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Messages - Alvaro L

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1
General / Re: Elevation values of DEM
« on: January 03, 2020, 10:29:56 PM »
You will need check points to align against in non PPK/RTK solutions. Any way the best course of action to minimise errors is "mixed heights overlapping flight lines in opossite directions with off nadir images", so the different studies say. In my case when precission is not needed I align agaist public survey data, but if your work is going to be used by GPS tractors be careful about the precission needed.

2
General / Re: workflow for urban areas
« on: May 20, 2019, 10:40:42 AM »
However, building rooftops are the ones driving your GSD, so you will be doing a bit of oversampling on street level. If there is a buidling breaking the sorrounding heights you will need a special flight lines just for it.

3
General / Re: workflow for urban areas
« on: May 19, 2019, 06:10:39 PM »
In this case I would adapt fligh lines to urban grid so building do not shadow your street sampling. Take a good GIS cartobase and make your drone follow street center lines and then fill in with intermediate flight lines when overlapping is insuficient in between streets.

4
General / Re: workflow for urban areas
« on: May 17, 2019, 10:05:20 PM »
Urban areas are the most difficult case for a photogrammetry work. Usually a combination of oblique, zenital and detail pics should work but a good mission planning workflow is very important so you can optimise flights, pics and processing for a good result. I can't go into details but in short your usual planning software and clueless rectangular grid patterns won't work. Your flight pattern and camera angles should adap to urban grid, street width and building heights. I am also against doing it in a on single field data, you need to iterate in your planning approach, model photographing and software reconstruction loop. You need command of several software packages to do it right.

https://sketchfab.com/3d-models/montblanc-4998e976b9894acdaa93ade53075664f

Some universities have published papers about city sampling and reconstruction works, but they use some serious overload of tools and resources we don't have, like combination of laser scanning on car with airplane based areal photogrammetry with rigs that get to shoot several cameras at once plus GCP with total stations, university support and staffing, etc. Even so, I think it can be done exclusively on photogrammetry work if you get to understand what it is going on, for instance how to get pics from ground level and from drone level correctly aligned.

5
Title says it all, apply finished iterations if a mesh refinement is cancelled halfway, at least as an option, if that is ever possible for the algorithm. Thanks !

6
General / Re: Agisoft Metashape 1.5.0 pre-release
« on: January 17, 2019, 03:11:43 PM »
Hi

One thing I have noticed with new the meshing method based on depth maps is longer times to build textures, which is expected working with more detailed meshes, but I would be great if this department could get some boost in future versions.

7
General / Re: Agisoft Metashape 1.5.0 pre-release
« on: January 08, 2019, 01:31:55 PM »
Quite happy with the new meshing based on depth maps, I get much more quality for a given calculation time and more importantly, for a given set of tie points and therefore still photographs, since re taking field work takes a lot of time, energy and money. I still think that there should be a thresold for generating very small detail based on displacement mapping on  subdivision surfaces, since Agisoft generates good meshes anyway. This way I could squeeze more render quality and diffuse consistency in pos rendering operations in 3D packages.

Also I would welcome more advanced operations and workflows with regions (Multiple regions, boolean logics, non destructive workflows, etc). Anyway Agisoft rocks, I just sampled a 17 hectares old city with Agisoft and it is delivering, compared to existing GIS data, xtremely good relative accuracy even without CGP points !!! Of course there is a good workflow involved but heck I am impressed.

8
Feature Requests / Re: Less stepped quality settings
« on: January 06, 2019, 01:49:09 PM »
Thanks for your answer. One question I have is if I need to generate a dense cloud in order to generate a mesh from depth maps.

9
General / Re: Agisoft Photoscan: Medium vs Ultra High
« on: January 06, 2019, 01:46:32 PM »
chunk your project in different parts or divide it inside evey chunk using different regions in duplicated dense clouds. Divide and conquer.

10
Feature Requests / Less stepped quality settings
« on: January 04, 2019, 01:18:58 PM »
Hi

I think It would be great an intermediate step in dense cloud calculation, between High and Ultra high, that would mean multiplying calculating times X2 instead of current X4 respect to "High" dense cloud calculation times. Kind regards

11
General / Re: 3D point cloud optimization
« on: December 11, 2018, 02:32:05 PM »
Oblique images are used for urban enviroments where you need to sample also lot of vertical façades. Besides, oblique images can increase your task budget quite a lot. For forest sampling I think nadir images will do, you just need to use a good sampling strategy with good overlapping but also one that really adapts to terrain (and forrest ?) heights instead of sampling from a single plane height, which is something you will be able to do only with drones and good software. Sampling from a single plane height a varying terrain or forrest mass is calling for all sort of insufficient overlapping problems. Also you can adapt routes to sample forrest boundaries, if you are not flying a plane but a drone you can think and fly out of the grid. Remember that part of your nadir focal is actually sampling in an oblique way. 


12
Feature Requests / Displacement mapping
« on: December 10, 2018, 03:29:37 PM »
Hi

Displacement mapping for the finest detail, in some of its variants (traditional method, PTEX) applied to a subdivided mesh, instead of brute force mesh tesellation, would ease things a lot for many of us, with lighter meshes to work with, more flexible workflows (displacement mapping to a decimated mesh) and probably less memory footprint in each step. It would open photoscan works to other fields, like CG for video games production

13
General / Re: Import OBJ in Blender
« on: October 24, 2018, 10:15:39 PM »
Adding to what it is said by Alexey, Blender is not a GIS application and does not handle well units from points coordinates in the order of thousands, because it will work against mesh precission. Use a "temporal" coordinates system that keeps your mesh or point cloud as close as possible to the Blender coordinates origin.

14
General / Re: DJI Phantom 4 RTK
« on: October 17, 2018, 11:06:10 AM »
We have been told for years that DJI could not release a DJI GS app for our P4P plus in built screens because of android and voilà, they release a mapping app in their P4 RTK solution with an android  in-built screen.

Integrated solutions = full vendor lock-in, planned obsolescence, uncertain amortisation time.

If you don't believe me, ask matrice 210 rtk buyers how they feel 'bout this.

15
Pure CAD software is not good nor optimised for handling or rendering big amounts of mesh data since they are mostly 3D solids oriented applications, but they are quite good at handling orthophotos and point clouds

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