add algorithm for scaled reflectance encoding

[janzandr]

Discussed with @jakimowb.

After importing satellite data into the EnMAP-Box, reflectance data is scaled between 0 and 1. Exporting this data into GTiff or ENVI file, would result in floating-point data. It is proposed to implement an algorithm for storing a raster using an integer data type using scaled reflectance encoding (e.g. multiply the data by 10000 and cast it to Int16).

The following parameters are describing a scaled reflectance encoding:

• [ ] input range (e.g. 0 to 1 as default)
• [ ] output range (e.g. 0 to 10000 as default)
• [ ] data type ( Int16, Byte

[jakimowb]

It would be nice that saving such scaled data does preserve the original data types used. E.g. if data is int + scaling, the export algorithm should try the same.

[janzandr]

With "export algorithm" you mean the "Save raster layer as" / "Translate raster layer" algo?

[jakimowb]

Yes.

[janzandr]

Both algos use gdal_translate, which preserves the data type and the scaling factor.

[janzandr]

BUT, if you are using any other algo for processing the data, the data is read by QGIS API, which will scale the data on-the-fly.

[jakimowb]

After importing satellite data into the EnMAP-Box, reflectance data is scaled between 0 and 1 Probably not the scope of this issue, but do our import algos perform a "hard scale", i.e. writing double instead ints?

[janzandr]

After importing satellite data into the EnMAP-Box, reflectance data is scaled between 0 and 1 Probably not the scope of this issue, but do our import algos perform a "hard scale", i.e. writing double instead ints?

No, the data is stored as ints with scaling factors. USING the data in QGIS will on-the-fly scale the data into 0 to 1 floats.