quiver plot for points based on slope direction?

JSLJSL Global Mapper UserPosts: 397Trusted User
edited January 2015 in Vector Data
Hi, I have a set of points that I would like to transform into a quiver plot based upon the magnitude and direction of slope (ex. 10 degrees slope for magnitude, 180 degrees (due south) for direction). However, I can't figure out which, if any, of the attributes that I generate with the "Calculate elevation/slope stat" command corresponds to direction of slope, ex. to the west, southwest, etc.

Thanks for any help.

Comments

  • JSLJSL Global Mapper User Posts: 397Trusted User
    edited January 2015
    I see the SLOPE_DIR attribute in my most recent update--thanks, GM!
  • JSLJSL Global Mapper User Posts: 397Trusted User
    edited January 2015
    Is there perchance any possibility of being able to calculate an average SLOPE_DIR attribute for polygons and lines?
  • JSLJSL Global Mapper User Posts: 397Trusted User
    edited January 2015
    Whoops, just realized lines automatically get bearing attributes. It would be very handy to be able to calculate the average slope direction of a polygon, though...
  • bmg_bobbmg_bob Global Mapper Programmer Posts: 1,873
    edited January 2015
    Just to clarify, are you asking for the average slope direction inside a polygon, similar to the way that average slope is calculated in Calculate Elevation/Slope Stats?

    Cheers,

    Bob
  • JSLJSL Global Mapper User Posts: 397Trusted User
    edited January 2015
    Precisely. It would be very handy to know toward which compass direction a watershed was sloping.

    Thanks...
  • bmg_bobbmg_bob Global Mapper Programmer Posts: 1,873
    edited January 2015
    I have added feature request #15115 to our task list to cover this new functionality. We will post back here when the status of this feature request changes.

    Cheers,

    Bob
  • JSLJSL Global Mapper User Posts: 397Trusted User
    edited January 2015
    Thank you!
  • bmg_mikebmg_mike Global Mapper Guru Posts: 179Trusted User
    edited January 2015
    What you are requesting was already happening in the case that one particular cardinal direction had a majority of the slope aspects, but it wasn't particularly smart. I've improved the logic for finding a dominant aspect so now you will get an ASPECT attribute calculated more often when the bulk of the area faces a particular direction.

    I have placed new builds with the latest changes at the links below:

    32-bit: http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper16.zip
    64-bit: http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper16_64bit.zip

    Simply download the .zip file for the build that you are using and extract over your existing installation files. The likely locations to extract to are as follows:

    32-bit: C:\Program Files (x86)\GlobalMapper16
    64-bit: C:\Program Files\GlobalMapper16_64bit

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • JSLJSL Global Mapper User Posts: 397Trusted User
    edited January 2015
    Thanks, I tried that, and it works with areas that have a unified slope, like a cliff edge, for example. I was wondering if it was possible to find the average slope direction for a larger area that's not so uni-directional, like the plateau below that I've outlined (workspace attached, I used the ETOPO1 DEM from http://www.ngdc.noaa.gov/mgg/global/global.html):

    africa plateau.jpg

    Thanks for the help...
  • bmg_mikebmg_mike Global Mapper Guru Posts: 179Trusted User
    edited January 2015
    I updated the calculation to get the average aspect as well even if there isn't a dominant direction and add an AVG_ASPECT attribute. That one will always be there, whereas ASPECT will only be there when there is a dominant direction.

    I have placed new builds with the latest changes at the links below:

    32-bit: http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper16.zip
    64-bit: http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper16_64bit.zip

    Simply download the .zip file for the build that you are using and extract over your existing installation files. The likely locations to extract to are as follows:

    32-bit: C:\Program Files (x86)\GlobalMapper16
    64-bit: C:\Program Files\GlobalMapper16_64bit

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
    endlesstrail
  • JSLJSL Global Mapper User Posts: 397Trusted User
    edited January 2015
    Thank you very much, but I'm having a problem updating GM. When I copy the 64bit files into my GM 16 folder and try to open, I get the following error:
    2015-01-14_09h48_18.png
    I tried uninstalling and reinstalling GM, but the average aspect attribute didn't show up when I updated measurements and calculated elevation/slope stats. I disabled my antivirus and reloaded the update link you put in your message, copied it into the new GM installation, and still got the same error when I tried to open GM.

    Any suggestions would be very much appreciated--the average aspect is really a valuable calculation to have.
  • bmg_mikebmg_mike Global Mapper Guru Posts: 179Trusted User
    edited January 2015
    Which Program Files folder are you copying to? It sounds like maybe you are extracting the 64-bit files over a 32-bit GM install?

    We also uploaded the v16.1 beta yesterday at http://www.globalmapperforum.com/forums/announcement-news/12200-global-mapper-16-1-beta-now-available.html. It was done right around the time I added the ASPECT update so that may or may not be in there, but it will definitely be in the final release in a week or so.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • JSLJSL Global Mapper User Posts: 397Trusted User
    edited January 2015
    Figured out the problem--I have GM in both my Program Files & my Program Files (x86) folders, and was copying the update to the wrong version. I downloaded the beta and added the updates, and it works! Looking forward to using the aspect attribute--thanks so much for your help.
  • JSLJSL Global Mapper User Posts: 397Trusted User
    edited January 2015
    Just wanted to give an example of how I'm using the aspect attribute:

    I used the contour generator to create areas at the approximate elevation of the plateaus in this region of Africa (hatched areas). I then applied the underlying terrain elevations to the contour area polygons, transforming them from isoheight areas to normal polygons, and calculated the elevation/slope stats. Next, I generated centroids for each area, and transformed them into quiver plots, using the average aspect as the direction vector.

    The results are very interesting for this particular stretch of the Congo River. You can see from the black aspect arrows that most of the plateaus slope in the opposite direction of the flow of the Congo, which is indicated by the red line. This is the reverse of most landscapes, where rivers flow according to the slope of the land.

    aspect.jpg

    Just an example of the neat things that can be done with the aspect attribute...thanks, Mike!
  • @bmg_mike The average aspect is a really helpful addition for something I'm working for groundwater flow. Can that option be used a script? I tested it with one line feature at a time and that works great. But I need to do an average aspect for a 100-200 features at a time. They could either be lines or polygons. I couldn't get the right-click with Calculating Elevation/Slope Statistics for Selected Features to operate on more than one selected line or polygon. I was looking through scripting manual and saw this command : CALC_ELEV_SLOPE_STATS. Can I use that with an option for AVG_ASPECT?
  • bmg_mikebmg_mike Global Mapper Guru Posts: 179Trusted User
    Yes you can use a script like below to add elevation/slope stats to all loaded vector features (or specify a particular layer if you want).

    EDIT_VECTOR CALC_ELEV_SLOPE_STATS=YES

    The Digitizer Tool option to calculate elev/slope stats should work for any number of selected features in the Digitizer Tool. Note that it just adds the attributes to each feature rather than displaying them at the end since there are multiple features. You can see the results with the Feature Info Tool or by showing the Attribute table.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    http://www.bluemarblegeo.com/
Sign In or Register to comment.