Surprising default resolution for contour generation

dmcclean
dmcclean Global Mapper UserTrusted User
edited July 2010 in Bug Report
I have a copy of the national elevation dataset, converted into Global Mapper Grid files which are all together in one map catalog. The grids are in geographic lat/long coordinates.

I opened a KML file containing a few lines in New Hampshire which I wanted to map. I also opened the elevation map catalog.

I used the Tools -> Configure menu to change the projection to UTM Zone 19.

I selected "Generate Contours", chose a 500' interval, and an area of interest about 40 miles square. I noticed the contour generation was projected to take an extremely long time (on the order of hours), so I aborted it.

I discovered that the default resolution in the "generate contours" file was unreasonably small in the direction of the y-axis. The x-axis default resolution was (reasonably) 21 meters, but the y-axis default resolution was .15 meters. The elevation data in this area is stored on a 1 arcsecond x 1 arcsecond grid.

I expected the default resolution to roughly match the resolution of the available data, but encountered that it did not.

There may be some reason why better behavior in this case is difficult or impossible, so I'm not sure it qualifies as a bug, but it was unexpected.

Comments

  • global_mapper
    global_mapper Administrator
    edited July 2010
    The default resolution for contour generation should be the resolution of the most detailed loaded elevation layer in both the X and Y directions. You must have had something loaded that was of the resolution listed for that to be used as the default.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com

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