| Where do you
get the depth information and is it accurate? |
|
Depth
information
is provided by the Department of Natural Resources (DNR)
for each state or the USGS for some selected major lakes.
Some of the depths have not been updated since the 1930's and should be
used with caution. You should NOT use these depths for Navigation.
|
| Are distances in the images correct and
what is the spatial reference? |
|
Distances in the images
are relatively correct to the
limitations imposed by the current limitations of digital geo-spatial
technologies. Although significant effort has been made to maintain the
accuracy of the original source images, all geographic images have
limitations due to the scale, resolution, date and interpretation of
the original source materials. In no event shall the creators,
custodians, or distributors of this information be liable for any
damages arising out of its use (or the inability to use it). See
"Liability Statements" for additional information.
For both the image and the
height/depth contours the Horizontal Coordinate Scheme is UTM, the
Ellipsoid is GRS80 and the Horizontal datum is NAD83. North
is always at the top of the image.
|
|
What is the source of the
images and the
original resolution? |
|
The majority of the images
are based on the
"National Agricultural Imagery Program (NAIP) Digital Ortho-rectified
Images (DOQ) and where taken the US Department of
Agriculture’s Farm Services Agency, Aerial Photography Field
Office. The original images were taken from approximately 20,000 feet
and the majority are 1M resolution (Iowa and parts of St.
Louis County in Minnesota around Ely are 2M resolution).
The images in the Twin Cities area were from the US Urban
Imaging program and are 2 foot resolution.
The images are further processed by combining them with
USGS contour information for accurate shading to give a 3D effect and
then correcting the anomalies that are common in most aerial photos
(visible merge lines, tonal differences, water sun "glint", etc.).
Finally depth information is superimposed on the
image displayed as
shaded contour lines to give a 3D effect to match the rest of the image.
|
| When
where the images taken? |
|
The original photographs
were in the late summer with
full leaf-on during the following years:
- Idaho - 2004
- Indiana - 2003
- Iowa - 2005
- Minnesota
- 2003 (except Twin
Cities)
- Twin Cities 2002
- Missouri - 2005
- North Dakota
- 2003
- South Dakota
- 2004
- Texas - 2005
- Wisconsin
- 2005 (except Dane County, taken in April 2005)
|
|
What print sizes are available
and how
are they printed? |
|
Standard
prints are:
- 9" by 12"
- 12" by 16.67"
- 16.5" by 23"
- 20" by 28"
- 23" by 32"
- 30" by 42"
All prints have a 1 inch wide white
border around the entire
print. Images are printed at 1400 DPI
using 4 passes giving an effective print resolution of 300 DPI.
|
|
What print media do you use
and how long
should the prints last? |
|
Images
are printed on Premium-Luster Photographic Paper using
pigmented
inks. Prints have a rated life
indoors under glass of 50+ years (based on simulated aging in a lab),
longer than most photographs (testing by www.wilhelm-research.com).
|
|
How do you laminate the images
and when
should it be used? |
|
We
cold laminate with 3 mill gloss laminate and a 1/8 inch sealed
edge. Although these prints have excellent longevity (see
above), all prints are affected by exposure to light and damage from
handling. If you are not planning to have your print mounted
and framed, you should have it laminated to minimize fading and
potential damage from handling.
|
|
What is the resolution of the
JPEG files
and what compression do you use? |
|
JPEG
files are 3000 by 2150 pixels at a minimum and where saved using
compression level 3. Color profile is embedded and is sRGB
(IEC61966-2.1).
|
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