[gdal-dev] Multifile ArcGrid Issue

[Dan Lewis]

Hi,

I'm trying to pull elevation data from the GMTED2010 Global Grids, which
are distributed as ESRI ArcGrids (
http://topotools.cr.usgs.gov/GMTED_viewer/gmted2010_global_grids.php).

Here's a minimal program that illustrates my problem:

int main()
{
    GDALDataset  *poDataset;

    GDALAllRegister();

    //poDataset = (GDALDataset *) GDALOpen(
"C:/data/GMTED2010/mn30_grd/mn30_grd/w001000.adf", GA_ReadOnly );
    poDataset = (GDALDataset *) GDALOpen(
"C:/data/GMTED2010/mn15_grd/mn15_grd/w001000.adf", GA_ReadOnly );

    double adfGeoTransform[6];
    poDataset->GetGeoTransform( adfGeoTransform );

    double latitude = 34.52798, longitude = -112.875733;
    //double latitude = 67, longitude = -141;

    double x = (longitude - adfGeoTransform[0]) / adfGeoTransform[1];
    double y = (latitude - adfGeoTransform[3]) / adfGeoTransform[5];

    float val;
    poDataset->RasterIO( GF_Read, x, y, 1, 1,
                      &val, 1, 1, GDT_Float32,
                      1, NULL, 0, 0, 0 );
    std::cout<<"Check elevation at point ("<<x<<", "<<y<<"): "<<val<<"\n";

    return 0;
}

I get the following errors:

ERROR 1: Illegal block requested.
ERROR 1: IReadBlock failed at X offset 62, Y offset 742
ERROR 1: GetBlockRef failed at X block offset 62, Y block offset 742

It works as expected if I pull from locations earlier in the file (64,
-141) or if I use a lower resolution file (mn30_grd).

I found an old ticket (#1198) that seems related but has been marked as
fixed.

Any ideas?

Thanks,

Daniel
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