1,065 reputation
714
bio website emapsite.com
location Barcelona, Spain
age
visits member for 4 years, 2 months
seen 4 hours ago

I am a data architect (well I wrestle with large amounts of data and long running queries) specializing in GIS. I am also very interested in NoSQL and machine learning. Mountain biking, the taller the mountain the better, keeps me sane otherwise.


12h
comment Spatial search performance on a collection of Points in a PostGis database
Creating lots of buffers is a bad idea at query time. I'm still not entirely clear what you are trying to do: can't you just buffer a single search polygon and find all points inside it -- which will be efficient as it will use the index and only involve buffering one object?
12h
comment Spatial search performance on a collection of Points in a PostGis database
@Vince. Really. I have tables of 500 million geometries that return everything inside a search polygon in milliseconds, just using a Gist index.
16h
comment Spatial search performance on a collection of Points in a PostGis database
Sorry, I am half asleep, st_contains with a point against a point will not be efficient. Your search geometry should be a buffered point.
17h
comment Spatial search performance on a collection of Points in a PostGis database
This is what spatial indexes are designed to do, efficiently -- essentially build a sequence of successively smaller boxes to efficiently search in 2d. There is no substitute for testing, but 10 million is well within Postgres/Postgis's capabilities and if you start buffering things, you are adding complexity for no extra performance gain.
1d
comment What are good colour schemes for large density flow maps?
Cyan to chartreuse. Bring it on :D
1d
comment What are good colour schemes for large density flow maps?
What do you see in a shades of red color ramp as a matter of interest. I recently learnt just how many people are green/red colorblind. Guess traffic lights were invented before people knew this?
1d
comment How to store lat/long in PostGIS database?
Use ST_DistanceSphere if you want lat/lon and distance in meters. Where did you get the idea that ST_Intersect doesn't work in 4326?
1d
comment PostGIS 1.5 libstdc++ error
Have you tried sudo ldconfig? Also, what version did you upgrade from and to?
2d
answered How to update raster metadata in postgis
2d
comment Ideal file format for QGIS that allows mixed geometry types?
The Postgis geometry and geography types can both contain any mixture of points, lines, polygons and the multi versions thererof, so, yes, you could certainly use Postgis as a backend. If you import the WKT as a text field and then use ST_GeomFromText to update a geometry/geography field, then you will end up with all your geometries in one field with associated attributes -- that you can filter by.
2d
comment Still no fictional geographies in some GIS format?
Are you prepared to use Postgis? If so, postgis.net/docs/RT_ST_DumpAsPolygons.html, for your 2nd question.
2d
comment Add Google Maps Layer to OpenLayers Page
Which version of Ol are you using. I mean 2.x.x not 2 or 3. Sometimes the function defs change.
Oct
22
comment Add Google Maps Layer to OpenLayers Page
Looks like you are importing google maps api, which you don't need, and not open layers, which you do
Oct
22
comment openlayers display Control.MousePosition on div.olMap
That is the default behavior -- that it sits above and inside map div. Perhaps you could post a jsfiddle or similar.
Oct
22
comment openlayers display Control.MousePosition on div.olMap
Can you not just override the css from olControlMousePosition and the associated control?
Oct
21
comment Openlayers popup for markers issue
This is why it is usually a good idea to post a minimal working example :D
Oct
21
comment Most efficient way to intersect overlapping polylines
You can run ST_Union in Postgis on Lines too. I don't completely understand your problem description, but when I have insanely complex intersection problems (millions of polygons against millions of polygons), I usually break it down into smaller chunks -- divide and conquer style that you learn in algorithms classes -- and then merge the results afterwards. This involves writing plpgsql (my language of choice) functions, but you could do the same in shapely, I'm sure. I have got orders of magnitude performance boosts over a straight intersection/union with spatial join approach.
Oct
21
comment calling gdal_merge.py into another python script running GDAL processes
I think you can do all three in one line, but I have never tried. The order or operations presumably matters -- if you are clipping to input or reprojected srid. Think you'll have to test that.
Oct
21
revised Order of polygon vertices in general GIS: clockwise or counterclockwise
added 164 characters in body
Oct
21
comment Order of polygon vertices in general GIS: clockwise or counterclockwise
Also a nice answer. +1 for it's a wild world :-)