Creating Rasters from Scratch in PostGIS, Part 2

2017-03-24
#postgis #sql #raster #intro to postgis
database

Goal

In this post, we’ll learn how to create a multi-band raster from scratch using PostGIS. This ability will be particularly useful as we begin exploring the relatively uncharted waters of the PostGIS Raster Module.

Purpose:

This is a companion article for Creating Rasters from Scratch in PostGIS. I recommend reading it if you haven’t already to learn why you might want to do this as well as for a more detailed explanation of the parameters.

Getting Started

Let’s look at the code from our last post:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
-- Insert into our newly created table
-- Insert into that table
INSERT INTO public.test_250(rast)
SELECT ST_AddBand(
  -- Make empty raster
  ST_MakeEmptyRaster(
      1500, -- Raster width x (in pixels)
      1500, -- Raster width y (in pixels)
      -105.4330444336, -- Upper left X coordinate
      40.7170785158, -- Upper left Y coordinate
      0.00208333, -- X Cell Resolution (in degrees) (~250m)
      0.00208333, -- Y Cell Resolution (in degrees) (~250m)
      0, -- X skew
      0, -- Y skew
      4326 -- SRID (WGS 84)
    ),
    -- We're making a single band raster, but you can add
    -- as many bands as you like by adding additional rows
    -- to the array.
    ARRAY [
      ROW(
        1,  -- Band index: sets this as the first band
        '8BUI'::text,  -- Pixel Type (string rep of ST_BandPixelType types)
        5,  -- Initialized pixel value
        255  -- Nodata Value
      )
    ]::addbandarg[]
);

In order to add additional bands, all we have to do is add another row to our rasterbandarg[]:

1
2
3
4
5
6
7
INSERT INTO public.test_250(rast)
SELECT ST_AddBand( ST_MakeEmptyRaster(1500, 1500, -105.4330444336, 40.7170785158, 0.00208333, 0.00208333, 0, 0, 4326 ),
    ARRAY [
      ROW(1, '8BUI'::text, 5, 255),
      ROW(1, '8BUI'::text, 10, 255)
    ]::addbandarg[]
);

Yep. It’s really that easy!