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Author Topic: Problem Exporting Contours  (Read 6315 times)

Lord Beowulf

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Problem Exporting Contours
« on: December 01, 2015, 03:58:35 PM »
Using the new contour feature in V1.2.0, when I export, the highest contours don't seem to make it into the export.  Regardless of what I import into, those lines are missing.  Doing some experimentation, if I export polylines I seem to get the bottom half of what I'm looking for.  If I export polygons, I seem to get the upper surface that's missing from the lines output.

In addition to fixing the export, it would be much more helpful to have the option to export to DXF or some other non-GIS format, since that's the reason I need the contours to begin with is to move into another CAD package.  If users have to buy and use a separate tool to convert the PhotoScan output and have an extra step in the process, the contour option isn't really very helpful over the previous version where you had to use an external tool to generate and export contours. 

Thanks!

Beo

Alexey Pasumansky

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Re: Problem Exporting Contours
« Reply #1 on: December 01, 2015, 04:05:08 PM »
Hello Beo,

Shape files may contain only single type data: either polylines or polygons, so the contour lines generated by PhotoScan are actually represented by the both sets.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Lord Beowulf

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Re: Problem Exporting Contours
« Reply #2 on: December 01, 2015, 08:31:41 PM »
Hi Alexey:

I'm not sure you understood my report.  If you examine the images in the pictures attached to the previous post, the first shows the screen in PhotoScan, while the second shows what I get when I import the poly-line contours into ArcGIS or any other package.  On the other hand, if I export as polygons, I get the image attached to this post, which appears to be the missing half of the data from the poly-line output, but as polygons.  Is there something I'm missing that's causing the missing data?


I'll also reiterate the request for a non-GIS export format (e.g. DXF) to eliminate the intermediate steps.

Thanks,

Beo

Alexey Pasumansky

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Re: Problem Exporting Contours
« Reply #3 on: December 01, 2015, 08:48:59 PM »
Hello Beo,

Single shape file cannot store different data type at the same time. So there could be either polylines or polygons. It means that the contours shown in PhotoScan window can be represented by two Shape files.

As for the DXF format, we already have this feature in our list due to big number of similar requests, so it would likely appear in one of the 1.2 updates.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Lord Beowulf

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Re: Problem Exporting Contours
« Reply #4 on: December 02, 2015, 01:32:37 AM »
Hi Alexey,

Sorry, I can see I'm not getting my point across clearly.  I'm NOT trying to combine the polygon and poly-line outputs.  I'm simply trying to get all of the contours to export in one format (poly-lines preferred).  If you look at the attached picture, I've highlighted the problem in each case in blue.  The top image is the source data with contour lines throughout the entire area.  If I export that as poly-lines, all of the contour lines corresponding to high areas (the blue region) are missing.  If I export as polygons, all of the contours for low regions are missing (blue region).  In either case, I only get about half the contours when I import, and they're the opposite half depending on which format I choose.  It also doesn't matter what tool I use to import.  So unless there's some setting I'm missing in Photoscan that's controlling this, this doesn't seem to be the correct behavior.

Thanks,

Beo 

Lord Beowulf

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Re: Problem Exporting Contours
« Reply #5 on: December 02, 2015, 01:40:47 AM »
Or are you telling me that PhotoScan is differentiating between open and closed contours?  Thus, the poly-line formatted file only has open contours and the polygon format has only closed contours?  That seems to be an odd limitation, and requires another package to load two files and re-create the original contour map.  If it truly is a limitation of the shape file format (odd limitation) it would seem that you could close the contours around the perimeter in order to make them all apply to the polygon format.   

BTW, thanks for the update on the DXF format.  Hopefully that won't have the same limitation and you can export all the contours to one file.

Thanks,

Beo

Lord Beowulf

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Re: Problem Exporting Contours
« Reply #6 on: December 02, 2015, 03:51:37 AM »
Hi Alexey,

Ok, so I did some investigation of the Shape file format and understand the restriction of only having a single type of shape per file.  I don't really see that as a problem and is what I would have expected by the options for export.  Where the disconnect is in what I now realize is between closed contours and open contours.  Given the way ArcGIS handles these files, it's apparent that their definitions for polygons match the standard graphical definition.  A closed polygon is a shaded/filled object while an open polygon (poly-line) cannot be filled.  Thus, when I open the polygon export in ArcGIS, the default is to show it as a solid colored surface with no borders representing the contours.  I can change that setting, but it shows that's not what ArcGIS is really expecting out of a polygon shape file.  I'm assuming that's intended for surfaces only, and would support creating a color gradient map, etc. 

Given the restrictions of the two formats, what I would have expected was that the poly-line would have output all of the contours in the project as poly-lines, so that even the closed contours are essentially open polygons.  Likewise, the polygon output could output all of the contours by applying the same border that's defining the perimeter of the contour map to each open contour so that they're all polygons.

At any rate, I now believe I understand what you were trying to explain in your responses, but not why that needs to be a limitation to exporting all of the contours in either one format or the other.

Thanks,

Beo