How to find accurate latitudes and longitudes data for cities?

Question

I want to put the coordinates of cities in a spatial db and then find cities from a given city at some given distance. I am hoping these functions would be readily available in a spatial db like PostGis. First, am I right in assuming this?

The problem I am facing though is this - I do not know where to store these coordinates from. I have this with me - http://download.geonames.org/export/dump/ and it has a 290 mb file (allcountries.zip) with coordinates of all cities but I am not sure how accurate it is. I am going to use this data to build something important so I want to know if someone here uses something more accurate or concise.

If the cities are much farther apart, just the latitudes and longtitudes won't do right? Will need something like spatial ref Ids also? Please suggest the right approach.

Also, given so much info, how does one proceed to find cities from a given city and given distance?

Answer 1

I am hoping these functions would be readily available in a spatial db like PostGis. First, am I right in assuming this?

You're asking if PostGIS can find points within a certain distance of a given point? Yes, it can.

I am going to use this data to build something important so I want to know if someone here uses something more accurate or concise.

What do you think is wrong with the dataset you have? Why not try it and see? Are you concerned there are too many small places in it?

If the cities are much farther apart, just the latitudes and longtitudes won't do right? Will need something like spatial ref Ids also?

If you're asking, does the data have to be in a projected format (with a given SRS identifier) in order to do what you want, then no - there's no problem either using the data in its current unprojected form (EPSG:4326) or projecting it to another system if needed.

How does one proceed to find cities from a given city and given distance?

See Return all results within a 30km radius of a specific lat/long point?

Answer 2

Depending on what you like I think you have a few options available. You will need two components

1. The Location of the cities X,Y
2. An Origin Destination Matrix (this requires a Network in order to function)

OpenSource: Section 1(the location of the cities)

• You could take a look at the Cultural Vectors from Natural Earth; OR
• You could look into using Overpass Turbo which will pull in OpenStreetMap Data using a snippet of code below

node [place=city]({{bbox}}); out; the Overpass API Language can consume the Place Tags from the OpenStreetMap Tags

Section 2(an origin destination matrix)

• Take a look at Turf JS Distance Module (This will be hard coded and very miserable to do); OR
• take a look at PGRouting to create a network of roads using Natural Earth Roads

Google:

Section 1(the location of the cities)

• using natural earth data above, gather the Lat/Long of each city

Section 2(an origin destination matrix)

• Use the Distance Matrix Service; OR
• Use the Google Distance Matrix API

ArcGIS Online

You can use the Connect Origins to Destinations function on ArcGIS Online

Answer 3

There is no absolute accuracy in city coordinates.

For example, New York City is 1214 km² large, and there is no definition which point is New York City. You can take the centroid of the border, or the Town Hall, or any point within the border you might prefer.