[GIS] Wrong Min and Max Pixel values

pixelqgis

I want to convert a raster .tif file into a raster .asc file in QGIS. For this, I am selecting Raster -> Conversion -> Translate option. I am getting the output .asc file.

But, both the minimum and maximum pixel values of this raster file is displayed as 1.79769e+308 and I am not able to see any data in this output file.

It is true that there is no data available in this raster file. But, even in that case, the minimum and maximum pixel values will not be like this.

Unfortuantely, I am getting very crazy pixel values : Min = 1.79769e+308 and Max = 1.79769e+308.

Whenever I do any type of geoprocessing in QGIS with a raster which has no data / feature, I am getting the pixel values as Min = 1.79769e+308 and Max = 1.79769e+308.

What is the exact reason for this issue and how can I solve this ?

Best Answer

Another possibility is that you are working on renamed layers. When I did raster calculations I often got faulty layers (1.79769e+308 values) generated in QGIS 3x, without any error. I tested on QGIS 3.2 and 3.4.3.

There is a raster calculator bug caused by renaming of layers that only was completely fixed on 2019-01-02. See issue 20601, it is fixed, but has yet to make it to a stable build. As a workaround, in 3.4.3, the Gdal raster calculator in the Processing Toolbox seems to work, as is the one in the main menu "Raster - Raster Calculator"

Related Solutions

[GIS] Getting multiband raster’s min and max values with Python in QGIS

Next code works with multi band raster. It uses QgsRasterDataProvider objects to calculate statistic through QgsRasterBandStats objects.

layer = iface.activeLayer()

extent = layer.extent()

provider = layer.dataProvider()

for band in range(1, layer.bandCount() + 1):
    stats = provider.bandStatistics(band, QgsRasterBandStats.All, extent, 0)
    min = stats.minimumValue
    max = stats.maximumValue
    print 'min: {:.2f}, max: {:.2f}'.format(min, max)

After running the code with RGB raster of next image:

I got printed, at Python Console of QGIS, next values:

min: 62.00, max: 255.00
min: 89.00, max: 255.00
min: 90.00, max: 255.00

They are identical to reported in Metadata Layer Properties.

[GIS] QGIS 3.4 – Rasterize creates layers with 1.79769e+ 308 min/max values

The problem is in the definition of the extents of the output raster.

When using an input layer with a Coordinate Reference System, but defining the extension of the output raster through a layer with a different CRS, the Rasterize tool creates a raster with the CRS of the input layer, but with the coordinates of its extents referred to the other system.

As a result, nothing that was in the input layer is found in those coordinates and the output raster contains only nodata values.

The solution is to use both layers defined under the same CRS (reprojecting some of them), when it is intended to Raterize a layer with the extents defined by another layer.

Best Answer

Related Solutions

[GIS] Getting multiband raster’s min and max values with Python in QGIS

[GIS] QGIS 3.4 – Rasterize creates layers with 1.79769e+ 308 min/max values

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