Honoka'a & 'Ahualoa

Notes on using the VTP software to create a 3D model of the small town of Honoka‘a and neighboring area of Ahualoa.

Small Elevation Area - Honoka'a3

• extracted directly from 10m DEM, NAD83 at (238600.0, 2219400.0), ( 6000.0, 6000.0)
• at a 2k grid, this is 2.93m spacing (honoka'a3_2k.bt)
• the roads are imported from DLG, and adjusted to align with the NAD83 elevation (honoka`a3.rmf)
• roads are used to deform elevation with 2m margin and fade-off zones, resulting in (honoka'a3_flat_2k.bt)
• attempted to georeference an aerial (#1, below) resulting in:
  • coverage of area (241245.0, 2220960.4), ( 1601.6, 1474.9)
  • at 1639 x 1514 pixels, that's spacing of 0.97718, 0.97417; made corresponding world file

Original Extraction

• starting with big island elevation and vector data
• loaded the USGS 10m DEM, extracted an area at (239176.4, 2218879.3), ( 6196.2, 6447.7)
• by loading the hydro DLG and comparing the shoreline, there is a big visible offset between the DLG and DEM data
• measured the offset with the Distance tool:
  • 430, -380 meters
• used "Layer - Offset Coordinates" to move the road and water layers to line up with the DEM

snapshot of elevation, road and water data in VTBuilder

• loaded the USGS DRG into BExtractor and extracted the building locations

DRG and extracted buildings in BExtractor

• examined some aerial photos of the area

aerial 1, from a poor photo of a wall print

aerial 2, flatbed scan of a print from Air Survey Hawai`i

• had some trouble aligning the buildings to the other data

Honokaa Resources

• Melvin Ah Ching's Honoka‘a Online & Photos Website

Ahualoa Imagery/Roads

• Like the rest of the wet parts of the island, it is a difficult place to get imagery data for.  Even Google  had substantial cloud cover until 2010, and as of 2011, there's still no aerial, just poor-quality space imagery.
• Most of Ahualoa is in the Honokaa USGS quad, but the western part is in the Kukuihaele quad.
• Road data source:
  1. USGS 7.5" DLG (honokaa and kukuihaele, presumably in NAD83)
     • Quality isn't that bad.  There are some spurious driveways, but it follows the actual main highway pretty well.
     • There is only one notable spurious road: a straight connector from west Puaono uphill to the highway.  It's very surprising, because it doesn't appear in the DRG topo map which is the source of this DLG.
     • There are also cane roads, which once existed but are gone today.
     • Mostly, it suffers from lack of completeness and timeliness.
  2. Tiger 2010 - roads available as Shapefile (tl_2010_15001_roads.zip for whole island)
     • Quality is very bad.  It only agrees with reality on the main road.  All side roads are bogus, and there are hundreds of spurious driveways.
  3. OpenStreetMap, which as of January 2011 was identical to Tiger 2010.
• Closed road data, for comparison:
  • Google (map and earth).
    •  Does not match any of the public datasets, but it is not better quality either.  It has Puaono Rd. going all the way through.
    • There is a major collision between streetview of Ahualoa (apparently every road) being "snapped" to the terrible roadmap, so that many roads are missing from streetview, just because the roadmap didn't contain them.
  • Microsoft (bing)
    • Does not match any of the public datasets.  It is probably the most accurate, as of January 2011.  Like the DLG, it matches the curves of the tax map fairly well.  Like Google, it has Puaono Rd., but it also has Kapena (called "Homestead") going all the way up to meet the west end of Puaono.
    • Interestingly, there are excellent oblique aerials covering a few parts of lower Ahualoa, and apparently all of Honokaa!  Unfortunately, the Bing interface doesn't indicate where the oblique coverage exists, so it it s tedious process of panning around to find the area.
• February 2011, i personally corrected all the OpenStreetMap roads in Ahualoa (and most of Honokaa and surrounding towns).  So, now OSM is far more correct/complete than any other source.  December 2013, I did another round of major improvements to Honokaa OSM including many of the building footprints.