GDAL Warp Using QGIS from AK_IFR to EPSG:4326 looks odd

gdalgdalwarpqgis

I am using QGIS for converting tiff from AK_IFR to EPSG:4326 (CRS), but in QGIS tiff looking perfect

but while exporting it looks like this

Source Image Details: FAA IFR Chart

Extent -3738773.4199999999254942,-194349.8061717178206891
: 819446.2539994539692998,1674273.9499999999534339

Width 24613
Height 10090

Data type
Byte – Eight bit unsigned integer
GDAL Driver Description GTiff
GDAL Driver Metadata GeoTIFF

Dataset Description
Band 1
STATISTICS_APPROXIMATE=YES
STATISTICS_MAXIMUM=255
STATISTICS_MEAN=180.24847437723
STATISTICS_MINIMUM=0
STATISTICS_STDDEV=112.31675006634
STATISTICS_VALID_PERCENT=100
Band 2
STATISTICS_APPROXIMATE=YES
STATISTICS_MAXIMUM=255
STATISTICS_MEAN=180.23919541579
STATISTICS_MINIMUM=0
STATISTICS_STDDEV=111.97269231222
STATISTICS_VALID_PERCENT=100
Band 3
STATISTICS_APPROXIMATE=YES
STATISTICS_MAXIMUM=255
STATISTICS_MEAN=180.3117834084
STATISTICS_MINIMUM=0
STATISTICS_STDDEV=111.73696572256
STATISTICS_VALID_PERCENT=100

More information
Dimensions X: 24613 Y: 10090 Bands: 3
Origin -3.73877e+06,1.67427e+06
Pixel Size 185.1956150814388309,-185.1956150814388309

Coordinate Reference System (CRS)
Name: AK_IFR
Units: meters
Method: Lambert Conformal Conic
Celestial body Earth
Reference: Static (relies on a datum which is plate-fixed)

Best Answer

The map goes over the dateline: West_Bounding_Coordinate: 148.175845, East_Bounding_Coordinate: -138.964596. QGIS shows EPSG:4326 map in range from -180 to 180 degrees and therefore the map gets splitted in two halves. The result is correct even it does look odd.

This command prevents the split but eastern side will have longitudes which are larger than 180.

gdalwarp -t_srs epsg:4326 ENR_AKH02.tif enr_4326_180.tif --config CENTER_LONG 180
Creating output file that is 26203P x 9758L.
Processing ENR_AKH02.tif [1/1] : 0...10...20...30...40...50...60...70...80...90...100 - done.

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[GIS] Rasterize shapefile to a new gtiff file with gdal_rasterize utility,however,I cannot open the tif file

Three suggestions:

Try outputting to another format. Maybe Jpeg or PNG. These will likely work better with Windows Photo Viewer.
Download IrfanView. This will display your tiff quite well.
If neither work - could you run 'gdalinfo -stats Countries02.tif' and post the output.

Edit:

The output is float64. This is likely the issue. Try 'gdal_translate -ot Byte -scale Countries02.tif Countires02_scaled.tif'

I'm not sure why rasterize is creating 64-bit output, but not much reads 64-bit. Also, -scale should not be necessary, but is precautionary.

[GIS] Cutting out depth information in raster. Calculating volume in Qgis

I believe you can use some map algebra (raster > raster calculator) before you can preform your volume measurements in grass.

Assuming that your bathymetric data use positive values to represent the sea depth, and using your example for the range as 50 the min_depth and 200 the max_depth. For each of the raster cells you need to "remove" anything below the 200 and above the 50. You have 3 possible situations:

your cell depth is higher than the max_depth

(@bathymetry > 200)
your cell depth in the min_depth - max_depth range

(@bathymetry <= 200) * (@bathymetry >= 50)
your cell depth is lower that your min_depth

(@bathymetry < 50)

In case 1 the size of the water column will be the entire size of our range:

(@bathymetry > 200.0) * (200.0 - 50.0)

In case 2 the "water column" is from your bathimetry depth until the minimum value of the range:

(@bathymetry <= 200.0) * (@bathymetry > 50.0)*(@bathymetry - 50.0)

In case 3 there is no useful "water column" for your specie therefore it would be:

(@bathymetry <= 50)*0.0

Since the 3 cases never occurs at the same time, all we need is to sum the expressions:

(@bathymetry > 200.0) * (200.0 - 50.0) + (@bathymetry <= 200.0) * (@bathymetry > 50.0)*(@bathymetry - 50.0) + (@bathymetry <= 50)*0.0

Since the last expression is always zero, the is no point in including it:

(@bathymetry > 200.0) * (200.0 - 50.0) + (@bathymetry <= 200.0) * (@bathymetry > 50.0)*(@bathymetry - 50.0)

And the generic version of the expression would be:

(@bathymetry > max_depth) * (max_depth - min_depth) + (@bathymetry <= max_depth) * (@bathymetry > min_depth)*(@bathymetry - min_depth)

After this, you can use the output raster in r.volume to sum all "water columns" values

Best Answer

Related Solutions

[GIS] Rasterize shapefile to a new gtiff file with gdal_rasterize utility,however,I cannot open the tif file

[GIS] Cutting out depth information in raster. Calculating volume in Qgis

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