[Shake-dev] Orientation of the shake_result.hdf IMTS grids?

[timbeale at catalyst.net.nz]

Hi,

I'm trying to read the shakemap imts data directly from a 
shake_result.hdf file and I'm just a little unsure what lat/long 
co-ordinates the 0,0 dataset index refers to. I.e. does the dataset 
start from upper-left or lower-left or something else?

I'm trying to read a grid dataset like this:

DATASET "/arrays/imts/GREATER_OF_TWO_HORIZONTAL/PGA/mean" {
    DATATYPE  H5T_IEEE_F64LE
    DATASPACE  SIMPLE { ( 217, 303 ) / ( 217, 303 ) }
    DATA {
    (0,0): -5.84422, -5.83708, -5.82995, -5.82284, -5.81574, -5.80865,
...

I can see the metadata attributes for xmin, xmax, ymin, ymax, which tell 
me the lat/long grid that the dataset is in. But what lat/long 
co-ordinates does dataset index 0,0 correspond to - is it xmin, ymin? I 
saw some references to 'upper left' (i.e. xmin, ymax) in the python code 
(e.g. geodict.py getRowCol()) which confused me.

Unfortunately I need to work in another language, so I can't use the 
MapIO python code to read the file. I tried to read through the Python 
code to work this out, but I got a little lost.

If someone could confirm where the dataset index starts from, that would 
be a big help.

Thanks,
Tim