Attributes in shapefile exports

[Eric C. Landgraf]

Walls includes several attributes in its shapefile exports. For example, the line export includes from and to station names, the X, Y, and Z of the segment, the computed length/azimuth/clino of the segment, and other metadata (date, etc. Bascially anything in the equivalent of a .3d file).

It would be helpful if Survex included equivalent attributes, or even richer data in shapefile or other georeferenced outputs. ("other" suggested because: ​http://switchfromshapefile.org/)

[Eric C. Landgraf]

shapefile attributes from walls

[Olly Betts]

What's "LINETYPE"?

[Eric C. Landgraf]

I took a look, and all the values are a Hex code. I assume it's walls' internal represenation of their colouring, line width, and dash pattern. i.e. probably not very useful or well-used.

[Olly Betts]

OK, and I assume CTR must be "CenTRe". The data we currently have for each leg is:

• the 3D vector after loop closure
• from and to stations
• survey the leg is in
• surveyed date of that survey (which can be a range)
• style (normal/diving/nosurvey/etc)
• surface flag
• duplicate flag
• splay flag
• various closure error info

Each station has a name, 3D position, and some flags: surface underground entrance exported fixed anon wall

[Eric C. Landgraf]

yes, that is correct. so CTR_Z is the elevation of the center of the leg.

Flags and styles would be useful to filter by. e.g. I might want a separate display style for surface lines, and want to filter out all splay legs.

[Joe Walko]

This functionality is crucial to those of use who incorporate the post-processed cave data into GIS software. Metadata included by Walls and Compass in the shapefile exports is used for symbology (color by date, for example), labeling, categorizing, and creating subsets, in GIS, of cave data based on certain attributes.

In addition to GIS, the shapefile attribute metadata is used for downstream analysis, and as input to apps one can use for generating and viewing 3D imagery - imagery where it's important to retain key metadata.

This metadata is also import for validation and analysis of post-processed data. One can easily see the final azimuth of any shot in Compass or Walls shapefile exports. That's far more difficult with Survex 3d output which is xyz coordinate based. Makes it hard to compare final shot azimuths without extra post-processing of the 3d data.

[Joe Walko]

LINETYPE is described in the Walls manual, 'Exporting Shapefiles' chapter, as "RRGGBBxx (RGB color/style)". RBG is the color selected in the Walls 'Segment" UI tab. The 'xx' style value maps back to the 'line style' one selects in the "Line style" one selects, where there are seven options - those 'line styles' are represented as 0 through 6 in the shapefile LINETYPE field. tab.

LINETYPE field in shapefile export is likely not used by anyone. Except for me :-). I assign a specific line-type style to all shots which are to be excluded from length, via Walls UI, then in post-processing, I leverage that to calculate accurate statistics. Needed only because Walls does not otherwise provide a rational way to exclude designated shots from total length.

In general, one would not ever depend on LINETYPE field in shapefile - that field is an anomaly in that it is based on user-actions via the Walls UI, and is not set in underlying WPJ or SRV data. It's semi-transient, and gets reset if one purges workfiles, in Walls.

[Joe Walko]

Both Compass and Walls include rich attribute metadata in their shapefile exports. This approach is similar, but available fields do vary. Both should be looked at here, not just the field Walls populates in its shapefile exports. Compass has fields which Walls lacks, and vice-versa.

McKenzie documents the Walls shapefile fields in the Walls manual - but I'm not seeing Compass documentation covering their shapefile fields. I can pull together something describing Compass shapefile fields if it'd be useful.