Please start any new threads on our new site at We've got lots of great SQL Server experts to answer whatever question you can come up with.

Our new SQL Server Forums are live! Come on over! We've restricted the ability to create new threads on these forums.

SQL Server Forums
Profile | Active Topics | Members | Search | Forum FAQ
Save Password
Forgot your Password?

 All Forums
 SQL Server 2008 Forums
 Transact-SQL (2008)
 bulk loading large amount of spatial data
 Reply to Topic
 Printer Friendly
Author Previous Topic Topic Next Topic  

Flowing Fount of Yak Knowledge

2886 Posts

Posted - 03/17/2013 :  00:31:02  Show Profile  Visit jezemine's Homepage  Reply with Quote
hi folks! been a while since I asked or answered a question! glad to be back! :)

I need advice on loading a largish amount of spatial data in to SQL 2008 R2.

I have 13605 individual tab-delimited text files with data like this:

43.00000	-115.00000	1082
43.00000	-114.99917	1062
43.00000	-114.99833	1054
43.00000	-114.99750	1065
43.00000	-114.99667	1083
43.00000	-114.99584	1092
43.00000	-114.99500	1090
43.00000	-114.99417	1089
43.00000	-114.99334	1085
43.00000	-114.99251	1081
43.00000	-114.99167	1067
43.00000	-114.99084	1067
43.00000	-114.99001	1073
43.00000	-114.98918	1077
43.00000	-114.98834	1077
43.00000	-114.98751	1056

each file has 1442401 rows in it. the columns are: Latitude, Longitude, ElevationMeters. Basically this is elevation data for the whole planet, at about 90m resolution in x-y.

So the total number of rows is 19.6 billion. btw if you want this data it's freely available from USGS. It came from a satellite radar survey called SRTM.

I want to load this all into a table using a geography column so I can index it and do spatial queries against it.

My question is about how to load this data most efficiently. My plan was to do this:

1. create two tables:

-- for importing the text files
create table Elevation_stage(Latitude float not null, Longitude float not null, ElevationMeters smallint not null)

-- for storing the final result
create table Elevation(Point geography not null)

2. using a batch script, import files one at a time using bulk insert, then import from stage to the "real" table using insert/select. the body of the loop over files would be something like this:

truncate table Elevation_stage

bulk insert Elevation_stage from '%file%' with (BATCHSIZE=100000,TABLOCK)

insert Elevation
select geography::STPointFromText('POINT('+convert(varchar,Longitude)+' '+convert(varchar,Latitude)+' '+convert(varchar,ElevationMeters)+')', 4326)
from Elevation_stage

The problem is the insert/select takes a relatively long time, about 50 sec per file. It's 2x faster if I use geography::Point() instead of geography::STPointFromText(), but then I can't bake in the elevation value into the point because the Point() constructor does not take Z as a param. It only takes X,Y.

It's extremely stupid that Point ctor doesn't take Z as an arg but that's the way it is. STPointFromText() takes it, Point() does not. Lame.

here's Point, only takes lat/lon: (side note: extra lame also that Point takes args in lat,lon order, which is opposite the order STPointFromText wants...)

So if I go the Point() route, I'd have to add an ElevationMeters column to my Elevation table, like this:

create table Elevation(Point geography not null, ElevationMeters smallint not null)

then I could do the insert/select like this which is 2x faster.

insert Elevation
select geography::Point(Latitude, Longitude, 4326), ElevationMeters
from Elevation_stage

If you are loading 10^10 rows, factors of 2 matter. :)

Right now I am leaning towards the Point() route. The only real downside is the table will be about 20% bigger on disk when it's fully loaded, due to having the extra ElevationMeters column.

Any advice much appreciated! Is there a better way to load this data?


Flowing Fount of Yak Knowledge

2886 Posts

Posted - 03/17/2013 :  01:54:18  Show Profile  Visit jezemine's Homepage  Reply with Quote
I created a bug on connect for the deficiency of the Point() ctor. vote for it if you care :)
Go to Top of Page
  Previous Topic Topic Next Topic  
 Reply to Topic
 Printer Friendly
Jump To:
SQL Server Forums © 2000-2009 SQLTeam Publishing, LLC Go To Top Of Page
This page was generated in 0.02 seconds. Powered By: Snitz Forums 2000