Mysql Database design - Storing single and multi lat longs

Question

I have a mysql database table that will store locations for buildings and events and a few other things. All locations are stored in one table, and linked to buildings, events etc through their own many to many table. That way I can just display dots on a map, and also allow filtering etc.

However the problem comes with some things having a single location so 1 lat,long but some like a track has a number of lat long positions, and something like a large stadium might have a polygon over it. These are also stored as a list of lat,longs with the first and last being the same.

Im wondering how I should store this in the mysql db though. Originally I just had a column for lat, long and id for the lookup table. Should I have ANOTHER lookup table for the co-ordinates or serialise the data before putting it into the DB in some way or should I just store the whole string in one field lat1,long1 lat1,long1;lat2,long2;lat1,long1

Any suggestions?

Answer 1

Since you're not doing any lookups on the locations, and you're using (I'm assuming) Google Maps API, the simplest solution would probably be to encode a list of lat/lon as JSON and store in a varchar column.

You can just output the JSON straight from the database for your Google Maps API code to use. I would suggest you to use some simple JSON structure like so: ["point",1.23456,2.34567] or ["line",1.23456,2.34567,3.45678,4.56789] and so on.

Answer 2

I wouldn't de-normalize the data from the start, by pushing a whole "serialized" polygon into a single field.

Rather, I'd have a Polygons table (with polygon ID and possibly auxiliary per-polygon info, such as whether it's an actual closed polygon or just a polyline -- though that might alternatively be represented in the following table by having the last point equal to the first one for a certain polygon), and a PointsInPolygon table (with coordinates of the point, polygon ID foreign key, vertex number within polygon -- the latter two jointly being unique).

Normalization will make (as usual) your life much simpler for ad-hoc queries (including in this case "polygons near X", point in polygon, etc). Again as usual, you can later add redundant denormalized values if and when you determine that some specific query really needs to get optimized (at some cost to table updates, integrity checks, etc). Geodata are not all that different from other kinds in this regard.