Notes From 12/13/05 Digital Orthoimagery/DEM Workshop
Wish List Discussion:
Bureau of Census needs:
Orthoimagery for road centers and populated areas at 1.25
meter accuracy. This is needed to
accurately locate rural road network and identify structures along the roads. Highest priority areas are southeast Alaska, Denali Borough, and the Cold Bay region.
State of Alaska DGGS top priority needs:
1) Natural gas pipeline corridor: orthoimagery and DEM’s for geologic resource analysis with 5-10-meter accuracy
2) Tsunami communities: orthoimagery and DEMs to identify inundation zones, sub-meter accuracy. Communities needed in order of priority: Sitka, Sand Point, Unalaska, Yakutat, Whittier, Cordova, Valdez, Adak, King Cove, Nikolski, Ouzinkie, Perryville
3) Active volcanoes: Orthoimagery to make hazard assessments; 5-10 meter accuracy would be adequate in a 20-km radius around each volcano
4) Mineralized areas: Orthoimagery for Interior Alaska uplands, Donlin mineralized area in southwest Alaska, Pebble mineralized area in southwest Alaska, North Slope/Brooks Range foothills
State of Alaska DGGS medium priority needs:
1) Corridor 25-km wide on either side of proposed natural gas pipeline corridor: orthoimagery with 5-10 meter accuracy for resource mapping
2) Corridor 25-km wide on either side of existing roads and railroads: orthoimagery with 5-10 meter accuracy for resource mapping
3) Norton Sound/Kotzebue coastline
4) Kuskokwim/Yukon River drainages
5) Tanana, Kobuk, and Koyukuk river drainages
6) Kenai lowlands across to English Bay/Nanwalek
7) Lower Matanuska-Susitna Valley
8) Kuskokwim mineral belt
9) Seward Peninsula
10) Red Dog/Kobuk River drainage
11) Bristol Bay/Alaska Peninsula
All of the above require
orthoimagery at 5-10 meter accuracy for geologic hazards mapping, natural
resources mapping, erosion studies, and energy-related studies
State of Alaska DGGS low priority needs:
1) All coastal communities not covered by tsunami studies
2) Nenana Basin
Factors in Setting the Priority for Products:
Discussions on how we would determine priorities revealed
that the factors below would be considered.
Overlap: areas showing overlapping needs by two or
more agencies
Economic development for the state
Health and safety
Funding: where funding is available
Other needs
When all requests for products are received, new maps will
be distributed. Where high priorities
and overlapping needs are identified, the agencies involved will meet again to
determine priorities and identify funding. The AGDC Orthoimagery Subcommittee will coordinate the meetings and
provide technical information as needed.
Ways to contract:
From discussions in the workshop, below are Federal agencies
that have staff and experience in contracting orthoimagery and DEM type
products.
USGS
NASA Stennis
USDA FSA Aerial Photography Field Office
USDA Foreign Agricultural Service (ASCS 8A)
Urban and Rural Alaska Specifications:
Workshop participants divided into two groups to develop
data specifications for rural and urban areas. Below are the specifications. Statewide specifications were not addressed.
Rural Imagery and Elevation Data Standards
The group agreed that the specifications outlined in the
April 2005 RFI under “Orthoimagery Specifications for Special Interest Areas”
and “DEM Specifications for Special Interest Areas” were sufficient for rural
areas, transportation corridors, etc., that did not have the requirements of
the urban areas
Urban Imagery & Elevation Data Standards
Draft Version 1.0
Compiled on 12-13-05
Participants:
Charlie Barnwell (Anchorage); Bruce Simonson (Juneau); Bill Holloway/ Marvin Rude (Kenai
Peninsula Borough), Erick Johnson (Mat-Su Borough), Carol Barnhill
(AK Dept of Fish & Game-Anchorage), Kim Homan, (Bureau of Indian
Affairs-Juneau), Robert Ruffner/Stephanie Sims, Kenai Watershed Forum
Introduction
The following is the result of an hour long group
discussion/brainstorming session regarding 1) definition of “urban” and 2)
requirements of urban areas for imagery and elevation data.We recommend refinement of this
document.It may be advisable to follow
the recent successful statewide effort where BLM, NPS, ADNR used a Request for
Information (RFI) to collect vendor information regarding requirements and
standards.
