add feature_type method for polyline objects (sfc_LINESTRING)

[hcorson-dosch-usgs]

• Add a new feature_type method here for sfc_LINESTRING

[jordansread]

Really weird that there isn't a name in here for vector lines: https://www.fgdc.gov/metadata/csdgm/03.html

@hcorson-dosch do you have an example file or rds you could share that is the type of sfc_LINSTRING we'd like to support? I want to make sure we get something adequate for the tests and to make sure the feature counts are correct (e.g., making sure we're counting line segments instead of nodes).

[hcorson-dosch-usgs]

I ran into this error when I was trying to run extract_feature() on network.rds from delaware-model-prep (link) so that would be good file for testing it.

As for the FGDC Spatial Data Transfer Standard Point and Vector Object Types I'm pretty sure that string is the term used for a standard polyline (a.k.a. linestring)

[jordansread]

Based on the current fix I am working on in my fork:

readRDS('~/Downloads/network.rds')$edges %>% st_transform('WGS84') %>% extract_feature()

wbbox: -76.3879906
ebbox: -74.3807851
nbbox: 42.4544545
sbbox: 38.7894548
feature-ref: Vector
feature-type: String
feature-count: 459
states:
- state-name: Delaware
  state-abbr: DE
- state-name: Maryland
  state-abbr: MD
- state-name: New Jersey
  state-abbr: NJ
- state-name: New York
  state-abbr: NY
- state-name: Pennsylvania
  state-abbr: PA