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<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">I have created a table loading via raster2psql:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">raster2pgsql -a -f Spatial_Grid -F -I -M -T ssa_data -X ssa_data *.tif ssa.TERRAIN_GRID<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">The tif data comes from
<a href="http://dwtkns.com/srtm/">http://dwtkns.com/srtm/</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">I load 98 rows of data using above.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">So I need elevation data back if I pass to this data a lat and long.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">I initially used query: example<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">SELECT rid, ST_Value(spatial_grid,1,
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> ST_GEOMFROMEWKT('SRID=4326;POINT(-79.9616664245329 40.0000000968475)')<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> ) AS ALTITUDE<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">FROM TERRAIN_GRID;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">This returns the right answer BUT these raster warnings make it difficult to work with:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">NOTICE: Attempting to get pixel value with out of range raster coordinates:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">So I came up with a way to only check the row that the point is actually contained within the row raster first. This eliminates the warnings:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">SELECT ST_Value(spatial_grid,1, ST_GEOMFROMEWKT('SRID=4326;POINT(-79.9616664245329 40.0000000968475)')) AS ALTITUDE<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">FROM TERRAIN_GRID<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">WHERE ST_Contains(ST_Envelope(spatial_grid),ST_SetSRID(ST_MakePoint(-79.9616664245329, 40.0000000968475),4326));<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">So rather than have someone running this query say from python and have to put in lat longs in twice I created a function:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">create or replace function getAltitude(vLongitude decimal,vLatitude decimal)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> returns integer as $$<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">declare<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> lAltitude ssa.TERRAIN_GRID.spatial_grid%TYPE;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> lPointValue varchar := 'SRID=4326;POINT(' || vLongitude || ' ' || vLatitude || ')';<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">begin<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> SELECT ST_Value(spatial_grid,1,
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> ST_GEOMFROMEWKT(lPointValue)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> )
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> INTO lAltitude<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> FROM TERRAIN_GRID<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> WHERE ST_Contains(ST_Envelope(spatial_grid),ST_SetSRID(ST_MakePoint(vLongitude, vLatitude),4326));<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> return lAltitude;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">end;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">$$ LANGUAGE plpgsql;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">This compiles without error, but when I run it, this happens:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">SELECT * FROM getAltitude(-79.96166, 40.0000);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">ERROR: rt_raster_from_hexwkb: Raster HEXWKB input must have an even number of characters<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">CONTEXT: PL/pgSQL function getaltitude(numeric,numeric) line 6 at SQL statement<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">Now it appears to be caused by something in the predicate (where clause):<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">WHERE ST_Contains(ST_Envelope(spatial_grid),ST_SetSRID(ST_MakePoint(vLongitude, vLatitude),4326));<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">I say that because if I change the function to:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">create or replace function getAltitude(vLongitude decimal,vLatitude decimal)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> returns integer as $$<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">declare<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> lAltitude ssa.TERRAIN_GRID.spatial_grid%TYPE;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> lPointValue varchar := 'SRID=4326;POINT(' || vLongitude || ' ' || vLatitude || ')';<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">begin<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> SELECT ST_Value(spatial_grid,1,
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> ST_GEOMFROMEWKT(lPointValue)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> )
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> INTO lAltitude<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> FROM TERRAIN_GRID;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"> return lAltitude;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">end;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">$$ LANGUAGE plpgsql;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">It executes.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0">I cannot find any information on this. Any help on this would be appreciated!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Century Schoolbook",serif;color:#0070C0"><o:p> </o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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