Topics

1

General / No match between nadir and oblique aerial photography

« on: September 14, 2017, 07:57:34 PM »

Hello guys!

I´ve been using photoscan for a short while and must confess although I´m getting the hang of it, I am no expert so my question might be a little essential.

I´m working on monitoring changes in semistable dunes. For my purposses I generate DEMs and orothophotography with Photoscan Pro using aerial photography taken with drones. Recently I encountered a problem when aligning a chunk. I always group nadir and oblique frames in the same chunk in order to align them toghether and get the most accuracy posible, but in this chunk I am getting no alignment with the oblique imagery. When analizing matches I noticed oblique frames have no valid tie points where there should be. My parameters are the highest accuracy enabling generic preseleccion and am using 40 000 and key point limit and 4 000 tie point limit. I am also masking some of my oblique imagery since I am getting some background wich I am not interested in.

I tried disabling reference information and realigning using only GCP but I am getting the same results.

I include two screenshots, one of nadir and one of an oblique frame of the same area where a GCP is visible.

I have generated numerous projects of this same area using the same flight plan in different dates, but I am only having trouble with this project. I would really appreciate if you could help figure out why.

2

General / Banana shape effect

« on: September 15, 2016, 11:01:08 PM »

Hello Agisoft community!

I have a quick and somewhat simple question.

I´ve been working with photogrammetry to quantify erosion on a certain beach. To do so I take aerial photography with a UAV  and then generate dense point clouds with Agisoft Photoscan Pro. Due to the fact that I need really precise measurements I have been using GCP´s which I georeference using an RTK GPS to geotag our models. All tough the GCP´s are permanent marks that we placed along the coastline, and have been used in the monthly models to standardise them, some models have resulted with a low banana shape effect.

What might be causing this? I have been flying monthly since march using the same flight plan and geotag my models with the same GCP´s.

I´ve attached two images, one corresponding to march and the other to august so you can se the difference between them even after been georeferenced using the GCP´s.



Thanks in advanced

3

General / Georeferencing using GCPs

« on: September 05, 2016, 10:31:50 PM »

Hello Agisoft community!

I have a quick and simple question. When importing my photographs and if they are georeferenced and at the same time I am using GCP´s, does photoscan georeference the model using both the photographs and the markers GPS information? Or by using markers does it automatically omit the photographs information?

Thanks in advanced!

4

General / Projection inconsistency

« on: April 27, 2016, 10:07:55 PM »

Hello Agisfost community!

I´ve been working with A. Photoscan pro for about a year now with the topic Coastline monitoring and I am more than pleased with it.

However, on the last 2 models I´ve worked with I have noticed a projection inconsistency on my models. Both chunks have been generated with the same drone (Inspire1 and its respective camera) under the same flight plan parameters (altitude, speed, waypoints, etc., with the camera always pointing nadir), and the models too have been generated under the same alignment and dense point cloud parameters. However one model shows a somewhat more round projection than the other wich has a more planar. Inspire1 has its own GPS wich is the data I've used to georeference my models but I am not using ground control points.

So my question is, what could be generating this inconsistency and how can I fix it?

I´ve attatched screenshots of both models to make my problem more clear.

Thank you very much in advance!

Daleth C.

5

General / Merging chunks

« on: January 26, 2016, 08:56:13 PM »

I have been working with reconstructing coastline DEM.

I recently took aerial oblique and vertical photography, if I'm interested in generating one model with both chunks, would you recommend generating two clouds and then merging them together?

I tried so and when merging them together they didn't align properly. They both have the same georeference system and were georeferenced with the same GPS.