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Data Type Map Projection Datum Vertical Units 1-degree DEM Geographic (arc-seconds) Old Hawaiian meters 30-meter DEM UTM (meters) Old Hawaiian meters (some are in feet) 10-meter DEM UTM (meters) NAD83 feet
1°
DEMs
- number of files for the whole island: 5
- free from the USGS web site
- at 1200x1200 data points per degree, it's 1506x1630 data points
- ~86m/point (3 arc-seconds at this latitude)
- using 64x64 point patches, produces a 25x25 grid = 625 LOD patches
- poor quality: major gridding artifacts, entire island is offset by up to 1 km east, etc.
- number of files for the whole island: 82
- cost around $600 from the USGS ESIC on CDROM (what i paid in 1997)
- now much cheaper, the USGS had a major price drop
- at 30m per point, about 4300x5000 points = 20 million vertices = 40 million tris
- much better accuracy than the 1° DEMs
- 99.01.15: extracted at UTM origin and size (176793, 2091648),
(134137, 152721)
- extents LTRB (176793, 2244369, 310930, 2091648)
- subsampled to 1k*1k and 2k*2k
- 99.09.16: extracted a 4k*4k subsample at the same location
- available for the whole island - both from the usual USGS Sources and from UW 10m Data
- 13000x15000 points = 195 million vertices = 390 million triangles
- ordered and received - quality is incredibly good
- quality comparison:
30 meter
10 meter
- 00.01.12: extracted an 8k*8k sampling from the 10m DEMs - that's 16.2m resolution!
- 04.05.08: went back to 10m DEMs to extract a fresh set of BTs at
WGS84
- Had to shift the extents to match the imagery
- New origin and size: (177093, 2091478), (134137, 152721)
