簡(jiǎn)介

柵格數(shù)據(jù)由按行和列（或格網(wǎng)）組織的像元（或像素）矩陣組成，其中的每個(gè)像元都包含一個(gè)信息值（例如溫度）。

柵格數(shù)據(jù)可以是數(shù)字航空像片、衛(wèi)星影像、數(shù)字圖片或掃描的地圖。

Ganos時(shí)空引擎通過在ADB PG中實(shí)現(xiàn)柵格數(shù)據(jù)模型，可以借助于數(shù)據(jù)庫(kù)的技術(shù)和方法高效地對(duì)柵格數(shù)據(jù)進(jìn)行存儲(chǔ)和分析操作。

快速入門

• 創(chuàng)建擴(kuò)展

  Create extension ganos_spatialref;
  Create extension ganos_geometry;
  Create Extension Ganos_Raster;

• 創(chuàng)建柵格表

  -- 指定raster 列作為表的 distributed column
  Create Table raster_table(id integer, raster_obj raster) 
  DISTRIBUTED BY (raster_obj);

• 從OSS中導(dǎo)入柵格數(shù)據(jù)

  Insert into raster_table 
  Values(1, ST_ImportFrom('chunk_table','OSS://<id>:<key>@oss-cn.aliyuncs.com/mybucket/data/my_image.tif')),
  (2, ST_CreateRast('OSS://<id>:<key>@oss-cn.aliyuncs.com/mybucket/data/my_image.tif'));

• 查詢柵格對(duì)象信息

  Select ST_Height(raster_obj),ST_Width(raster_obj) From raster_table Where id = 1;
   st_height 
  -----------
        1241
  (1 rows)

• 創(chuàng)建金字塔

  DO $$
  declare
      rast raster;
  begin
      select raster_obj into rast from raster_table where id = 1;
      rast = st_buildpyramid(rast);
      update raster_table set raster_obj = rast where id = 1;
  end;    
  $$ LANGUAGE 'plpgsql';
  
  DO $$
  declare
      rast raster;
  begin
      select raster_obj into rast from raster_table where id = 2;
      rast = st_buildpyramid(rast, -1, 'Near', 'chunk_table');
      update raster_table set raster_obj = rast where id = 2;
  end;    
  $$ LANGUAGE 'plpgsql';

• 根據(jù)視口的世界坐標(biāo)范圍，長(zhǎng)和寬來(lái)計(jì)算最佳的金字塔層級(jí)

  Select ST_BestPyramidLevel(rast, '((128.0, 30.0),(128.5, 30.5))', 800, 600) from raster_table where id = 1;
  
  ---------------------
  3

• 獲取柵格指定范圍像素矩陣

  DO $$
  declare
      rast raster;
  begin
      select raster_obj into rast from raster_table where id = 1;
      rast = st_buildpyramid(rast);
      Select ST_Clip(rast, 0, '((128.980,30.0),(129.0,30.2))', 'World');
  end;    
  $$ LANGUAGE 'plpgsql';

• 計(jì)算裁剪的像素坐標(biāo)范圍

  Select ST_ClipDimension(raster_obj, 2, '((128.0, 30.0),(128.5, 30.5))') 
  from raster_table where id = 1;
  
  ------------------------------------
  '((600, 720),(200, 300))'

• 刪除擴(kuò)展

  DROP Extension Ganos_Raster;
  DROP extension ganos_geometry;
  DROP extension ganos_spatialref;

SQL參考

詳細(xì)SQL參考請(qǐng)參見Raster SQL參考。