[postgis-users] ERROR: rt_raster_from_hexwkb: Raster HEXWKB input must have an even number of characters

[Regina Obe]

Couple of things

 

1)      No need for ST_Envelope, raster support ST_Intersects against
geometries.

So doing this should be sufficient and should be faster because it can use
the spatial index on the raster, your ST_Envelope won't be able to use the
raster spatial index

 

SELECT ST_Value(spatial_grid,1,
ST_GEOMFROMEWKT('SRID=4326;POINT(-79.9616664245329 40.0000000968475)')) AS
ALTITUDE

FROM TERRAIN_GRID

WHERE ST_Intersects(spatial_grid,ST_SetSRID(ST_MakePoint(-79.9616664245329,
40.0000000968475),4326));

 

2)      I would also rewrite your function as an sql function since it's a
bit shorter and may perform better.  I put in a limit 1 because on occasion,
your point might be in two tiles and you just want one answer back I
presume.

 

create or replace function getAltitude(vLongitude decimal,vLatitude decimal)

            returns integer as $$

               WITH p AS (SELECT ST_SetSRID(ST_MakePoint(vLongitude,
vLatitude),4326) AS IPointValue)

                              SELECT
ST_Value(spatial_grid,1,IPointValue)::integer

                                             FROM TERRAIN_GRID, p ON
(ST_Intersects(spatial_grid, IPointValue) )

              LIMIT 1;

$$ LANGUAGE sql;

 

3)

regarding this issue - ERROR:  rt_raster_from_hexwkb: Raster HEXWKB input
must have an even number of characters

CONTEXT:  PL/pgSQL function getaltitude(numeric,numeric) line 6 at SQL
statement

 

I'm not sure what is causing that.  I suspect you might have a bad raster
tile which perhaps for whatever reason you aren't hitting without the WHERE
clause

Could possibly be a bug in ST_Envelope raster function as well.  I rarely
use ST_Envelope for raster.

 

Can you try the following and see if it triggers the error.  That would
hopefully give you a clue which record is faulty if it is a bad record.

 

SELECT ST_Envelope(spatial_grid)

FROM TERRAIN_GRID;

 

SELECT spatial_grid::geometry

FROM TERRAIN_GRID;

 

 

 

From: postgis-users [mailto:postgis-users-bounces at lists.osgeo.org] On Behalf
Of Michael.CTR.Lazlo at faa.gov
Sent: Friday, August 03, 2018 9:38 AM
To: postgis-users at lists.osgeo.org
Subject: [postgis-users] ERROR: rt_raster_from_hexwkb: Raster HEXWKB input
must have an even number of characters

 

I have created a table loading via raster2psql:

raster2pgsql -a -f Spatial_Grid -F -I -M -T ssa_data -X ssa_data *.tif
ssa.TERRAIN_GRID

 

The tif data comes from http://dwtkns.com/srtm/

 

I load 98 rows of data using above.

 

So I need elevation data back if I pass to this data a lat and long.

I initially used query: example

 

SELECT rid, ST_Value(spatial_grid,1,

                ST_GEOMFROMEWKT('SRID=4326;POINT(-79.9616664245329
40.0000000968475)')

               ) AS ALTITUDE

FROM TERRAIN_GRID;

 

This returns the right answer BUT these raster warnings make it difficult to
work with:

NOTICE:  Attempting to get pixel value with out of range raster coordinates:

 

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:

 

SELECT ST_Value(spatial_grid,1,
ST_GEOMFROMEWKT('SRID=4326;POINT(-79.9616664245329 40.0000000968475)')) AS
ALTITUDE

FROM TERRAIN_GRID

WHERE
ST_Contains(ST_Envelope(spatial_grid),ST_SetSRID(ST_MakePoint(-79.9616664245
329, 40.0000000968475),4326));

 

So rather than have someone running this query say from python and have to
put in lat longs in twice I created a function:

 

create or replace function getAltitude(vLongitude decimal,vLatitude decimal)

            returns integer as $$

declare

            lAltitude ssa.TERRAIN_GRID.spatial_grid%TYPE;

            lPointValue varchar := 'SRID=4326;POINT(' || vLongitude || ' '
|| vLatitude || ')';

begin

            SELECT ST_Value(spatial_grid,1,

                ST_GEOMFROMEWKT(lPointValue)

               )

            INTO lAltitude

            FROM TERRAIN_GRID

    WHERE
ST_Contains(ST_Envelope(spatial_grid),ST_SetSRID(ST_MakePoint(vLongitude,
vLatitude),4326));

            return lAltitude;

end;

$$ LANGUAGE plpgsql;

 

This compiles without error, but when I run it, this happens:

SELECT * FROM getAltitude(-79.96166, 40.0000);

ERROR:  rt_raster_from_hexwkb: Raster HEXWKB input must have an even number
of characters

CONTEXT:  PL/pgSQL function getaltitude(numeric,numeric) line 6 at SQL
statement

 

 

Now it appears to be caused by something in the predicate (where clause):

WHERE
ST_Contains(ST_Envelope(spatial_grid),ST_SetSRID(ST_MakePoint(vLongitude,
vLatitude),4326));

 

I say that because if I change the function to:

create or replace function getAltitude(vLongitude decimal,vLatitude decimal)

            returns integer as $$

declare

            lAltitude ssa.TERRAIN_GRID.spatial_grid%TYPE;

            lPointValue varchar := 'SRID=4326;POINT(' || vLongitude || ' '
|| vLatitude || ')';

begin

            SELECT ST_Value(spatial_grid,1,

                ST_GEOMFROMEWKT(lPointValue)

               )

            INTO lAltitude

            FROM TERRAIN_GRID;

            return lAltitude;

end;

$$ LANGUAGE plpgsql;

 

It executes.

 

I cannot find any information on this. Any help on this would be
appreciated!

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