Urban Definition
What makes an urban center or urban area? In Alaska,
this is somewhat problematic given the contrast of huge areas of wilderness,
small villages and towns, and a few major cities. Following are key:
|
Distinguishing urban characteristics
|
Feature
|
Population
|
|
Planimetric features
|
Building footprints
|
Village/town to city
|
|
Roads
|
Road network
|
Typically city
|
|
Transportation corridors
|
Pipeline, major road, electric, gas, etc.
|
Rural areas to city
|
Hydrants
|
Point features
|
Typically city
|
|
Sewer line
|
Sewer line network
|
Typically city
|
|
Point address
|
Point features representing situs addresses
|
Typically city
|
Semi-Rural
In Alaska characterized by:
- Native allotments
- Some public buildings, e.g. school, post office
- Pipeline corridor
- Port (harbor)
- Airport or airfield
Wilderness
Large areas with no concentrated centers of population.
Horizontal Resolution Requirements
|
Requirement |
Ideal |
Minimum acceptable |
|
Overall
|
6 inch
|
60 cm
|
|
Ground Control Points (GCP)
|
Centimeter (sub meter) resolution acquired w/ licensed surveyor
|
Same resolution GCPs captured without surveyor
|
|
Reference GCP (less stringent)
|
Map grade w/ base station
|
Map grade, e.g. ProXR
|
|
Adequate Density of GCPs
|
1 per 5 square miles
|
|
Vertical Resolution Requirements
|
Item
|
Ideal
|
Settle for
|
|
Control
|
RTK GPS points and traverses for DEM
|
Network of planimetric or GPS control points
|
|
Preliminary engineering
|
2 feet topo
|
4 feet topo
|
|
Planning
|
2 to 4 feet topo
|
4 feet topo
|
|
Engineering
|
2 feet topo
|
2 feet topo
|
Vertical / Elevation Data Requirements
|
Requirement
|
Ideal
|
Acceptable
|
|
Geoid definition
|
|
|
|
Flood zones
|
2 ft contours
15 cm RMSE
|
|
|
Drainages
|
4 ft contours
|
|
|
Control
|
|
|
LIDAR
|
Requirement
|
Ideal
|
Acceptable
|
|
Flood zone mapping
|
|
|
|
Vegetation/land cover
|
|
|
|
Planning
|
|
|
|
Preliminary engineering
|
|
|
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Urban Feature extraction
|
|
|
Imagery Requirements
| Item |
Ideal |
Settle for |
Frequency of acquisition |
Orthoimagery
Natural color
|
Resolution 6” |
0.6 meter or 2 feet pixel |
2 years for 0.6 m
10 years for 6 in. |
|
Multispectral imagery
|
7 band
|
4 band
|
2 years for 4 band
5 years for 7 band
|
|
Digital elevation model (elevation data)
|
|
Once every 10 years
|
Once every 5 years
|
Urban priority Criteria
Discussion regarding what criteria should be used to
prioritize the funding of imagery and DEM collection.
- large population areas (>10,000 population)
- High growth area, e.g. (Wasilla—Palmer area)
- Natural hazard areas
- (wildfire, earthquake, tsunami, avalanche, flood)
- Area with natural resources sensitive to development
- (wetlands, anadromous streams, old growth forest, etc.)
Licensing: public domain
Cycle: 5 – 10 years
Deliniation of Rural and Urban Areas
Shapefiles outlining the areas needing orthoimagery and DEMs
will be created by each agency. A blank
polygon shapefile containing the attribute fields listed below will be created
by USGS and send to agency contacts.
Attributes to be collected:
Name of project or area
Requesting agency
Agency priority: high/medium/low
Agency sub-priority (if applicable)
Reason needed
Initiatives supported (if applicable)
Specifications: rural/urban
Funding available: dollar amount
Date needed
Acceptable dates of image collection
Point of contact: name/phone/e-mail
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