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Author Topic: exporte dense cloud in ASCII format  (Read 1837 times)

wyk

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exporte dense cloud in ASCII format
« on: December 04, 2016, 04:15:13 PM »
Hello :)
I need to export my dense cloud in ASCII format as best as possible

I dont understand what is the number of digits of accuracy option (automaticly fixed at 6)
i try to export with 1 and 10 : the number of point are the same...
But the dense cloud seams more dense with 10 value...

Who ca explain to me ?

I want to export with the best précision and density
BR

stihl

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Re: exporte dense cloud in ASCII format
« Reply #1 on: December 05, 2016, 02:16:13 AM »
Hi,

I believe it has to do with how many decimals each point coordinate in the dense cloud should have when you're exporting it to an ASCII format. I don't think changing this number will affect the number of points in the dense cloud.
You can simply test this by checking to see how many points each dense cloud has in a free program like cloudcompare or quick terrain reader.

James

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Re: exporte dense cloud in ASCII format
« Reply #2 on: December 06, 2016, 05:39:31 PM »
Yes it is the number of decimal places. If your data is in meters and the accuracy of data is in the millimeter range then you probably don't need more than 3 decimal places (0.001m = 1mm), but for geocoordinates which may be in degrees latitude and longitude you will need 6 decimal places just to be precise to the nearest 11cm (1degree latitude = 111,000m so 0.000001degree latitude = 111mm)

If you export your data with precision = 1 then the points will be rounded to 1 decimal place and points that may have had unique coordinates with 6 decimal places will now share the exact same point and appear as one point with clear space around them. There are still the same number of points but many of them will be 'duplicates'.

If you export your data with precision = 10 then it is much less likely that any 2 points will share the exact same coordinates and so you will see many more discrete points in your cloud.

There is no facility in photoscan to change the number of points in your point cloud other than to manually remove, use gradual filters (sparse cloud only), classify points and then delete classes or select by colour (dense cloud only) or just build the cloud at a lower setting in the first place.