[mapserver-users] Plotting points as a line from sqlite database

[Stephen Woodbridge]

On 6/29/2011 10:13 PM, Ian Walberg wrote:
> I hope this isn't too stupid a question.
>
> Would like to display a list of positions in an sqlite database as a
> line, to show the flight path of an aircraft. The data is in the db as
> Lat, Long and point (lat, long)
>
> We can display the positions as individual dots but not as a line, I
> fear the problem is that the data is a point.
>
> As the data is being accumulated we would prefer not to create a new
> line in the database each time if possible.
>
> Any suggestions to what options we have would be appreciated.

Hi Ian,

In postgis there is an aggregrate function makeline() that you can feed 
points to. I think there may be an equivalent function in SpatiaLite.

In sqlite, you might be able to use a group_concat() something like:

select 'LINESTRING('|| group_concat(lat||' '||long, ',') ||')'
   from points;

But I think the issue will be that this is not a format that mapserver 
understands. You might be able to access this via GDAL/OGR but I'm not 
sure on that.

-Steve W