A GIS Publication by Mentor Software, Inc. |
Customer Profile: HP & Associates
HPA Elevation Data Model for Riverside County
H.P. & Associates offers services including high-quality computerized
mapping, demographics, data exchange, programming solutions, and full on-site computerized
GIS automation solutions.
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Take the Trivia Challenge! Answers at bottom of page
1. Which geographer and mathematician was first to assign latitude and
longitude on his maps. Hint: He's older than Ptolemy.
2. What's a NURB and what does it have to do with CAD? Hint: It's
not Dr. Suess character.
3. What did John Harrison invent in 1736 and why?
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Trivia Answers:
1. Marinus of Tyre, the founder of mathematical geography lived in the 2nd century A.D.
2.Non-Uniform Rational B-splines (NURBs) are used by nearly all 3-D CAD
systems to define surfaces. Not only do they minimize data stored without loss of
information (in contrast to arc or line segment interpolation which is data-intensive and
does not scale), they are also powerful in representation of conic sections. Each
NURB curve is defined by a set of control points (x,y,z,w) and a knot vector (0.0, 1.0,
2.0, 3.75, 4.0, 4.25, 6.0, 7.0), which are fed into the basis functions that determine the
shape of the curve. Each segment of the curve is basically a polynomial of degree k,
defined by k surrounding control points. Splines are continuous curves based on a
set of control points. Note there are various mathematical techniques for accomplishing
this. See http://design.mit.edu/j_yu/2.131/History.htm
for more information.
3. A £20,000 prize, offered by the British government inspired Harrison to
invent the Chronometer. It was invented to keep sailors from being lost at sea. For more
history, read William J H Andrewes, Quest for Longitude, Collection of Historical
Scientific Instruments, 1996, URN 14393, E1
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|
Letter from Norm
-The Windows battle is over!
Freebie of the Month
-State Plane Locator
GIS Tips
-Coordinate Systems Part IV, Latitude
Ask Norm?
Question 1: How does the ellipsoid relate to
sea level?
Question 2: I tried Forward/Inverse and got
some weird results. Is there some flakiness in your program?
Readers Respond
-Regarding the vara
-Freebie of the month idea
GIS Resources
New! Space Imaging. Check out
their picture of the week (Oklahoma
City Tornado Path), Kosovo
coverage, and satellite
buzzwords.
New! GIS Landbase Web Site This is great GIS
resource managed by Rick King. He supplied us with the data for our State Plane Zone Locator.
New! Earth Viewer from various
satellites View the Earth as currently seen from a satellite in Earth orbit
New! The History of Cartography Project
From the University of Wisconsin
New! Measured and Estimated Seafloor
Topography
Products
Multric and Hawkeye
are both AutoCAD 2000 Compliant. Attention R14 Users: Download
your FREE upgrade!
New! Marinus
1.01 (formerly DLG2DWG)
Marinus converts USGS DLG data to AutoCAD drawing file (i.e. .DWG) format. Marinus
is capable of producing the resulting data file in any defined coordinate system,
regardless of the coordinate system upon which the source data is based. |
