any better ways to optimize this would be great. 回答1: Well first of all if you have a lot of

问题 I need to implement a Geo proximity search in my application but I'm very confused regarding the correct formula to use. After some searches in the Web and in StackOverflow I found that the solutions are: Use the Haversine Formula Use the Great-Circle Distance Formula Use a Spatial Search Engine in the Database Option #3 is really not an option for me ATM. Now I'm a little confused since I always though that the Great-Circle Distance Formula and Haversine Formula were synonymous but

问题 I'm evaluating Magento for a travel company who will need to do product searches and recommendations based on geographical distance. The company is creating custom holiday packages based on various components (eg: accommodation, tours, restaurant vouchers, etc). These components potentially have overlapping locations (ie: a particular tour might be close enough to several hotels to be considered related to each of them). As a user builds up their custom package by adding stays at various

问题 I have this gridded data that I want to plot on a US map: https://www.dropbox.com/s/9khcjgtv8ipo2u5/windspeed.txt?dl=0 library(ggplot2) library(RColorBrewer) library(rgdal) library(sp) library(maps) options(max.print=5.5E5) all_data = read.table("windspeed.txt",header = TRUE) res=0.01 #spacing of row and col coords pre-specified origin_lat_lon=c(24.55, -130) all_data$row=(all_data$row)*res+origin_lat_lon[1] all_data$col=(all_data$col)*res+origin_lat_lon[2] coords = cbind(all_data$col, all

问题 I have an issue when I try to aggregate results with a geospatial condition : db.users.group({ reduce: function(obj, prev) { prev.sums = { y_levels: prev.sums.y_levels + obj.current_y_level, x_levels: prev.sums.x_levels + obj.current_x_level, count: prev.sums.count + 1 } }, cond: {current_position: { $near: [56.553823, 8.565619, 10]}}, initial: { sums: { y_levels: 0, x_levels: 0, count: 0 } } }); produces : uncaught exception: group command failed: { "errmsg" : "exception: manual matcher

问题 I have a shape file, uploaded at the following path: https://drive.google.com/open?id=0B1ITb_7lHh1EUFVfVWc4ekRfSnc I imported the data using the "read.shapefiles" function in "shapefiles" package: landuse<- read.shapefile("landuse") I now need to extract the lat/long centroids of all the shapes within the landuse object and add it to the landuse$dbf dataframe I tried two things: lu_df<-coordinates(landuse) lu_df<-SpatialPoints(landuse) Both gave me the following error: Error in coordinates(as

问题 I've created a database where one of the tables stores the geolocation of some points. I'm trying to fill that table, which a priori seems pretty easy with GeomFromText('POINT(39.48280 -0.34804)') , but it doesn't work. All the other columns, like id, name... do get their values, but the location column remains empty. So then I try to update the row I've just added with: UPDATE `pfc_db`.`poi` SET `location` = GeomFromText('POINT(39.48280 -0.34804)') WHERE id = 'poi00001'; And MySQLWorkbench

问题 I have some triples that represent the locations of several cities. I want to be able to fire off a Prolog query like (select (?x ?y ?dist) (q- ?x !exns:geolocation ?locx) (q- ?y !exns:geolocation ?locy) (geo-distance ?locx ?locy ?dist)) but I get this error: Server returned 400: attempt to call '#:geo-distance/3' which is an undefined function. I'd like to understand how to use the geospatial reasoning methods like geo-distance (I assumed it was built-in because they use it here. Is this not

问题 How do I convert SRID 3857 formatted geometery coordinates into to decimal degrees? My current stack is SQL Server 2014 and C#. 回答1: You cannot convert them directly in SQL Server. Quite simply it wasn't built to reinvent the Reprojection of spatial data in one datum to another. When using SqlGeography, you can of course swap between SRIDs when both sets of coordinates use the same coordinate-type (decimal-degrees or grid-based), however when using SqlGeometry, they are simply planar

问题 SQL Spatial Features: SQL geometry Point, Linestring working well but the Circular string is not working. When i try to save the CircularString type data to my geometry datatype its throws the following error: My statement: DECLARE @g1 geometry = 'CIRCULARSTRING EMPTY'; "A .NET Framework error occurred during execution of user-defined routine or aggregate "geometry": System.FormatException: 24114: The label CIRCULARSTRING EMPTY in the input well-known text (WKT) is not valid. Valid labels are