Dref's Srf's and file size

[jmayo-EE]

I'm testing cropped and data clipped surfaces through drefs. I am trying to push the new firm into breaking the base data up in an attempt to reduce file size and performance. The sheet files I am creating with the same base data is larger with cropped and data clipped surfaces than it is with the full surface. Anyone else seing this? See the attached image.

File names describe the differences in the files. They are all built with the same 8 xref's and surfaces. I used two different templates. The larger files from a revised NCS template. The ones with 'New Template' in the name use the same slimmer template. The full surface is 3400 ac and the cropped and data clipped srf's are about 280 Ac. I would expect the files with the full surface to be significantly larger but this is not the case. Anyone have any insight or similar tests to compare too?

Also note that the original aerial linework file is a 256 MB dwg file. This is xref'ed directly into Test 1. All the other files have this same data broken up into the 8 base xref files.

[AlmasSuljevic]

Hi John,

Just to report my findings to you. I have created very large surface from LandXML in NCS template and taht file was 40 MB. I then created cropped surface from a polygon in new file (same template) and that drawing was  9 MB (as expected). 

Do you have any knowledge if the drawing had objects from DGN in there? How are other surfaces behaving?

[jmayo-EE]

Hello Almas,

The base data for the surface (acad blocks and pline contours) was from an aerial survey. I would bet that they were dgn before dwg.

John

[jmayo-EE]

I need a bit of time for confirmation. I was told that many of the company's hired in this area for aerial are or were using LDD.

[jmayo-EE]

Dwg aerial data converted from 3d steroplotter data.

[rl_jackson]

It sounds as though your data was generated in C3D, depending on how it would have been created (i.e. dtm file or tin lines, polylines) that could be the causing some of the problem with file size. I have had to create surfaces using from aerial data, and have found that most users dont strart with the right info. Aerial files generally come with the planemeterics and contours, and then a drawing with breaklines and points. The breaklines and points is the one that should be used. Converting the points to C3D Points and exported to a file, then adding the file to the surface. then adding the breaklines. This generally reduces the file size substantially. You may want to investigate how that surface was originally created. Using the Planemetrics drawing usually ends bad, and will quickly quadriple file size

[jmayo-EE]

Hey RL,

Yeah I know this is not the best way to build a surface but this is the best data available. We have AutoCAD blocks at elevation and contours. If we want new data we fly it again and that's just not going to happen. 🙂

Almas, Also note that the contours were wblocked to a new file to build the surface with. Map data was not created in the file.