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Hi, I have got a 11 large rasters and each raster overlaps with at least one adjacent raster. The rasters are orthomosaics that were generated from a UAV. The problem I am having is that along the boundaries of these rasters the quality isn't the greatest, so I need to clip these areas out of the raster while maintaining at least a little bit of overlap between adjacent rasters. I've attached an image to clarify what I mean. My original plan was to create a polygon around each raster so it only encompasses the areas of higher quality and then clipping to the extent of the polygon. However, I'm finding this to be rather time consuming. I am constantly having to edit the extent of the polygons and comparing them with the adjacent rasters to ensure I don't clip too much. I'd like to know if there is an easy way to find the overlap between each of the rasters and then use that to at least help clip out the areas with poor quality.
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02-05-2016
07:51 AM
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Thanks a lot for you input. It's greatly appreciated! Cheers, John
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04-17-2015
10:37 AM
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The coordinate system defaults to unknown And the extent values are shown below. This may be an issue with the processing of the scan data. It looks like I may have to go back a couple of steps and attempt to assign a coordinate system to the raw data.
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04-17-2015
10:15 AM
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The lidar data was originally a point cloud that I exported as a .pts file from Cyclone. It was basically xyz format using meters. I don't know if it actually had a defined coordinate system. I did not use UTM Zone 12 for the las dataset. I can't seem to give it a projection since it doesn't appear as an option when I use the project tools in arcmap. The I made the coordinate system GCS_WGS_1984 in the las dataset from the properties dialog in arccatalog. But it didn't really seem to affect the las file within the dataset. I now see that the spatial reference is probably the main issue here, but I'm not sure on how the problem can be addressed.
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04-17-2015
08:58 AM
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The difference is much greater than 100 ft. 100 miles would be a closer estimate. Is there a way to change it to a new projection without using the define project tool? Maybe these screen shots will help Spatial Reference & Extent for DEM: GCS for the GCPs
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04-17-2015
05:59 AM
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//1. What are we talking about in terms of the character and amount of misalignment between the images and the DEM?// The images and the DEM don't seem to appear anywhere near each other. When I try and view the entire extent it takes me from 1:627 to 1:18,559,691. //2. Does the point cloud also exhibit the alignment issue? You could throw the LAS file into an LAS Dataset and compare it to the imagery to determine this.// I put the las file into a las dataset and there were still major alignment issues. As you can see in the picture the GCPs are in the top left corner of the lidar data. This is a closer match than the actually DEM though. //3. I have never tried this but do you have any other correctly aligned elevation surfaces you could compare the DEM to? Or even a digital USGS topo? Perhaps if a reference surface has high enough resolution, you could use some distinctive terrain features found in both surfaces for georeferencing purposes.// The DEM that I've created is only about 250x130 meters and there aren't really any distinguishing features from it since it's a desert in Utah.
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04-17-2015
05:47 AM
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Hello, I'm working on a project where I've taken point cloud data obtained from a terrestrial laser scanner and converted it to a DEM using Lastools. I've also got aerial imagery taken from a helikite that has been georeferenced with ground control points. I now need to overlay those images onto the DEM so I can create a semi-realistic terrain model. My problem is that the DEM and the georeferenced images don't line up even though they all have the same coordinate system. I know I could georeference the DEM to the ground control points to fix it, but the DEM doesn't have any features that I could actually match to the control points. Does anyone have any advice that would help me get around this issue? Thanks, John
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04-15-2015
08:09 AM
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