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Author Topic: Difficulties measuring using scale bars  (Read 3469 times)

William Ringle

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Difficulties measuring using scale bars
« on: March 06, 2016, 10:53:08 PM »
I am having difficulty using a scale bar to measure between two points, and the manual is not very clear on the procedure. I am able to set marker points (both on photos and directly on the model) and then can create an initial scale bar using two of the points. I then can also click on View Source and enter the distance between a pair of the points. Any time I toggle back to View Source, the value is still there, the line between them is highlighted, as are the points. So, up to this point all is OK.

My difficult comes in the next step. I go to the Reference tab, click View Estimated. I select another pair of marker points, right-click on them, and select Create Scale Bar. The bar is created and is selected. However, no Distance est value appears next to it. I double click on the area - nothing. The boxes next to both scale bars is unchecked. Can't figure what I am doing incorrectly, and in fact it worked once when I was clicking randomly about. Unfortunately I couldn't replicate it.

I also notice that if I right-click on the marker point and select Filter Photos by Marker, nothing appears (though the markers do in fact appear in multiple photos).

Using v. 1.2.3 Pro, Windows.

Any help would be greatly appreciated,  I really need the information.

Thanks!

Alexey Pasumansky

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Re: Difficulties measuring using scale bars
« Reply #1 on: March 07, 2016, 12:13:06 AM »
Hello William,

Instances in the Reference pane that are used for scaling purposes should be checked on. And those that are assumed to be used for measurements should be unchecked.

In case all the scale bars are unchecked (and there is no other scaling data in the Reference pane) PhotoScan has no information about any dimensions, so estimated tab is empty.

Also you cannot use marker with zero projections, as it has no position defined in model space.
Best regards,
Alexey Pasumansky,
Agisoft LLC

William Ringle

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Re: Difficulties measuring using scale bars
« Reply #2 on: March 07, 2016, 01:43:47 AM »
Thank-you Alexy for your response, but I am still having trouble, although I made sure I had checked the scaling scale bar (points 1-2). Attached are screenshots. As mentioned, Filter by Photos has nothing for any of the marker, but if I click Show Info for each of the markers, the related photos do appear (4 for the first marker, 10+ for the others).

Regarding your observation concerning coordinate systems, the manual (p. 48) states: "Model coordinate systems must be also initialized before the distance measurements can be performed. Alternatively, the model can be scaled on known distance (scale bar) information to become suitable for measurements." This seems to indicate that a projection is NOT necessary for measurement when a (known) scale bar distance is employed. Is the manual incorrect?

N.B. Answered my own question. Coordinate system need not be defined, but object can be scaled with a single scale bar. My mistake was not hitting the Settings button after defining the scalebars. Maybe the manual should be updated to reflect that necessity and the "settings" button have a more appropriate name.

Is there a way to reset scaling, say if one wishes to use a different scalebar as the primary scale factor?
« Last Edit: March 09, 2016, 12:07:51 AM by William Ringle »

MeHoo

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Re: Difficulties measuring using scale bars
« Reply #3 on: May 05, 2016, 04:55:27 AM »
Just curious, as I plan to start using scale bars soon.. was this ever resolved?

Alexey Pasumansky

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Re: Difficulties measuring using scale bars
« Reply #4 on: May 05, 2016, 12:15:20 PM »
Actually, after inputting the known distances for the reference scale bars and checking them on in the Reference pane it is necessary to press Update button on the pane's toolbar to apply the scale. When you open the Reference pane Settings dialog and exit it by hitting the OK button the update operation is also performed.
Best regards,
Alexey Pasumansky,
Agisoft LLC