Cropping viewshed boudary
Francesca Rowson
Global Mapper User
Can anyone help me please? I am a complete novice on global mapper and I have a deadline on monday.
The extent of my view shed extends beyond the extent of my data so I need to crop it to the edges of the area. I have tried drawing a new area feature around the extent of my data and selected 'crop to currently selected polygons' however this has not worked, nothing happens.
Any other ideas?
The extent of my view shed extends beyond the extent of my data so I need to crop it to the edges of the area. I have tried drawing a new area feature around the extent of my data and selected 'crop to currently selected polygons' however this has not worked, nothing happens.
Any other ideas?
Comments
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When are you doing the crop? You should be able to select the area to crop to, then when you do an export select the option to crop to the selected area(s) on the Export Bounds tab. If you are cropping in the Options tab for the layer note that will just crop the raster coverage of the view shed. If you have any view shed coverage areas they would not be cropped by that, but can be cropped directly using the Crop right-click menu in the Digitizer Tool.
Thanks,
Mike
Global Mapper Guru
geohelp@bluemarblegeo.com
Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation -
I was trying to crop while I was still working on the work space. I just tried both of your suggestions but neither of them worked. When I export the file as a pdf the view shed outside of the area I selected to crop to is still visible.
Is there a way set adjust the view shed analysis so that it only highlights areas within the boundaries of my data? rather than trying to crop it after.
Thank you Mike -
Did you also have the option checked to fill the page on the PDF export? That could cause the data to not crop.
If you want your view shed cropped to start with then you can crop your terrain surface to your area of interest prior to calculating the view shed on the Cropping tab of the Options dialog for the terrain surface. Then the view shed should stop there since it has no terrain to use.
Thanks,
Mike
Global Mapper Guru
geohelp@bluemarblegeo.com
Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation -
Hi Mike, regarding this latter suggestion of cropping the terrain, it seemed like a good idea until we tried it and found that, if the view shed would have been visible to an area of zero height beyond the terrain, it is still calculated and displayed. In the image below, the terrain has been exported (cropped to a 20km range ring) and re-imported, then the original larger terrain layer closed. Then a viewshed is created (with 20km range) around 10km north of the terrain centre. The the resulting viewshed area outside the circle of cropped terrain has no other height reference data. Also, it isn't possible to delete the coverage area due to the nature of the viewshed object - it remains visible (probably the image part of the viewshed?)
2013-08-19_16-29-41.jpg
So provided your viewshed would not be seen on areas of zero elevation, it will work, but more often, probably not. Is there a way to truly limit the viewshed to only use terrain data? -
I have added a checkbox option to control whether or not missing elevation samples within the range area treated as zero (the current default) or not. I have placed a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v14.xx installation folder to give it a try. If you are using the 64-bit v14 version there is a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14_64bit.zip .
Thanks,
Mike
Global Mapper Guru
geohelp@bluemarblegeo.com
Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation -
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