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Thread: CLASS .ASC File to ArcGIS Issue

  1. #1
    Chad Mahoney
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    Default CLASS .ASC File to ArcGIS Issue

    I have be assigned a task of find quality Atmospheric Data to use in our research. I am exploring some different sources. I have come across the CLASS Ozone data. The format is .asc but I am unable to get the file into ArcGIS. I am not familiar with this type of ASCII data. If anyone could give me a bit of advice on what way to go about to import this file into ArcGIS. I cannot attach the .asc file as it exceeds the file size limit of the forum. If you want to view I can email the file.


    Thanks in Advance

    Chad
    Chad Mahoney
    GIS Specialist
    Green Power Labs Inc.

  2. #2
    Donovan Cameron

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    Default Re: CLASS .ASC File to ArcGIS Issue

    Chad,

    ArcGIS includes support for converting ASCii files. Adding an ASCii/txt table to arcmap.

    Often, the output is a point file with values attached that can then be used for interpolation. This sounds like what you have in your case.

    It may be safe to use ASCII to Raster for a direct interpolation to a raster dataset.

    I would recommend bringing the table into arcmap (or other software, maybe Access for such a large file) first to see if you can visualize the table to see if the points are floating or integer so you can set up your parameters in the ASCII to Raster tool.


  3. #3
    William Huber

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    Default Re: CLASS .ASC File to ArcGIS Issue

    The NOAA has a FAQ on this subject at http://www.class.ncdc.noaa.gov/notification/faq.htm#11 .
    --Bill Huber
    Quantitative Decisions
    For more help, visit the worldwide community at http://gis.stackexchange.com

  4. #4
    Chad Mahoney
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    Default Re: CLASS .ASC File to ArcGIS Issue

    Bill, Thanks for the link to the NOAA site, I am going to read thorough that now.

    Donovan, I have tried to import using the ASCII to Raster, but I get a grid error. I believe that the ASCII file is different from what is needed for an Arc ASCII file. I attached part of the ASCII, if you look at the file compared to an ASCII file that will import into Arc the first thing that I see that is different is the lat = that is not in a regular ASCII files. I am thinking that this could be the problem.

    The file is not the full file as the size is over the forum size limit.
    Attached Files

  5. #5
    William Huber

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    Default Re: CLASS .ASC File to ArcGIS Issue

    Yes, Chad, this is a "raw" file. It has to be unpacked with specialized software. I wasn't (during my brief search) able to turn up technical documentation about the format. Regardless, the coding would not be at all difficult; my hope is that the NOAA site might direct you towards existing solutions and that perhaps registered users have more access to such material.
    --Bill Huber
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    For more help, visit the worldwide community at http://gis.stackexchange.com

  6. #6
    Chad Mahoney
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    Default Re: CLASS .ASC File to ArcGIS Issue

    Yes, I have gone over the NOAA site but haven't found much info either. I have submitted the questions to the CLASS Help and waiting on a response. I have noticed that some of the data on the site comes in NetCDF format, but not Ozone. I will continue to go through the site to hopefully find some help about the processing the raw .asc file with other software..Thanks for the help Bill hopefully I can find the correct software on the site.
    Chad Mahoney
    GIS Specialist
    Green Power Labs Inc.

  7. #7
    Donovan Cameron

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    Default Re: CLASS .ASC File to ArcGIS Issue

    Quote Originally Posted by MahoneyChad View Post
    ...some of the data on the site comes in NetCDF format, but not Ozone. I will continue to go through the site to hopefully find some help about the processing the raw .asc file with other software...
    I have found some links that may be of interest, and I think your response back from the CLASS help is going to be the end all.

    But for future reference (I don't even know if these relate to what you are looking to do):

    Unidata and in the Data Flow, it shows that if your data is in ASC/TXT, then you may be using McIdas-X

    For using NNDC data, there is a link at the bottom for an email and some other reports that may take you somewhere...

    Example PDF from regarding NOAA data uses (this is a student example) but it uses ASCII to Raster...

    Marine Geospatial Ecology Tools also convert from NDF to a usable GIS format. This focuses mostly on the HYCOM dataset in HDF format.



    When you do discover the process, can you post here?


  8. #8
    Chad Mahoney
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    Default Re: CLASS .ASC File to ArcGIS Issue

    These links have some great information thanks for posting!

    I will look deeply into McIDAS now that you have pointed that out. I was directed there for possible satellite data for Europe, but have not yet had the time to look into that possibility.

    I have the Marine Geospatial Ecology Tools installed and worked with them today for the first time. Works great for creating a raster from NDF data.

    As for the HDF data, I am also working with NASA's atmospheric composition data which is mostly HDF format but have had little luck as it only works with .he4 where as NASA uses mostly .he5. I am currently looking for a HDF editor, because the .he4 data has 2 swaths with the exact data file names and the toolset cannot work with multiple data file names. HDFView states it allows read/write for renaming but the HDF file may have protection to not allow renaming as I cannot rename.

    I will be sure to post once I have discovered the process. As well as if I solve the HDF issue I am also facing.

    Thanks for all the help this far.

  9. #9
    Chad Mahoney
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    Default Re: CLASS .ASC File to ArcGIS Issue

    I have not had much luck with this. The first reply from CLASS help desk stated that I have having issues because the file is ASCII format but provided another contact. I did contact someone who provided a bit more insight. Stating that I would have to convert text file from UNIX to Windows format and then apply a header, but was not sure if the file would be able to be used in ESRI's products. I have been busy and have yet to try this.
    I did however come across this data from NASA which I am currently working with http://neo.sci.gsfc.nasa.gov/Search.html . The downloadable formats include GeoTIFF, JPEG, KMZ and CSV. This seems to have the data layers I was looking for as well as much more.

  10. #10
    William Huber

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    Default Re: CLASS .ASC File to ArcGIS Issue

    The ASCII format is not the problem. The header is simple enough to replace. The difficulty is that the data appear to be blocked and without delimiters. Thus you need to know the field length in bytes, the order in which the data are laid down, and what code(s) are used for missing data. You can reverse-engineer this easily enough. However, some kind of conversion will be needed before any of the ArcGIS importers will work with it.
    --Bill Huber
    Quantitative Decisions
    For more help, visit the worldwide community at http://gis.stackexchange.com

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