Cloud imagery
redesigner
Global Mapper User
Hi! I've been trying to load some data of Suomi NPP in global mapper (hdf5-format from CLASS). I'd like to have some very highres greyscale-imagery of clouds, but I don't know how to interpret the data and which bands to use. The images seem to be not georeferenced and correctly projected. I'm not very experienced with satellite-data, is there any other way to get highres cloud maps that cover the whole planet with at least 0,5km per pixel?
Best regards
Tobi
Best regards
Tobi
Comments
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Tobi,
Which version of Global Mapper are you using? The absolute latest builds support more bands of the VIIRS data, which I'm guessing is what you are using. It is a bit of a pain to tease useful data out of these though. I would first suggest getting the latest build and see if that is easier to use. I have placed a new build at http://www.globalmapper.com/global_mapper13.zip with the change for you to try. Simply download that file and extract the contents into your existing v13.xx installation folder to give it a try. If you are using the 64-bit v13 version there is a new build at http://www.globalmapper.com/global_mapper13_64bit.zip .
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Hi Mike,
thanks for your answer! I've downloaded the latest build, but it's still weird. I've attached a screenshot of the loaded overlay, it seems to be squashed and (also when I use an hdf5-viewer) the images are splitted in 4 rows.
Best regards
Tobi
Screenshot - 30.07.jpg -
The squash could be just the projection you are viewing in. Try switching to a projection with less distortion on the Projection tab of the Configuration dialog, maybe UTM if you just need a limited area or something like Robinson for larger areas of the earth and see if that helps.
For the striping, that seems to be what is actually stored in the raw data files, not really sure what to do about that without somehow manipulating the raw data. Most of what is out there from these satellites is just raw sensor data that hasn't been processed into a nice visual product yet.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
I see, i thought they put enough information inside these raw-files to map them correctly.
The projection I am using is Plate Carree, you can see in the attached screenshot, that the image should be projected like the image from the world imagery.
Screenshot - 31.07.jpg -
Is the image supposed to cover exactly the same area as the imagery? It is hard to tell when cloud data is aligned properly since it doesn't necessarily align with any ground features. How can you tell when it is correct?
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
You can see the persian gulf reflecting the sunlight (so the selected band doesn't seems to be a cloudmap..):
Screenshot - 31.07-02.jpg -
Ah yep I can see that, it does look like there is some incorrect positioning, the HDF5 data was always very odd with how they positioned stuff. Is it possible for you to FTP the file(s) that you are working with so I can take a look and try and get them aligned properly? You can FTP them to ftp.globalmapper.com using a username of 'upload@globalmapper.com' and a password of 'upload'.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Hi Mike,
first of all, thank you very much for this outstanding support! I wish Autodesk could see that...
I've uploaded a .h5-file (almost 3GB, which took a while). I've downloaded the data from http://www.nsof.class.noaa.gov
Tobi -
FYI I'm downloading the file, it is quite large though and I'm on the road, so it will be tomorrow at least before I have the entire file and can take a look.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Tobi,
I have a likely fix for this. I found that the lat/lon bounding coordinates were being truncated to whole numbers of degrees, so each boundary was shifted by up to 1 degree. I have that fixed now so the full resolution of the bounds should be maintained. I have placed a new build at http://www.globalmapper.com/global_mapper13.zip with the change for you to try. Simply download that file and extract the contents into your existing v13.xx installation folder to give it a try. If you are using the 64-bit v13 version there is a new build at http://www.globalmapper.com/global_mapper13_64bit.zip .
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Thanks a lot mike! But I still have the same problem as before. I've also attached a screenshot with 5 of these (i guess serial) files loaded. I have no idea, but i guess the tops and bottoms of each pic should touch, due to the longitudinal orbiting of the satellite?
Screenshot - 03.08.jpgScreenshot - 03.08_full.jpg
Cheers,
Tobi -
I've found a document at http://jointmission.gsfc.nasa.gov/science/sciencedocuments/052012/CDFCB/474-00001-04-02_JPSS-CDFCB-X-Vol-IV-Part-2_0122A_20120322.pdf that seems to describe more of the VIIRS data. I will go through that and see if I can fix the rest of the positioning issues.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com
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