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Jan
30
comment Feature selection of one vector layer based on another vector layer: Any advice for using PostGIS or Python with PostGIS together?
For point 2 you can also use ST_ClosestPoint
Jan
30
comment Feature selection of one vector layer based on another vector layer: Any advice for using PostGIS or Python with PostGIS together?
Why not just use the closest road? That is what you want, isn't it?
Jan
29
comment Feature selection of one vector layer based on another vector layer: Any advice for using PostGIS or Python with PostGIS together?
In PostGIS you should think in terms of ST_DWithin (measuring distances) instead of intersecting buffers. And as said before. 50000 points is a small dataset. That is good news, isn't it :-)
Jan
29
comment Feature selection of one vector layer based on another vector layer: Any advice for using PostGIS or Python with PostGIS together?
I don't understand what you mean by "otherwise the system searches within 50 m buffer".
Oct
21
comment How do I find points that are NOT within a list of polygons using MS SQL?
Interesting. I haven't done any testing about performance in MS Sql. But some years ago I found the "not in" method slower in PostGIS. I might try it with the same data set in PostGIS and MS sql if I find time.
Oct
21
comment How do I find points that are NOT within a list of polygons using MS SQL?
@mapBaker, I have added an example in my answer
Oct
17
comment How do I find points that are NOT within a list of polygons using MS SQL?
@mapBaker, But in this case you will be joining on those actually intersecting, and then finding the ones that doesn't intersect any polygon at all because they don't get any polygon id in the join but instead just null. I will try it when I get to a SQL Server installation.
Oct
16
comment How do I find points that are NOT within a list of polygons using MS SQL?
@mapBaker Interesting. Is it only right join that has limitations like this in Sql Server? Or is it all outer joins? Do you have a link about it?
Oct
16
comment Identifying overlapping time intervals with two more criteria in R?
I am not sure I understand fully, but it seems like a task that is fairly straight forward in PostgreSQL. There is functions for time ranges. As I have understood it should be easy to share data between PostgreSQL and R.
Oct
11
comment Difference between Envelope and BoundingBox
at least in PostGIS there as a box3d ...
Sep
29
comment point returned from ST_LineLocatePoint returns false in ST_Contains
you are right that it is about rounding errors, but st_Closestpoint will not help. You get the same error problem. Actually there is many points along a line that cannot be described with a finite number of decimals. So use st_dwithin for exampke with a small tolerance instead of st_contains.
Sep
29
comment Efficiency in PostGIS: objects near point- ST_Intersects around buffer Vs ST_DWithin
I recommend taking a look in pgAdmin or psql or something else that can show what you have in the database. Create a column in your table where you put your transformed geometries. create a spatial index on that column. run analyze table_name to make planner collect some data about the table and index. put keyword explain in front of your query and look in the output for "index scan"
Sep
29
comment Efficiency in PostGIS: objects near point- ST_Intersects around buffer Vs ST_DWithin
:-) the standard rekomendation from PostGIS people is ST_DWithin. But I have seen cases where buffer/intersects is faster. Esri-people tend to recommend buffer/intersectm I think that is the Esri approach.
Jul
1
comment Mirrored shape in postgis
What do you mean by mirrored shapes? Why collections because of holes? A polygon can have holes. About eauality, why not use ST_Equals?
Jun
18
comment Creating quadtree index on latitude, longitude data in PostGIS
Why do you want that?
Apr
7
comment ST_MakePoint returns an error when using Python
Take a look at the log of the postgresql server. There you will see how the query is received from python to PostGIS.
Apr
2
comment st_length column in Postgres db and ArcGIS under WGS84
If it is PostGIS that populates that length column, the PostGIS doc is the place to look. Second sentance: postgis.net/docs/manual-2.1/ST_Length.html
Mar
23
comment Increase buffer until value is reached?
Well, 600 points to compare to 300k points is not that much. With a spatial index it is close to nothing :-). And if you combine sales points and dealers by some attribute instead of doing it spatial by distance it is even cheaper.
Mar
19
comment How to select distinct geometries and ids with PostGIS?
And if you want to be sure to get the first occurrence in the table, you have to sort on something giving the right order. I don't think that the row order is guaranteed.
Mar
19
comment How to select distinct geometries and ids with PostGIS?
A note: This will compare the bounding box, not the actual geometry. So, two geometries that share the exactly same bounding box will be regarded as the same, and only 1 of them will be returned. It is much safer (and faster) to use id if you have.