Hawai‘i Island Satellite / Aerial Imagery

• See also: Hawai'i Statewide Imagery and VTP Collection of Hawaii Emerge Tiles
• The USGS Clearinghouse: Hawai'i Island site has the merged Emerge-USDA aerials (571 MB, see Statewide Imagery for description)

Overview

How much memory is needed to cover the island (130 km * 150 km) with texture images?

Resolution	Texture Size	Memory Needed			Notes
		16 bit	24 bit	32 bit
~4m	32k x 32k	2 GB	3 GB	4 GB	need some tiling/paging to support this
10m	13000 x 15000	371 Mb	558 Mb	744 Mb	bought bad SPOT data at this resolution
20m	6500 x 7500	93 Mb	140 Mb	186 Mb
25m	5200 x 6000	59.5 Mb	89.25 Mb	119 Mb	bought good LS7 data at this resolution
~32m	4096 x 4096	32 Mb	48 Mb	64 Mb	limit with a 64Mb graphics card

Satellite:

• in November 2007, made a fresh attempt to get a properly georeferenced image from the 2000 Imagelinks delivery
  • Manually rectified the imagery to align with the USGS 10m DEMs
  • Extracted area: size 134275 x 153300, west 177070 north 2244740
• in June 2004, bought GeoCover NaturalVue data for the state of Hawai‘i (see Statewide Imagery)
  • however, although it's 15m pan-merge, the image quality isn't as good as the 25m LandSat we acquired before for the Island of Hawai‘i.
• in September 2000, acquired good LandSat7 imagery from ImageLinks Inc.
  • since the original data is public domain, there are no redistribution restrictions, as there were with the SPOT images
  • image was delivered at 25m resolution, with <2% cloud cover, which was erased manually in PhotoShop to produce a cloud-free image (to the right)
  • a pan-merge was also done to produce a 15m image, but color quality was too far from visible-light to be useful for visualization
  • a 32m/36m subsample of the image (4096*4096 for the extents of the island) became part of the VTP distribution
• older attempts at acquiring images

Aerial:

• Old imagery: greyscale OrthoQuads from 1977-1978
• Several of the statewide aerial sources (Air Survey Hawaii, USDA Emerge, NOAA/NOS) include coverage of the Big Island
• HawaiianImages.net
  • Professional photographer Brian Powers has a large number of oblique aerials of the Big Island on his site, browsable in small size, potentially useful as reference photos for terrain modeling.
  • Incredibly, the entire coastline is available!  Examples:
  • 

Air Survey Hawaii

• April 1999 bought the following big island images from Air Survey Hawai‘i:

  • Area	Date	Scale
    Puako to Kawaihae	12-2-82	1" = 2000'
    	9-9-92	1" = 3000'
    Waipi‘o Valley	12-2-82	1" = 2000'
    	9-9-92	1" = 3000'
    Honoka‘a	9-9-92	1" = 3000'
    Kilauea (just north-east of)	10-11-91	1" = 2000'
    Kealakekua Bay	11-14-91	1" = 2000'
    Hilo	2-7-98	1" = 2000'

  • 1"=1000' = 304.8 m = 1.02 meters/pixel @ 300 dpi, 0.76 m/pix @ 400 dpi
  • 1"=2000' = 609.6 m = 2.03 meters/pixel @ 300 dpi, 1.52 m/pix @ 400 dpi
  • 1"=3000' = 914.4 m = 3.05 meters/pixel @ 300 dpi, 2.29 m/pix @ 400 dpi

Image Quality:

• SPOT pan-merge imagery of the island has very poor color quality
• Aerial is much better quality, but has problems of it's own: limited coverage, more clouds, and lack of georegistration.
• Diminishing returns: the 10m SPOT looks only marginally better than 40m SPOT, despite the 16x more resources consumed.

This is SPOT data, 20m color merged with 10m panchromatic, resampled at ~15m/pixel:

This is NASA high-altitude aerial photography of the same area at ~15m/pixel: