Trimble Business Center

Hey Everyone,

I'm curious to know if anyone has experience with this or something similar?

We recently completed a survey at a very remote mine.  At the request of our client, we did not associate any "known" coordinates to our project.  So, no projections or other GPS related data.  We merely assumed 5000.00, 5000.00, set a backsite ASSUMING North, then completed our work based on exiting features (fences etc.).  This was supposed to be a one-time site visit, BUT it wasn't.  They've now asked us to come and do some additional work.  Some of that additional work included an aerial flight of the site.  

Now, my question is, how can i process my flight to our GCPs (that are assumed and not rotated correctly)?  I get a message upon completing the Absolute Adjustment that states the image is not valid.  

Before anyone says, "you should always use real-world coordinates", or "why did you do it this way?"  I just did!  Thinking that it was a one-time thing.  I know it wasn't good practice!  I'm very frustrated at the fact that I went against my better judgement.  Live and learn, right?

Hi Marc,

TBC includes UASMAster, which could be an option to solve your issue.

In earlier days of photogrammetry this was done using flight plan data. If you planned your flight before, you can just use these entries as approximate values.

If you do not have it - you can just digitize it. Use your GCPs into TBC, digitze approx. your drone positions as points into TBC, to get some X-Y coordinates and export it as a CSV. Modify the CSV to have some logical height value and IDs for the images you have and then you can run it in UASMaster - which is part of TBC.

Your CSV for your drone approx. GNSS positions should have entries in the order of ID-X-Y-Z:

0001, 12345.34, 23456.45, 250
0002, 12367.56, 23489.78, 250
...

Just Send your TBC Project with Send2UASMaster with your GCPs directly to UASMaster with your local coordinate system you have and stored.
Save it in UASMaster as Mapping project.

In UASMaster you can now import your CSV as external orientation (GNSS/approx) values.

Assigning them through the ID to the correct images.

Run a relative adjustment but do not use the GNSS for the adjustment. Depending how good your coverage is, your images should connect. You can also use in the Advanced settings the option to run an extensive tie-point extraction, enhancing the processing time but als enhancing the probablitiy to connect the images.

If the images connect, you are almost there and made the difficult part :-)

You can now start measuring the GCPs. They will probably be difficult to measure, as the pre-positioning will be not so good. Having signalized points or easy to find GCPs is here very helpful. Measure them all, hope you have more then 3 GCPs....

Run the absolute adjustment. Again do not use GNSS and if you do not have too many GCPs, leave in the first try the camera calibration off. Give the GCPs a logical standard deviation.

Does it sound complicated? Yes, it is! But it can be done, but there are many pitfalls on this way. If you have enough GCPs you can still achieve a good quality (And of course then activating the camera calibration in the absolute adjustment is recommended!).

Cheers,
Tom