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calibrating FAA aviation sectionals

Posted: Tue May 22, 2007 6:33 pm
by rmandel
I'm trying to calibrate an FAA avation sectional (Dallas Ft. Worth) chart. At the top of the chart it says.

Lambert Conformal Conic Projection. Standard parallels 33 20' and 38 40'. Horizontal datum: North American Datum of 1983 (wgs 1984).

The entire chart is 70MB so I'm not attaching it.

I'm a little confused about what I enter for
Lat_0:
Lon_0:
Lat_1:
Lat_2:
X_0:
Y_0:

I'm guessing Lat_0 and Lat_1 are 33 20' and 38 40 respective. I have no clue about the others.... especially "flase origin". Once I enter these parameters do I still need to enter the calibration points?

Any help would be greatly appreciated.


Regards,

Richard

Posted: Thu May 24, 2007 9:23 pm
by Scott
It may not be necessary to calibrate using a projection.
You only need 3 known points on the map for an accurate calibration. Most of aeronautical sectional maps provide the lat/longitude lines on them. You can use the intersection of these lines as the reference points.
In Map Manager, use the "Known Points (Skewed)" projection type.

If the map is a wide area LCC map then you would need to use the LCC parameters.

If you need LCC, There is some detail on LCC parameters in the Map Projections manual at http://pathaway.com/mapproj.htm.