Topics

1

General / DEM Transformation AUSTRIA for RTK Modells

« on: March 18, 2023, 09:42:51 AM »

Good Morning,

I am using Agisoft since 7 years now. First with an German Multikopter, the a Phantom 4 Pro and now a Mavic 3 Enterprise and RTK modul.

Main purpose is surveying of quarries.

Since the beginning I have a Trimble R6 Rover, using the austrian apos correktion data. Works pretty well.
The austrian Grid (EPSG: MGI 31255 or 31256) need a local correction on the trimble rover. That means, Fixpoint are measured and there has to be a local correction on the survey controller.

This can not be applied on the Mavic RTK system. Therefor there is a deviation between the GCPs (measured by Trimble) and the RTK Model.

Difference can bei:
X = -0,02 m
Y = 0,64 m
Z = 2,34 m (actual values from this week).

Now the question:
- If I use the GCPs on the RTK Modell, the overall deviation is about 0,10 m, but the modell difference on height ist stll to much.

- Is there a funktion to get the DEM and Ortho modified by these values?

regards
Martin

2

General / Using RTK and Ground control Points

« on: March 04, 2023, 05:56:06 PM »

Hello Together,

I am using Metashape since 2015 for surveying of quarries. I love the programm, the results are very good.
Usually I use a Phantom 4 Pro and a lot of ground control points (up to 3-4 / 10.000 m²). GCPs are measured with Trimble R6.

Now i have bought a Mavic 3 Enterprise, using also the RTK Modul (using Network). I works well, BUT:

Total accuracy is lower than using just the P4P. This is, because Trimble R6 is using a local ajustment to the austrian reference system (which is not available to the MAVIC).

Total error is about 0,08 cm, which is not so much but gives huge deviations in VolumeCalculation.

Now the question: How can I decide, using the "location of the fotos or not?"

Thx,

Martin

3

General / Significant improval between Metashape 1.7. and Agisoft Photoscan Prof. 1.2.6.

« on: February 18, 2022, 10:11:20 AM »

Hello,

I am using Agisoft Professional 1.2.6 2843 (64 bit) since 2016. I am satisfied with the results.
I am currently using a DJI Phantom 4 Pro (fixed shutter, 20 MP, Camera uncalibrated) for surveying purpose.
Usually flying at an altitude of 100 m (85% Front overlap, 67 % Side overlap)  I am getting an error of 0,185 (pix) and a Error of 0,027m of the GCPs.
I am using usually 15 - 30 GCPs on an area of 7 - 20 hectares, using a Trimble RTK GPS System (inkluding Glonass) for GCP Measurement.

Absolutely ok, no more accuracy needed. Ground solution is about 9,4 cm/pix; point density 113 pts/m².

Now I have tried a photogrammetry of Fotos made by DJI Mavic 2 Pro. Camera uncalibrated; The results are not well. It can depend on low number of GCPs (only 8 of them on 25 Hektares) and high number of fotos (475 #).

Best result was: 0,214 Image error; 0,077 m Total error. (using only 50 % of the pictures). Reprojection Error was 4,22 pix.

The best result of Metashape Professional 1.7.2. was total error xyz 3,71 mm (!), which is at least half of the error.
Camera Reprojection error was 7,02 Pix.

Questions:

- is the algorythm of Metashape that better than the old version of Agisoft?
- Is there any improval for analysing rolling shutter fotos?
- is ist worth spending money for an upgrade?

Regards

Martin

4

General / Using QGIS for Control of the DEM; Surveying of Quarries

« on: March 08, 2017, 12:16:29 PM »

Hi Folks,

I am always looking on the accuracy of the DEM and possibilities to test it. I am using GCPs, measure them with GPS (accurate Trimble one).

Now the idea is: I measure different points on the surface of the quarry (between the GCPs) and around the model. I do not use any markers on this points. I export the measured points into a shp-file (as points) and use the point sampling tool of qgis to make a projection on the surface of the DEM.
Export the points into CSV-File and compare the surface levels with the GPS - measured heights. 

Advantage: information from outside AGISOFT and quicker than checkpoints.
Disadvantage: 10 min additional work on the PC. No information in x / y deviation.

Any Ideas and comments?

Regards

Martin

5

General / Volume calculation

« on: January 17, 2017, 10:20:02 AM »

Hi there,

I am using Agisoft Professional 1.2.6 build 2834: For volume calculation:

Surface area and volume measurement
To measure area and volume

Draw a polygon on the DEM using Draw Polygon instrument to indicate the area to be measured.
Right button click on the polygon and select Measure... command from the context menu.
In the Measure Shape dialog inspect the results: see area value on the Planar tab and volume values on the Volume tab.
PhotoScan allows to measure volume above best fit / mean level / custom level planes. Best fit and mean level planes are calculated based on the drawn polygon vertices. Volume measured against custom level plane allows to trace volume changes for the same area in the course of time.

[Note] Note
Measure option is available from the context menu of a selected polygon. To select a polygon, double-click on it. A selected polygon is coloured in red.
 
When doing this, the result is always a perimeter and not a volume. Is there a bug or am I wrong?

regards

Martin

6

General / Virtual Surveyor

« on: August 03, 2015, 05:14:08 PM »

Hi Folks,

currently I found the program Virtual Surveyr to create Breaklines from the Agisoft Elevation model. At the moment i am using the Qgis solution, to draw breaklines by hand on the orthofoto and save them as shape file.

With the shape files i am using a qgis routine to write the points on the level of the surface model (Point sampling) and export them to an Acad 3d-File, with the right description, level etc.

Which solution do other surveyors use? Is there anybody already using the virtual surveyor software?

Regards

Martin

7

General / MGI Austrian Map Date

« on: January 23, 2015, 08:08:25 PM »

Hi Folks,

I am a Newbie, using Agisoft Photoscan Professional the first time. I am a mining engineer and use the software for quarry surveys with an octokopter UAV.
I have currently problems to find the austrian Map date (Gauß Krüger M31 and M34 in the list of the coordinate systems.

Can anybody help me?
2nd Item is, that I am able to export an orthomosaic file, but the DEM does not work. Any suggestions?
Thank you for your help.

Regards

Martin
PS_ any answer in german is welcome (coming from Styria in the heart of austria)