wiki:WKTRaster

Version 66 (modified by pracine, 10 years ago) (diff)

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PostGIS WKT Raster Home Page

Quick Links

What's new about WKT Raster?

December 4, 2009 - Jorge Arevalo full time on WKT Raster!
Jorge Arevalo who developped the first version of the GDAL WKT Raster driver during the summer of 2009 will be working for at least one year on WKT Raster. Jorge was recently hired by DEIMOS Space, a Spanish aerospace company and Jorge's superior, Miguel Lizondo, confirmed that Jorge would be devoting most of his time to WKT Raster in the coming year. This commitment should normally be extended for a second year afterward.

Jorge will follow the planned roadmap and will be the main developper for the coming year. Mateuzs Loskot will continue contribute his spare time to the project and Pierre Racine will help Jorge with the specifications and the general management of the project.

Welcome (back) Jorge!

October 16, 2009 - PostGIS WKT Raster at Geomatique 2009 in Montréal!
Pierre Racine will present WKT Raster at Geomatique 2009 in Montréal on October 20. We hope we can get more people interested by the project! See the presentation (PDF)!

June 04, 2009 - A prototype GDAL driver to WKT Raster implemented this summer!
Thanks to Mateusz Loskot, who proposed the Google Summer of Code project and Jorge Arevalo the student who was selected to implement it.

Welcome to the WKT Raster project home page!

PostGIS WKT Raster is an ongoing project aiming at developing raster support in PostGIS. It is a new project very different from the previous PGRaster project and also very different from Oracle Spatial GeoRaster.

The goal of WKT Raster is to implement the RASTER type as much as possible like the GEOMETRY type is implemented in PostGIS and to offer a single set of overlay SQL functions (like ST_Intersects) operating seamlessly on vector and raster coverages.

Development Info

  • Planning - Beta 0.1.6 PostGIS WKT Raster should happen by july 2010. Look at the planning page for a detailed schedule and to know how to contribute.
  • Source Code - PostGIS WKT Raster source code is available from the OSGeo Subversion repository
    svn checkout https://svn.osgeo.org/postgis/spike/wktraster wktraster
    
    API reference is available on WKT Raster Doxygen pages.
  • PowerPoints

    • Original Project Presentation - rationale, examples and preliminary specifications: PPT, PDF (v1.0)
    • Introduction to WKT Raster - Geomatique 2009, Montréal, october 2009. PDF

Overview of Planned PostGIS WKT Raster Functionalities

WKT Raster...

...is as simple as PostGIS...

  • one table = one raster coverage (like a vector coverage)
  • one row = one tile or one raster object (like a vector coverage where one row = one geometry)
  • only one new type: RASTER (like the PostGIS GEOMETRY type)
  • each raster tile has a pixel size, a width and a height, a variable number of band, a pixel type per band and a nodata value per band. Everything essential to do base raster GIS operations.

...is an extension of PostGIS to be installed separately

  • merge with PostGIS might occur in the future...

...has an import/export mechanism similar to shp2pgsql

  • raster2pgsql and pgsql2raster utilities allowing import/export of a single raster or a batch of raster into a tiled coverage.

...allows easy conversion from/to geometry/raster...

  • ST_AsPolygon(raster) -> geometry
  • ST_AsRaster(geometry, pixelsize) -> raster

...implements base GIS raster operations available in most GIS...

  • ST_Resample(raster, pixelsize, method) -> raster
  • ST_Clip(raster|geometry,geometry) -> same type as first argument
  • ST_Reclass(raster|geometry,string) -> same type as first argument
  • ST_MapAlgebra(raster|geometry, raster), mathematical expression, "raster"|"geometry") -> raster/geometry
  • etc...)

...introduces raster/geometry seamless geometry constructors...

  • so you don't have to bother whether the layers are in raster or vector form when using analysis functions.
  • ST_Intersection(raster|geometry, raster|geometry, "raster"|"geometry") -> raster/geometry
  • ST_Union(raster|geometry, raster|geometry, "raster"|"geometry") -> raster/geometry
  • ST_Accum(raster set|geometry set, "raster"|"geometry") -> raster/geometry
  • ST_Transform(raster|geometry, SRID) -> same type as input
  • etc...

...and seamless geometry operators...

  • ST_Intersects(raster|geometry, raster|geometry) -> boolean
  • ST_Contains(raster|geometry A, raster|geometry B) -> boolean
  • etc...

...allows raster storage INSIDE the database (as WKB)...

  • for efficient overlay analysis operations between vector and raster layers...

...or OUTSIDE the database (as JPEG or TIFF)...

  • so desktop and web applications can quickly access and load raster tiles and nevertheless benefits from the powerful PostGIS GiST spatial index. Every WKT Raster SQL functions working with in-db raster tiles work seamlessly with out-db raster tiles.

...introduces the concept of raster objects...

  • geographic features are stored as variable size raster tiles instead of polygons.
  • allows vector to raster conversion without lost of information.

...is much more simple than PGRaster and Oracle GeoRaster! WKT Raster supports...

  • only one type (instead of two in Oracle Spatial: SDO_GEORASTER & SDO_RASTER). In WKT Raster there are no differences between rasters and tiles: a tile is a raster and a raster is a tile. i.e. one row = one tile = one raster; one table = one raster coverage.
  • no metadata (like PostGIS)
  • no masks (you can create a mask as a band)
  • no multiple dimensions (only two: x, y). Not to be confused with bands; WKT Raster DO supports multiband raster...
  • no pyramids (reduced resolution coverages can be stored as a separate layer)

What do people think about WKT Raster?

Paul Ramsey:

This proposal is better than any I have seen, addresses solving problems that if solved will provide actual new functionality and benefit to users, and clearly you've thought this through over some time

Regina Obe:

The functions WKT Raster proposes look pretty cool actually and my vision of the benefits of storing raster in the database are covered in it

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