Mobile Crossing WayPoint Map Loader Betreibershandbuch PDF herunterladen (Seite 80)

02-03-2010 16:17:26

This report is made every time you calibrate conversions. It contains information on the extents of the area covered by the calibration

Waypoints and the calibration data found.

The area that calibration was performed over is bounded by:

Maximum Latitude: 29 35.104

Minimum Latitude: 29 24.338

Maximum Longitude: 84 42.09

Minimum Longitude: 84 29.33

CONVERSION ACCURACY

At the center of the area considered, for the 2 primary slave stations;

The spacing of 7980 W lines per 0.1 microseconds is: 102 feet

The spacing of 7980 Y lines per 0.1 microseconds is: 52 feet

You cannot expect better accuracy than half the larger of these distances in the conversions.

First Pass. If some Waypoints are removed from the calibration process,

there will be another pass.

Slave: 7980 W Mean ASF: 0.56, Variance: 0.054

Slave: 7980 Y Mean ASF: 0.61, Variance: 0.106

The calibration Waypoints are now used to judge the accuracy of the calibration and subsequent conversions. Each calibration Waypoint

is converted to Lat&Lon using only the TDs and the calculated Lat&Lons are compared to the actuals. A miss distance is then found for

each Waypoint and all miss distances are averaged. The worst case miss is also reported. Next, the loran numbers are calculated from

the Lat&Lon for each Waypoint and compared to the real loran numbers.

The following are the individual miss distances and TD errors.

Look at the end for the average and peak miss.

Distance Error @Bearing TD1 error TD2 error Waypoint #

28 ft. 75 -0.02 0.02 1

110 ft. 283 0.06 -0.16 2

87 ft. 82 -0.07 0.09 3

90 ft. 63 -0.08 0.04 4

45 ft. 81 -0.03 0.04 6

Average distance error: 72 ft.

Peak Distance Error: 110 ft. on Waypoint #: 2

In examining the report above, I note that point 2 is diametrically opposite the other 4 points that seem clustered. That

looks a little bit suspicious. The optimal solution is when all the points scatter randomly in bearing and distance. You

might consider throwing that one (#2) out and calibrating again. However, the results above are acceptable as is.

The Calibration selection screen additionally allows you to examine the ASFs of both the government and user

adjusted tables for your area. This will better inform you as to the ASF values that will be used and to give you a feel for

the variability of the values over your area. In some areas, the ASF values are very uniform across the area and a single

value (method 3) will be a good choice. In other areas, the ASF values vary widely from place to place and you will be

better off using the user-calibrated tables (method 1). If there seems to be no table page for the point you are converting,

you have to use method 3. The example below for West Lake Huron shows an area where the values are not uniformly

distributed. The tables are in 5-minute increments that equate to about 5 nautical miles. This table shows a jump from -

2.5 to -1.0 microseconds in 5 miles. That could introduce a half-mile potential error.

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Mobile Crossing WayPoint Map Loader Betreibershandbuch Seite 80