[Talk-us] Updating unchanged TIGER imports to TIGER 2013
enf at pobox.com
Sat Mar 16 18:35:42 UTC 2013
Thanks for the background. I'll skip over the TIGER hydrography, then, but
it's surprising that so much more of the NHD data is in OSM in some states
than in others.
On Sat, Mar 16, 2013 at 10:37 AM, Michael Patrick <geodesy99 at gmail.com>wrote:
> > The other thing that has come up is that there are a lot of TIGER edges that
> do not correspond to OSM ways in either their old or new version In
> Indiana most of these seem to be linear water. Were these intentionally
> excluded from OSM? Or would it be useful to try to pick them up as part
> of the set of changes representing additions to TIGER between 2006 and
> 5.10 Hydrography
> Hydrography features and attributes are available by county in the
> following shapefiles:
> Area Hydrography County-based Shapefile
> Linear Hydrography County-based Shapefile
> The Area Hydrography Shapefile contains the geometry and attributes of
> both perennial and intermittent area hydrography features, including ponds,
> lakes, oceans, swamps, glaciers, and the area covered by large streams
> represented as double-line drainage. Single-line drainage water features
> can be found in the All Lines Shapefile and Linear Hydrography Shapefile.
> The Linear Hydrography shapefile contains all linear hydrography features
> with “H” (Hydrography) type MTFCC in the MAF/TIGER database by county. The
> shapefiles are provided at a county geographic extent and in linear
> elemental feature geometry. The content of the linear hydrography shapefile
> includes streams/rivers, braided streams, canals, ditches, artificial paths
> and aqueducts. A linear hydrography feature may include edges with both
> perennial and intermittent persistence.
> The artificial path features may correspond to those in the USGS National
> Hydrographic Dataset (NHD). However, in many cases the features do not
> match NHD equivalent feature and will not carry the NHD metadata codes.
> Single-line drainage water features include artificial path features that
> run through double-line drainage features such as rivers and streams, and
> serve as a linear representation of these features. Shorelines for area
> hydrography can be found in the All Lines shapefiles with MTFCC set to
> either “P0002” (shoreline of perennial water feature) or “P0003” (shoreline
> of intermittent water feature).
> > I believe TIGER water features were excluded because NHD data is more accurate
> and comprehensive in most locations.
> Somewhere else in the processing steps documentation, they mention that
> they simplify and adjust either, or both, to eliminate braiding, etc., (
> like where a winding road follows a oxbowed river) - and that adjustment is
> tempered if either or both according to the significance as statistical
> area boundary between census periods.
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