Exporting e57

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AleksKS
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Exporting e57

Post by AleksKS »

I am attempting to export a file to e57 format but for whatever reason the box that allows me to change my units is locked/grey-out and won't let me change it. It keeps defaulting to meters so I am currently unable to export in US survey feet. Would anybody happen to know what is causing this?


Thanks
TMillington
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Re: Exporting e57

Post by TMillington »

As I understand it, .e57 is a file format that is only designed or specified to use metres, so this would be an issue with file format rather than with RealWorks.

Several other of the available cloud export formats in RealWorks will allow you to specify US feet as the export unit, if that is what you need.

Really it all depends on what you are intending to do with the exported data and/or which software(s) you're planning to take it into.

Regards
AleksKS
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Re: Exporting e57

Post by AleksKS »

I exported in e57 using meters and brought the same back file back into a project with US Survey Feet as the project units and the structure measured in feet. If this happens I would have to think it converts it before it creates the file? Either way, the US feet held. Maybe because I exported it while the project was set to US feet.

Appreciate your help.
Earthworm3d
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Re: Exporting e57

Post by Earthworm3d »

I would imagine like a lot of scanner software the data is stored internally as meters. When you change your project units it is doing the conversion to show you the proper unit without changing the internal data. This is the way cyclone works.
Probably the only time you would need to change the units if you are going to a different software on export or importing a non e57 cloud.
I use e57 as much as possible because it is a binary format and is in meters which makes for smaller faster files. It also carries information on scan position which will give you realview if you are using recap.
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Re: Exporting e57

Post by quirysse »

I confirm that the reason the units are greyed out in the E57 export dialog of Trimble RealWorks is because the E57 specifications says that all values must be stored using SI units. Thus length is in meter. It doesn't matter what unit your project was set to in TRW, all coordinates will be stored in meters when exporting to E57.

This is a bit different from LAS where one can specify the unit inside the file itself. Of course, it is then the responsibility of the reading software to read and interpret this information properly (this is not always the case).

In the case of E57, there is no ambiguity about the unit, thus software are supposed to know how to interpret E57 values and how to convert it to the user prefered unit.

If one software starts to write E57 using other unit than meters, that would open a big breach of incompatible E57 files that one would never know exactly how to interpret. This is what happened with PTX/PTS where meters should always be used (see Cyclone spec: http://w3.leica-geosystems.com/kb/?guid ... 79E5937CB2). Unfortunately, for some reasons many PTX/PTS files have been written using other units. So many that some software are now proposing the unit as a choice when dealing with those formats.
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