Opening Data Files

Opening Data Files#

WISER reads several raster formats natively and can fall back to any format GDAL supports. Most of the time you can pick a file and WISER works out the rest.

This page covers the cases where it is worth being deliberate — because the file type you choose in the Open dialog matters, and so does which file you pick when a dataset is spread across more than one.

The file type you choose matters#

The file type dropdown at the bottom of the Open dialog is not only a way of hiding files you are not interested in. It also tells WISER what the file is.

  • Leaving it on All supported files asks WISER to work the format out for itself. This is the right choice almost always.

  • Choosing a specific type — “ENVI raster files”, “NetCDF raster files”, “PDS3 raster files”, and so on — tells WISER to open the file as that format and nothing else.

Why this matters#

Some files can be read by more than one format. A .img file might be an ENVI raster or a PDS3 product; an .xml file might be a PDS4 label or something else entirely. WISER inspects the contents rather than trusting the extension, and it is right the overwhelming majority of the time.

But when a file is genuinely ambiguous — or when it is unusual enough that automatic detection picks a format that reads it, just not the way you want — picking the type explicitly settles it.

Tip

If a file opens but the data looks wrong — wrong number of bands, missing wavelengths, unexpected scaling — try opening it again with the file type set explicitly. Automatic detection may have chosen a format that can read the file but does not understand all of its metadata.

Forcing a type will report failure rather than guess again#

Choosing a specific file type is treated as a statement of fact. If WISER cannot read the file as that format, it reports an error rather than quietly trying something else.

That is deliberate: if you have said a file is NetCDF and it is not, having it silently open as something else would hide the problem rather than tell you about it. Switch back to All supported files to let WISER decide.

Which file to pick for multi-file datasets#

Several formats store one dataset across more than one file. You may select either the header or the data file — WISER finds the other.

ENVI#

An ENVI dataset is a header (.hdr) plus a data file, which may have no extension at all, or .img, or .dat:

scene.hdr     <- the header
scene.dat     <- the data (or "scene", or "scene.img")

Select either one. Both files must sit in the same directory and share a name; WISER cannot open the header on its own.

Note

If you have an ENVI header whose data file is missing or has been renamed to something unexpected, WISER reports which filenames it looked for. Renaming the data file to match the header — same name, one of the extensions above — is usually enough to fix it.

GeoTIFF#

A GeoTIFF is normally a single .tif or .tiff file. Some are accompanied by a .tfw world file carrying the georeferencing. Select either the image or the world file.

PDS#

PDS3 products may have a detached label (.lbl) beside the data, or an attached label inside a single .img. Select the label when there is one. PDS4 products use an .xml label — select that.

Formats WISER opens#

Format

Typical files

ENVI raster

*.img, *.hdr, *.dat, or no extension

TIFF / GeoTIFF

*.tif, *.tiff, *.tfw

NetCDF

*.nc

JPEG 2000

*.JP2

PDS3

*.PDS, *.img, *.lbl

PDS4

*.xml

FITS

*.fits, *.fit, *.fts

ASCII Grid

*.asc

ENVI spectral library

*.sli, *.hdr

Anything else GDAL reads

HDF4/5, GRIB, COG, and more

If your file is not in this list, try Try luck with GDAL in the file-type dropdown. GDAL supports a great many formats beyond those WISER handles specially, and this option asks it to open the file with whatever driver fits. Data loaded this way may carry less metadata — wavelengths and band names in particular — than a natively supported format.

Files containing several datasets#

Some files hold more than one dataset. A NetCDF file, for example, may contain several variables, each a separate raster.

When you open such a file, WISER asks which one you want before loading. Pick the sub-dataset you are interested in and it is loaded as its own dataset in the session.

If you save your session as a project, the specific sub-dataset you chose is recorded, so reopening the project restores exactly what you had rather than asking again.

Troubleshooting#

“Couldn’t load file … unsupported format”

No format WISER knows could read the file. Check the file is complete and not truncated. For ENVI data, check its .hdr is present and beside it. As a last resort try Try luck with GDAL.

“Can’t find the raster file corresponding to …”

You selected an ENVI header or a .tfw world file, but the matching data file is not beside it. The message lists the filenames WISER looked for.

The file opens, but as the wrong kind of data

Open it again with the file type set explicitly instead of All supported files.

A file that used to open no longer does

Check whether files have been added or renamed alongside it. A stray header file with the same base name as an unrelated raster can change how a directory is interpreted.