Ben's House

I'd like to give a virtual tour of my house - from the native trees along the driveway to the shoji drop-ceiling that casts a soft light into the center of the house.

The architect, Gordon Motta, kindly gave me a copy of the blueprints for the house. There are a several plan and elevation views, and even detailed materials lists. However, I've learned it takes years of knowledge of architecture and construction in general to make sense of a blueprint - not all the 3D positioning and placement info is there, mostly it is left assumed.

Location

From looking the USGS topo DRGs, it looks like the house is at (UTM zone 5 NAD83: 237620, 2219325), which is 20°03'11" N, 155°30'30" W.  We can guess that elevation is around 750 meters because there are two contour lines passing near the property: the 2480' (755.9m) line at the southwest corner by the pond, and the 2440' (743.7m) line at the base of the driveway:

In Google Earth, using their imagery from December 2009, it's at -155.508362°,  20.053239°.  Previous imagery (2003) was shifted around 8 meters off from the 2009 image.

The Land

2.305 acres in a long L shape.  USGS 10m DEM, because it is derived from those two DRG contours that barely approach the land, lacks sufficient detail to get even a rough idea of the elevation of the parcel.  Surveying would be necessary to get elevation contours, but this could easily cost several thousand dollars.

In 2000, i tried using a consumer GPS to walk the property bounds and establish some major features such as the house corners and some larger trees.  However, the GPS device never got better than ~5-7m accuracy, probably due to the numerous trees present, and the results were generally not useful.

In 2002, i tried doing some manual surveying with a level and horizontal ruler, measuring along some lines in the SW corner.  Very labor intensive, and very limited because you have to be able to actually walk along these lines, and the land is too overgrown for that.

In February 2011, i used an IP-S2 system to laser-scan the land from the back of a truck.  The data is only collected near where the truck could drive, but this is roughly half the land.  The GPS trajectories are very accurate because of DGPS and IMU.  Relative to it:

• The Google Earth imagery from 2003 is off by ~9 meters SSW
• The Google Earth imagery from 2009-12 is off by ~6 meters SW.

There is an issue with vertical (elevation) coordinates.  According to a very accurate (OPUS) point measured just in front of the upper garden gate:

 REF FRAME: NAD_83(PACP00)(EPOCH:2002.0000)       ITRF00 (EPOCH:2011.1024)
        X:     -5455176.415(m)   0.029(m)          -5455177.372(m)   0.029(m)
        Y:     -2485079.832(m)   0.022(m)          -2485077.310(m)   0.022(m)
        Z:      2173499.339(m)   0.029(m)           2173500.362(m)   0.029(m)
      LAT:   20  3 11.65139      0.033(m)        20  3 11.68458      0.033(m)
    E LON:  204 29 29.08736      0.010(m)       204 29 28.99474      0.010(m)
    W LON:  155 30 30.91264      0.010(m)       155 30 31.00526      0.010(m)
   EL HGT:          773.960(m)   0.030(m)               774.146(m)   0.030(m)
 ORTHO HGT:          752.566(m)   D.N.E. [No official datum supported (FAQs 19,20).]

This "ortho hgt" value (orthometric) agrees very well with the USGS DEM:

• The GPS antenna was 1.689 meters above the ground, so that's 750.77 meters (orthometric) on the ground.
• USGS DEM from loosely interpolated contours give 751.5 meters at that spot
• Commercial (Intermap/NEXTmap) LIDAR gives 750.8 meters at that spot, astonishingly close.

Trajectory of truck IMU at a reference point on driveway: 773.4 m (vs. ellipsoid)
Height of truck IMU above ground: 2.1 m
Height of ground measured by GPS/IMU: 771.3 m (vs. ellipsoid)
Height of ground from LIDAR: 750.0 m (vs. geoid)
Difference (ellipsoid - geoid): 21.3 m
Difference (IMU - geoid): 23.4 m

House Modeling

1. ideally, there would be a "homebuilding wizard"
   • would let you describe your home in general terms
   • it would build the house, completely describing the structural elements like bricks and boards, and output the result into a realtime rendering environment
   • there are a few standalone packages like this on the market, but do they let you export the building?
   • so far, it looks like the answer is no.
   • i produced a procedural model using the VTP building support which looks OK, but interfaces poorly with the ground, since the elevation is wildly imprecise
2. second choice would be to use a general-purpose 3D modeling program to model and render the house
   • 3D Studio MAX is fairly easy to get a hold of, but it's not easy to use for architectural work
   • it does support using English units (since version 1.2)
   • i started out use MAX to enter the floor plan as 2D lines, then
     • created a "box" entity for the floor of each room
     • used "extrude" to create 8' walls
   • but.. walls should have thickness - this gets awkward very quickly.
   • i'd rather start from the "ground up" - start with the foundation, then the main support posts, then the floor, much as carpenters would when building the house.   However, it's not clear what shape the foundation is from the blueprints - it mainly follows the topography of the terrain (a gradual, but significant, slope).  I don't have this topography information.  Where to start?
3. third choice would be to use a full, traditional CAD/drafting program
   • e.g. AutoCAD, FormZ
   • would require a lot of learning and a lot of labor
   • somewhere between options 2 and 3 is 3D Studio VIZ

Source Materials

what i have to work from:

• blueprint diagrams
  • printed on large-format paper
  • how to digitize them?
• detail diagrams
  • printed on 8.5"x11" paper, easily scanned - see example:
• measurement of the existing house

Construction Details

• 12/99, i asked people familiar with the house's construction how it was done.
  they said it uses standard post-and-beam construction, starting like this:
  1. bulldozer: carve the driveway and carport
  2. put in the "batterboards", stakes in the ground at the right places
  3. tie strings between the stakes, use levels to make sure the strings are level
  4. shovel the flat areas for the footings
  5. pour cement for the carpool and footings
  6. lay the "pier block" on the footings - this is a piece of cement, pre-made, which provides a base for the 4x4s
  7. add the 4x4s for the main support posts
  8. add 4x8s across from post to post
  9. add braces to the 4x4s, surface nailed to the 4x8s
  10. add "floor joists", 2x6 or 2x8 or 2x10 (usually 2x8), spaced 16" apart, standing on end, nailed in at 45º ("toenailing")
  11. add "blocking" between the floor joists
  12. plywood, covers the floor
  13. add 4x4 posts and top beams (4x8s and 4x6s)
  14. a bunch more steps (need more info)
• boards
  • problem: sizes like "4x4" aren't actually 4 by 4 inches!  What are the actual sizes?
  • the answers are in this table
• cement blocks
  • common blocks are 6 x 8 x 16 inches
  • actual dimensions are 3/8" shorter than this, in each direction, to allow for 3/8" of mortar
• building lines
  • houses are often designed on a grid of regularly-spaced lines, e.g. 8' or 10' apart
  • this leads to a set of "building lines" used as a reference while building
  • in physical construction, actual strings are strung from the batter boards along these lines
  • around the edge of the building, the lines determine the outside of the blocks and beams of the wall
  • inside the building, the lines determine the center of the blocks and beams that support the floor

Tax maps

• see a description of tax maps
• my house is on a tax map labeled "Third Division, Zone 4, Sec. 6, Plat 09"
• adjacent maps are Plates #07, #08, and #10
• County website now has Tax maps online; link is to h46009.tif; my land is the funny L-shaped parcel labelled "45"

Other useful data might be available in the Hawai‘i County 1997 Data Book, found on the County of Hawai‘i site.