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Hi, I can't figure out how I get Cross Sections (3D-lines) out ouf a point cloud.
I can use the path-profile tool and can export the points of one profile, but I don't get a 3D-line.
Is there an other tool or function that I don't see?
(I would not like to transform the pointcloud to an elevation model first)
Hahaha - I got it if anybody wants it...
I moved the sketchup model in sketchup to the right elevation, then exported it to KMZ, then imported it, ran a rotation, ran a translation and it is in the right spot. I wish I had completed more oblique images in my drone flight as the DSM looks a little meh.
dpitman said:Hi Folks,
I don't yet have GM.
In GM, how do you examine the coordinates of check shots to compare them to surveyed values?
Since you're using the term "GCPs", I'm assuming that you're a drone user. The way I compare checkshots to my drone-derived DSM/DTM is:
1: Import GCPs
2. Use calculate/copy attributes tool to copy "ELEVATION" attribute to a new attribute called "Observed"
3. Turn on DSM/DTM layer if it's not already on
4. Select all checkpoints and right-click--->analysis---> apply elevations to features
5. Use calculate/copy attributes tool to copy "ELEVATION" attribute to a new attribute called "Predicted"
6. Use calculate/copy attributes tool with the formula OBSERVED - PREDICTED, and write it to an attribute called "Delta"
7. change display labels to "Delta" attribute. Export as CSV to calc RMSE, if needed.
You can also convert the DSM/DTM to a point cloud (or "Create points at elevation grid cell centers") and use the lidar QA/QC tool. The lidar tool will sample nearby points. The workflow above will sample a single cell/pixel at the same XY coordinates as your control point.
I use the autoclassify-broud-option in GM quite often the following way:
1) split up big pointclouds in tiles of about 5 million points (100m x 100m in my case) with the exportfunction of gm (create tiles when exporting)
2) take one representative tile and test different parameters with the autoclassify ground-points option. (my favorite binsizes are 50cm and 100cm, for the min height dev I test 5cm, 10cm, 15cm,...,50cm - often 25cm is the best in my case)
3) export the autoclassified-test-tile and import it again but only the ground points and IMPORTANT: with the option "treat heights as deaths"
4) autoclassify the imported test-tile a SECOND time with the binsize like before and min height dev 5cm.
So the surface gets autoclassified "from both sides", which give often better results and a smoother surface-pointcloud.
5) If the results are ok I do the same with the other tiles and merge the all together by exporting into one big "ground pointcloud".
Hope it helps and sorry for my poor english...
Global Mapper v19.1.0 (b021218) (355) [64-bit] [+LIDAR] - REGISTERED
I am using GM to contour drone collected point clouds which involves a lot (a lot!) of iterations of point cloud cleaning, gridding, and contouring and have a few feature suggestions/requests:
1. Retain all of the options selected in the Create Elevation Grid and Create Contours dialog boxes to be persistent, so the next time you open them the options last used are there. Especially the "Grid Bounds" and "Contour Bounds". Currently in Gridding, the grid spacing always reverts to Auto. In Create Contours the Contour interval, x and y axis, the checkbox for "Discard Closed Lines Shorter than X meters" (while we're at it, it would be nice to have this value in the current display units rather than always in meters)
2. Allow selection of the Cropping Area feature within the dialog box under Contour Bounds and Grid Bounds. Almost every time I open one of the dialog boxes, i have to close it and go select my Cropping Area feature and then reopen it because forgot to select it again. Better yet, also retain that cropping setting from the last time the dialog box was opened.
3. Include the Grid and Contour generation settings that were used to generate them in the metadata of the resultant feature layer, including the time and date. Perhaps even include the feature layers that were used as input data to create them too.
An option to include them in the name of the feature would be handy too. For example, I typically name them something like "Grid 5/2 1:44 2x2 ND 16.1" for a grid created May 2 at 1:44pm with 2x2 spacing and No Data set to 16.1, and "Cont 5/2 1:50 2x2 Disc 2.5 s=.010" The time is there so I know which grid version I made it from.