Return Code Problems

Return code Problems caused by lack of proper Return code support in internal functions

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The intention is for a zoom base applications to retrieve information about usable zoom_levels

RasterLite2 is indended to be a Wms-based System

• where the use of Scales and Resolutions are used to maneuver around the supported area

Often such Resolutions are based on the Coordinate System being used

• as such, a common comparison is often not possible

Here Scales are more useful

• and that is what most Wms-clients use

Zoom-Levels also use Scales a base for determining the Zoom-Levels

• often, but not always, 1:4000 being set as Zoom 17

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Taking into consideration

• that there are many Zoom-Levels Applications exist and
• that many people essentially know what Zoom 17 implies

The major goal was to offer

• both Wms and Zoom-Level Applications
  • a range of Resolutions/Scale/Zooms-Levels
    • showing usable results

For Wms-Clients

• Wms 1.1.1 : ScaleHint
• Wms 1.3.0 : Min/Max-ScaleDenominator

For Zoom-Level-clients

• zoom_min
• zoom_max

Many User-Friendly Applications also offer a default

• (Center) Position
• zoom_default

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With this in mind, each raster_coverage, using RasterDefaults will store a

• default Center-Position
• and estimated min/default/max Zoom-Level

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For this an Sql-command has been developed to retrieve this information

• ['RL2_GetRasterCoverageDefaults(coverage_name)'] (RL2_GetRasterCoverageDefaults)
  • which will return 2 csv fields [separated with a ;]
    • center_x,center_y,center_srid [separated with a ,]
    • zoom_min,zoom_default,zoom_max [separated with a ,]

SELECT 
 coverage_name,
 RL2_GetRasterCoverageDefaults(coverage_name) 
FROM raster_coverages;

1861.world_mercators	           -1982.3723119,-1224.5405843,3395;3,5,7
1868.rote_rathausturm_panorama	   4987.5000000,502.0000000,-1;15,17,19
1927.436b_43668	                   6400.0000000,28000.0000000,3068;16,18,20
dritte_landesaufnahme_toscana	   28.5000000,43.0000000,4805;10,13,16
dritte_landesaufnahme_toscana_dir  28.5000000,43.0000000,4805;6,13,20

The original values are first calculated during

• 'RL2_LoadRaster'
  • Center-Point being the Center of the raster_coverage
  • zoom_default being based on the original raster resolution set in:
    • x_resolution_1_1
      • should result in original resolution of the image (100%)
  • zoom_min being based on the original raster resolution set in:
    • x_resolution_1_8 + 2 zoom_levels
      • should result in a usable overview of the whole raster coverage
  • zoom_max being based on the difference of zoom_default and zoom_min
    • zoom_max=zoom_default+(zoom_default-zoom_min)
      • an enlargement original resolution of the image (ca. 400%)

and updated during any following

• 'RL2_Pyramidize' or 'RL2_PyramidizeMonolithic'
  • zoom_min being based on the original raster resolution set in:
    • x_resolution_1_1 of the last pyramid

Afterwhich, a Database Designer, can adapt the values as needed with

• 'RL2_SetRasterCoverageDefaults'
  • either with both Center-Point and Zoom-Levels parameters
  • or Center-Point parameter only
  • or Zoom-Levels parameters only

SELECT RL2_SetRasterCoverageDefaults
(
 'dritte_landesaufnahme_toscana', -- raster_coverage name
 MakePoint(681582.6377649425,4849582.896019161,23032), -- center_point
 10, -- zoom_min
 14, -- zoom_default
 18  -- zoom_max
);

Validity rules:

• Center-Point
  • will be transformed to the srid of the raster_coverage when needed
  • must be inside the raster_coverage (after possible transformation)
    • if not the function will fail
• Zoom-Levels
  • must be between 0 and 30
    • values outside this range will be ignored
      • when you only want to set the zoom_default to 18
        • SELECT RL2_SetRasterCoverageDefaults('coverage_name',-1,18,-1)
  • zoom_min < zoom_default < zoom_max * if not the function will fail

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Resetting back to default values

• possible values of 2nd parameter
  • 0 = all values (Center-Point and Zoom-Levels)
  • 1 = Center-Point only
  • 2 = Zoom-Levels only

SELECT RL2_SetRasterCoverageDefaults
(
 'dritte_landesaufnahme_toscana', -- raster_coverage name
 0 -- 0,1 or 2
);

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2015-11-10: Mark Johnson, Berlin Germany

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