Global Mapper v25.0

Contours from Irregular Data Area?

Roger Edrinn
Roger Edrinn Global Mapper UserTrusted User
edited April 2011 in Elevation Data
I need to Generate Contours from an Irregular Data Area. Easy enough to set up a gridded output, but grids are rectangular, my data is a trapezoid. What will happen when GM sees the empty data area?

Also, need to stop multiple times, likely to take a week or more. GM has a command switch to ignore existing files. Can I just click cancel and when I restart the GM script, it will pick up where it left off?

Thanks

Comments

  • global_mapper
    global_mapper Administrator
    edited April 2011
    The empty data area is fine, you just won't get any contours in that area.

    If you skip existing files then you can easily restart a cancelled operation. It should pick up where you left off.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Roger Edrinn
    Roger Edrinn Global Mapper User Trusted User
    edited April 2011
    Works as advertised, started up the morning and it adding new contour package files at the end of the stack. Loaded adjacent contours from different days, perfect match. Question and a comment.

    Why does GM take ~3-min per R/C segment when there is no DEM data to load. Seems as if GM would recognize the lack of data and move to the next R/C segment in a few seconds.

    If the path is long, then the file name being processed is truncated by the small main dialog. Is there a way to always show the file name and shorten the path?

    Thanks
  • global_mapper
    global_mapper Administrator
    edited April 2011
    What do your R/C segments look like? Do you have the 'Fill Small Gaps' option checked? If so this can slow things down a lot in large areas with no data in them so you will likely want to uncheck that option.

    Which small main dialog are you seeing the filename truncated in?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Roger Edrinn
    Roger Edrinn Global Mapper User Trusted User
    edited April 2011
    What do your R/C segments look like? Do you have the 'Fill Small Gaps' option checked? If so this can slow things down a lot in large areas with no data in them so you will likely want to uncheck that option.
    Yes, thanks for that suggestion.
    Which small main dialog are you seeing the filename truncated in?
    There are three small dialogs:
    1. The first shows the progress of the entire process. This one has the current file being processed and that file name is clipped.
    2. The second (Finding contour segments), same size, shows the progress of the current process, it has no file name
    3. The third only shows for a few seconds and is the saving of the package file.

    Thanks
  • global_mapper
    global_mapper Administrator
    edited April 2011
    I updated the one dialog to just show the filename and not the full path as well so you should be able to see it all. I have placed a new build at http://www.globalmapper.com/global_mapper12.zip with the change for you to try. Simply download that file and extract the contents into your existing v12.xx installation folder to give it a try. If you are using the 64-bit v12 version there is a new build at http://www.globalmapper.com/global_mapper12_64bit.zip .

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Roger Edrinn
    Roger Edrinn Global Mapper User Trusted User
    edited April 2011
    I canceled the process and started over, checking the skip existing files box.
    What do your R/C segments look like? Do you have the 'Fill Small Gaps' option checked? If so this can slow things down a lot in large areas with no data in them so you will likely want to uncheck that option.
    Here's what happened with "small gaps" unchecked.

    In areas with DEMs but just ocean, it took ~2 min per R/C segment. In grid areas with no DEMs, GM took ~10 sec per R/C segment to move to the next.

    I'd like to suggest you create a small dummy data-less file, that way when the next contour run occurs, GM will automatically skip those named files. Clearly not a high priority, but something for your infinite to do list.

    Thanks for the help.
  • global_mapper
    global_mapper Administrator
    edited April 2011
    The whole point of the 'fill small gaps' option is to allow areas of no data to be filled using surrounded valid data, so creating a dummy data-less file with valid data in those locations would defeat that functionality. If you don't want to fill gaps (typically you don't), just uncheck that option and it should go much faster.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Roger Edrinn
    Roger Edrinn Global Mapper User Trusted User
    edited April 2011
    The whole point of the 'fill small gaps' option is to allow areas of no data to be filled using surrounded valid data, so creating a dummy data-less file with valid data in those locations would defeat that functionality. If you don't want to fill gaps (typically you don't), just uncheck that option and it should go much faster.
    Seems you missed the point of my suggestion. The "fill small gaps" is not the issue, rather skip existing files is the issue.

    Once GM has gone through a data-less area quickly using the uncheck "fill small gaps", then if GM would create a "dummy" file at each R/C node where there are no contours, then GM would NOT have redo that same R/C node each time the process is restarted. Does not GM use the file name to know what to skip?

    Does that make sense?

    Thanks
  • global_mapper
    global_mapper Administrator
    edited April 2011
    Oh I see what you are saying, yes the filename is what is used to skip existing files, although typically users don't want an empty file that they have to delete later created, so while it would speed up canceling and restarting operation, you would then have some cleanup to do at the end to get rid of the useless empty files, so there is a tradeoff and the cleanup is more error prone.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • Roger Edrinn
    Roger Edrinn Global Mapper User Trusted User
    edited April 2011
    I wouldn't delete the empty files. My plan is to create a contour catalog, all 800 files, of the entire folder, with contours or empty. From my experience GM is smart enough to live with empty files in a catalog.

    That catalog would then become one of many layers and the whole ensemble is then gridded to MP text files. That's my process. Don't see how empty contour files create a problem.

    Of course I can't speak for the variety of GM users, you're the only one to make that call.

    So my suggestion is a switch, next to the skip switch, "Create empty files for no contours" Useful for large water areas.

    Thanks
  • Nicolasa77
    Nicolasa77 Global Mapper User
    edited April 2011
    Ive tried and tested this tool post reading the post. Its really a nice one. I liked the keyword winner!



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