georef project using Google Maps

[GrinGEO]

Im new to Photoscan and triying out some features for aerial mapping.

I have done a aerial survey of a region withouth having Ground Control Points.

Im wondering if I can georef a photoscan project using some kind of google maps overlay?

Any way to do this?
Thanks for helping

[Alexey Pasumansky]

Hello GrinGEO,

In principle, you can do that, for example, using the following brief instruction as a reference:
http://www.agisoft.com/pdf/PS_1.1%20-%20Tutorial%20-%20PS_to_GE.pdf

However, please note that by default PhotoScan treates the altitude values for geographic/projected coordinate systems as above ellipsoid (unless compound coordinate system is used that is based on different geoid model), while in Google Earth they are above sea level, so you might need to adjust the altitude in Google Earth for the exported model.

[GrinGEO]

Im wondering if there is any way to do a georef with google maps coordinates or Ground control points after the dense points have been generated.

Im not sure how Pix4D does, but it looks like the georef is done not in the single pics like photoscan - wich in my opinion is really much work - but when the pics are already stitched togheter.

Is there any way this could be simplified in Photoscan. Cause it's really difficult to find the GCP on a project with about 500 pics that are not aligned...

I hope you understand what I mean.

Thanks for helping

[Alexey Pasumansky]

Hello GrinGEO,

You can create marker in the model view by clicking on the desired point with the right mouse button and using Create Marker option from the context menu.

[GrinGEO]

Thanks worked great...
now it looks like I have to purchase the pro license.... 

one more question: will the already calculated dense cloud then be stretched/moved/modified with the ground control markers?

[Alexey Pasumansky]

Hello GrinGEO,

You can put markers even after the processing of dense cloud and mesh is finished. Pressing Update button on the Reference pane after inputting marker coordinates will translate and scale the model accordingly.

[GrinGEO]

that's a great news. Thank you so much for your support

[GrinGEO]

Today I had a fly and unfortunately I could not georef the singel pics so I had Agisoft to do the entie processing.

I have now the problem:

1. the model is entirely upside down. How can I reverye the Z axis?

2. I can find the XY coordinates out from google maps and I can define the starting point from the drone as marker with the height 736m in Agisoft. Unfortunately I do not see that the model has now been georef and it didn't fixed the upside down issue. How can I manage this issue?

Thanks for helping

[Alexey Pasumansky]

Hello GrinGEO,

You need at least three control points that are not laying on the same line for georeferencing to avoid any rotational degrees of freedom. Having only single control point doesn't give any information about the direction of the coordinate system axis.

[GrinGEO]

Dear Alexey

I placed 3 markers with the XY coordinate from google (no altitude informations)
and one marker with the altitude information from drone GPS of starting point (but withouth XY)

still the model is upside down

[Alexey Pasumansky]

Hello GrinGEO,

In PhotoScan there's no option to input only one or two coordinates from three for the point. Do you mean by "without having coordinate information" that the corresponding coordinates a zeros? Maybe you should refine the accuracy settings for the markers like 1/100 for those that do not have valid altitude information and 1000/10 for the take off point, but also I suggest to input more or less adequate XY information for it, as 0,0 doesn't seem to be correct in any case.

[GrinGEO]

unfortunately I do not have altitude Z coordinates from Google Maps, there I can only find XY

on the other side from the starting point I have only the GPS altitude from the copter, but not XY accuracy

any solution?

[Alexey Pasumansky]

For example, you have
point 1: x1, y1
point 2: x2, y2
point 3: x3, y3
and point 0: z0

I suggest the following:
point 1: x1, y1, z0 -> set accuracy 1/100
point 2: x2, y2, z0 -> set accuracy 1/100
point 3: x3, y3, z0 -> set accuracy 1/100
point 0: x, y, z0 -> set accuracy 1000/1
where x and y are somewhere close to the first three points.

[GrinGEO]

where can I set the accuracy? there is no options under the markers list

[Alexey Pasumansky]

Hello GrinGEO,

Right-click on the selected markers, choose Set Accuracy from the context menu.